A Forum run by Enthusiasts of MidNite Solar

Robin, very interested in the history of your excellent Spectro Acoustics audio gear line from the 70's that you produced. I have most if not all of the models you made and they have been in daily use now for almost 35 years! No repairs ever needed etc. The 500SR amp being my favorite!

(http://midnitesolar.com/smf_forum/index.php?action=dlattach;topic=474.0;attach=256;image)

robin did that? very nice stuff. i'd like to hear this too.

I will point Robin to this thread it will be a fun story I am sure.

Very high quality manufacturing and designs. They have stood the test of time, a LONG time! Clearly anything Robin & Bob get involved in is never second rate and made/designed to last! OK boys, there's a bunch of flowers for ya, how about the whole story on Spectro? Or at least as much as you can remember....:) Spider Man, Pink Lady etc.

First pic was the back of their EQ brochure. This is the front.

I wish I knew how to post pictures here? Maybe Ryan can show me. Bob has some pictures of Spectro, but I still have a bunch. The history is quite interesting as it happened in a fun time when bob and I were still young. I started my electronics career in 1971 working for Bob Carver. Heard of him? He was the brains behind Phase Linear and the Carver Corporation. Bob's partner at Phase was Steve Johnston. One of the guys working with me at Phase was Ken Cox. Ken and I got tired of waiting for Phase Linear to come out with their Phase Linear 1000 preamplifier, so we built a simple preamp ourselves. We built 23 of them because lots of our friends wanted a preamp so they could really use the Phase 700 watt amp, just like Kan and I. By the way Bob Ca and Steve J were a couple of the people that bought these home made preamps. Turns out they were pretty good. I even still have one. A dealer from Canada was down visiting us at Phase and saw our little preamp. He said he could sell them if they were available. That was the statement that made Ken and I start Spectro Acoustics. By the way, Ken Cox and Steve Johnston went on after our HI-FI career to found Trace Engineering while I was designing nuclear cruise missile launcher power supplies. I was a whopping 21 years old while at Trace. When Ken and I started Spectro, one of our first products was the RobKen 2123. The model number came from our ages.
I have to go to a convention at the moment, so will continue this later.

interesting stuff. i am supposing there weren't any ics in those preamps as ics were still fairly newerish, if that's a word, and the ones that were available commanded a bit of cash compared to their discrete counterparts. i'm curious as to why you did not continue the audio endeavor even after the service? right now you could throw together a good tube stereo amplifier and make a killing as there are audiophiles out there that love them. not sure what a nice solid state amp's reception might be, but they both run rings around the ic pas they have now.

it just occurred to me that both you and boB could have the same nickname with rob. that's wild.

maybe you guys could start a history like section. it is something that many of us do not think about until long afterwards and we start saying to ourselves that i wish i had saved that or marked that down. there is much history to be had and it's all worthy of at least mentioning to some degree. include any present employees with their own if they wish to as well. ok it doesn't all have to go on the internet, but would still be good to do anyway.

Here is one link to a short version of the history of PWN inverters written by Robin...

http://www.hardysolar.com/inverter/inverter-history.html

boB

Quote from: Robin on February 08, 2012, 12:10:57 PM
I wish I knew how to post pictures here? Maybe Ryan can show me.

In Firefox and Chrome my attached images do not show up in preview. After hitting post, they do. Had me confused at first but then I just went for it! Are you hitting additional options and then browse for the images?

boB, I know Robins version of the Spectro Pre-Amplified planter box. Would like to hear your version....  :)

Awesome history!

very good reading and it kind of makes me see there were so few doing this for the industry. kudos for your insight and efforts. had i known you guys back then i'd have probably wanted to join you in some capacity. i had one of those buzzing tripplites in the 80s too.

i, also, have a different view of you robin as i now believe you humbled yourself into a bit of a backseat before from my perspective and i now know better. no offense is meant as all i'm saying is i now have a better concept of your abilities and accomplishments. i'm also sure many out there feel the same. it only serves to better the company/customer relationship unlike dealing with a cold conglomerate.

my thanks to you for posting that boB. got any more?

Am I the only one that keeps a box in the closet for 32 years? And the receipt + the owners manual? It is a good box......:)

Hey boB, maybe this will jog your memory on the rare Spectro Pre-Amplified planter???? :)

Those are GREAT pictures !!

I will have to post a few of what I have too.
I DO remember the planter box !   One thing that was neat to see was your picture of the Spectro cardoard
box.  I had forgotten what they had even looked like !

PS, Niel...   Robin's stories are pretty right on. There were a few northwest companies that were all related to
those early stories.  Greg Mackie of  TAPCO, Audio Control and Mackie Designs (now LOUD technologies), as
well as RANE  Symetrix and Carver Corporation for a few of the audio companies around here.
Robin and I spent quite a while with audio companies.

boB

I don't know what the actual preamp planter box was that Robin made way back when, model etc.? The one pictured was done a few years ago by me. That preamp is a P303 that you or Robin gave to your dad and sometime around 2000 or so he was no longer using it and sold it to me. He was in the neighborhood and delivered it right to my front door. Customer service obviously runs in the family!

The planter pic was "staged" and it still works just fine. I fire it up and drive a 202 amp with it once in awhile.
I alternate between that and a Spectro 217 preamp driving a 500SR when I want to "feel" the music! Have some Carver gear as well, C-1 preamp, PM350 amp etc.

Those 5 year warranty things really are a habit you guys have. Back then and today too!

One of my favorite non tube glow in the dark Spectro amps. Model 202.

Warning! Nudes ahead.......A look inside the 202 amp. Some of the magic smoke escaped from one of the caps so a previous owner whipped out some Zip ties and glue to mount newer, but much smaller physical size caps piggy backed on the originals. May not be pretty but they work fine so I'm leaving them alone...for now.  :)

Next up a 217R & 217 Preamp. "Zorro" had a hand in some of the components on this model.

Overhead shots of the 217R.

220R FM Tuner Twins.

220R nudes. One of these FM tuners is an early version. The weight on the tuning shaft is a handful of thick washers. The later version has a nice BIG heavy aluminum barrel to smooth out the tuning of the earlier model. It does make a difference. Shielding added to the digital display board also.

Panama Red left his mark on one of the twins..... :)

I remember the original preamplifier planter box well. I was about 24 years old back then. Ken Cox and I were down at a tavern close to Spectro one day. We somehow ended up with a broken off part of a philodendren plant from the tavern. I took it back to our shop, but I did not have a cup to put water in so it would have a chance to grow roots. I  did have some preamp parts laying around since they weren't selling anyway. Thus, the original planter was created. A year later the company had moved 200 miles away to Pasco WA. I wanted to make a new planter box, but I really didn't like the silver face plates of the P202 amp and P101B preamp. I sent one of each out to have them black anodized thinking that this would make a better looking planter. Boy, was I ever right. When all the guys saw the planter boxes, we immediately changed the entire Spectro line over to black. Sansui was the only other black piece of stereo gear at that time. 1974 or so.
Here is a picture of Spectro Acoustics in Richland WA 1978. Bob and I have been hanging around for a long time now.

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Quote from: Robin on February 19, 2012, 02:30:11 AM
I remember the original preamplifier planter box well. I was about 24 years old back then. Ken Cox and I were down at a tavern close to Spectro one day. We somehow ended up with a broken off part of a philodendren plant from the tavern. I took it back to our shop, but I did not have a cup to put water in so it would have a chance to grow roots. I  did have some preamp parts laying around since they weren't selling anyway. Thus, the original planter was created. A year later the company had moved 200 miles away to Pasco WA. I wanted to make a new planter box, but I really didn't like the silver face plates of the P202 amp and P101B preamp. I sent one of each out to have them black anodized thinking that this would make a better looking planter. Boy, was I ever right. When all the guys saw the planter boxes, we immediately changed the entire Spectro line over to black. Sansui was the only other black piece of stereo gear at that time. 1974 or so.
Here is a picture of Spectro Acoustics in Richland WA 1978. Bob and I have been hanging around for a long time now.

Hey Robin, Thanks for the "story" behind the planter box! :) I assume you knew you needed a way to stand out from the big guns crowd and black face certainly did it!

My Spectro gear has some good  company. 5-6 Sansui 9090's, hey I'm greedy! A Marantz separates rack that looks great opposite the Spectro gear.

Not a big fan of the early white lettering. What's the story behind the Spectro Gold? When you went to the gold lettering it elevated the gear to a much higher level, softer and much classier look, at least in my opinion. The white was too harsh a contrast on the black. Now of course all the BPC "Black Plastic Crap" gear that followed has gold lettering. :(

It was 1977 I think. We were in the middle of a major cosmetic redesign. I broke my wrist so it was difficult to do the drafting. Remember this was before computers. Spectro was a pretty young company and were all pretty close knot. We would go out behind the shop at every break and play volleyball. One Sunday we all met at a park in Richland to play volleyball. Back then I was young enough that I could still drink, smoke and chase women. I remember diving for the ball after it had already bounced out of bounds. My wrist suffered, so boB drove me to the hospital to get it all betterized. The next three weeks were a @&%@ trying to do the drawings for this major redesign. I had boB's girlfriend do most of the actual drawing since I couldn't draw left handed. Part of this cosmetic redesign was to change the silkscreen color. We tried silver and gold. The gold was pure class. I vividly remember changing the white stripe on our EQ slider knobs to gold. This was a real pain. I think we used a thread dipped in Testers airplane paint. Spectro was the worlds largest manufacturer of graphic equalizers at that time and we had 50,000 white knobs to paint. Boy, those were the good old days.
I have a picture here that Bob kept. He is a wealth of old trivia stuff. This picture is of me at my wiring bench at Phase Linear in 1971. Bob Carver was my boss. Steve Johnston (founder of Trace Engineering) was my other boss. The photo doesn't show the bottle of Boones Farm wine that usually accompanied my wiring procedure. Two years ago I brought in one of my old Spectro Acoustics P217 preamps. It had a volume/on-off pot broken. These were made custom for us by CTS. I was hoping we would be able to cobble something together to allow it to function. 30 seconds later, boB reached into a box just outside of his office and pulled out one of the custom pots that we had used in the P-217 preamp 25 years before. Now why would he have the exact obsolete pot within reach that had absolutely no use to him whatsoever? He said, well you never know when something like this might come in handy. I no longer chastise him for keeping all that old junk around.


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Hello all! This has been a great history lesson to stumble across! I am a big fan of vintage audio gear, and have a modest collection. Learning first hand about what was going on behind the scenes is as interesting to me as, say finding some studio outtakes from your favorite musician. My electronic repair skills are slowing evolving, from "running a mean can of DeOxit and AirDuster" to replacing caps and upgrading cables and wiring. When it comes to design or troubleshooting, I am unfortunately clueless.

I particularly love the minimal aesthetic design of Spectro Acoustics stuff, I have a 217R that I am hoping to restore to it's original awesomeness, and one of my friends has a 217R in a wood case with a matching P202. I have question that I was hoping you might be able to help me with, albeit a longshot. I am trying to find a service manual for the 217R, if such a thing ever existed. Or, if you could tell me what I would need to do to get my phono section working again. The 217R still works great on all other inputs, I just don't get a whole lot of sound when trying to play records. So, I'm guessing it may need to be recapped on the phono stage, or there looks like there may be an IC chip on the board, and perhaps that needs replacing. I would be eternally grateful for any help you might could provide on this.

Your components are still highly regarded in the online realm of vintage collectors. I would love to restore this to it's original level, or even further, if any improvements might be possible through the wide variety of higher quality (or at least more expensive) components that are available today. I had even toyed with the idea of an external power supply, as that seems to be a common denominator in certain high end pieces these days. I've even seen some, Sutherland, for instance, that run on a bunch of D-Cell batteries. Just a thought... I'm not an engineer by any stretch, and these latter suggestions may be complete over-kill and ridiculous. I am a cabinet maker by trade, and provided I can get this baby up and running, I intend to build a Danish inspired light wood box to compliment it's exterior. Please know that this isn't a project I am working on to make a buck, I have been holding on to this preamp for 4yrs already, waiting for the right time and occasionally searching for info, and if I can get it working and possibly upgraded, it will be an heirloom piece, in the "never sell" stack along with my Luxman PD441. Thanks in advance for any help you may be able to provide.

I have thoroughly enjoyed this thread, and learning the backstory behind how this equipment came to be, and I am glad to hear that you are still providing people with a much needed quality product.

One last question... Whatever became of the 800watt car audio amp that you and your cubicle mate were working on?

Thanks! Jon B

JonB, I may have a service manual back at MidNite. I am in Hawaii at the moment, so e-mail me after the 15th and I will see. If not, the IC you need is a quad 4136 (if my memory still works). Don't mess with the power supply. It worked just fine. Battery supplies are serious overkill for people that just want to fiddle with things.
The phono stage is very simple. We used the original RIAA stage that Bob Carver designed for the Phase Linear 2000. Bob is a funny guy. He likes to dink with things for forever! Bob's original RIAA stage sounded great. Ken Cox and I got tired of waiting for the Phase preamp to get finished, so we built 23 of our own design just so we would have a preamp to use until Bob Carver stopped messing with the 2000. The Phase 2000 had 13 circuit boards, so Bob had lots of parts to fiddle with. Six months after we had built our own preamp, Bob Carver asked us what his original RIAA stage was. He could not remember, but he wanted to try it again. I do not know what ended up in the Phase preamp. I still have one of those original 23 preamps.

Ha! Bob liked to fiddle with things, I know how that goes. I am about 80% curiosity and 20% competency, I'm sure Bob's levels are a lot less disproportionate than mine. Thanks so much for the response and the insight on all of the things that were going on while this preamp was made. It's so rare to have any clue as to the back-story of any piece of audio gear, other than market conditions. I truly feel closer to this preamp already. Have a great time in Hawaii and safe travels back, and I'll email you after you get back.

Wow, this is a great thread. Is there some story to why it was called Trace engineering? Was  it derived from trace, as on a circuit board, or some other context?

In my early days of audio, 1971, at Phase Linear, Steve Johnston was Bob Carver's partner. Ken Cox ran the stores, and Greg Johnston wound transformers. In the mid 1980's Steve Johnston started Trace Engineering with his brother Greg, my old partner from Spectro Acoustics Ken Cox and Clyde Yamamoto. Clyde was a technician at Phase Linear. Mike Frost was another technician from Phase Linaer that was part of the original Trace crew. I heard that the name Trace came from Steve's mother.

Hello,

I worked for Spectro Acoustics just prior to their moving over to the west side of the state, and wow, in that short period of time I learned a lot. I was a teenager at the time, and this was my first electronics related job. It was really cool all the people who worked there, they were great to work with, and I remember the times as being some of the greatest of my life. I wonder where many of the people I worked with have ended up over the years. If you are out there, please drop me a note, as I would like to hear from you. I believe I still have hanging up, a black "T"-shirt with the Spectro Acoustics logo on it from my employment.

I can remember the quality of the products that were being produced as being top notch. You were encouraged to do your job to the highest standards - this was the first place, and the only place, that I have worked where you signed off on your work, inside the product. It was all there for everyone to see, your initials. If you were one of the people who had worked there for a while, you were given the opportunity to get a "name", such as "spiderman".

I still own the Spectro Acoustics 200SR power amplifier I purchased while employed with Spectro. I have replaced the LEDs on the front, and the filter caps. But that is pretty much it. It still is working perfectly. I can remember my dad was upset that I purchased the amplifier, but I am not sorry that I purchased it. I have since added two pre-amps, two equalizers, and one FM tuner to the collection. While employed, the FM tuner was one of my favorite pieces of equipment to do assembly work on.

The great people at Spectro taught me the importance of teamwork, craftsmanship, and pride in a job well done.

Also, I can remember the president of the company coming up to me and telling me that anytime I wanted, I could stop by his office and talk to him. Whatever was on my mind. How many companies will let you do that today? Wow.

Hey, is this Phil? I think Spiderman was Phil? Your wife worked at Spectro too if this is Phil.
I still go to lunch with Ken Cox once in a while. Bobby works here at MidNite. I think there is a history of the Northwest inverter companies at Sierra Solar. Go to their website and see if you can find it. There will be a picture of the Richland crew on it.
Let me know if I guessed correctly?

Robin,

No, this is Brian Dierks. I vaguely remember Phil, I think. I was with Spectro in Richland in 1979. I worked parts stuffing, power amp assembly, tuner assembly, and also made wire assemblies and other sub-assemblies. I usually was stationed on a bench, I believe a row off of the parts stuffing stations. I did not make the move to the west side, and who knows where I would be now if I had. If memory serves me correctly, Lyle was my supervisor. I believe one of the girls that worked assembly was doing assembly work here in the Tri-Cities a while back. I was working next door, to an electronics fabrication facility. That was 20 years ago. Wow, time flies.

Brian, were you part of the crowd that went out behind the shop at break and lunch time to play vollyball?
Boy, we sure did a lot of stuff tgether back then. Baseball, beer, chasing girls......oh those were the days.

Hey Guys! I found this thread and forum through Google. I am the proud owner of a
217R Preamp Serial #0330
210R EQ Serial #0600
200R Power Amp Serial #0212

I still use this system to this day with 2x Kef 104aB Speakers. Actually looking for new speakers for her! Any info about SA you can provide would be awesome.

Thanks!

Hey  SpectroAcousticsFan  !!

Good to see you here !

If you read some of Robin's posts, he talks some about our time way back in the 1970s at SA.

I was there too.  We have a 210 EQ hooked up to our paging system here at MidNite Solar.

Hopefully I can post some pictures from back then here on the web site too.

boB

Here are a few pictures of the good old days when Bob and I were young enough to smoke, drink and chase women.
More on the next post

Bob in the late 70's
Bob was our chief engineer at Spectro. We were just kids back then. We didn't make a lot of money, but we knew how to design cool stuff and have fun at it. Kind of like now?

Here is a link to the history of the Northwest inverter companies. I noticed it hard to find elsewhere, so I updated it a bit and put it on the MidNite Website.
http://midnitesolar.com/pages/nwHistory/history.php

Bob mentioned the 210R on our paging system. We also have a 217R and a one of a kind Spectro amp.
I have as full rack of Spectro stuff in my office. One of these days I gotta hook it up.

OK, now for another dumb Robin at Spectro story......
Back then (1978) I was into black powder guns. We went to the Columbia river with a hunk of Styrofoam and an old style preamplifier. We would float the preamp on the river and try to hit it with my 45 caliber Kentucky rifle. I don't think we were ever able to sink it.
I also had a 69 caliber flint lock pistol. This is a really big gun! I had never fired it, but was showing it off after hours to a couple of constyruction workers that were working on our building. One of the guys wanted to fire it. I didn't have my powder measuring tool with me, but I had everything else, so I did load it up. This construction worker was an annoying sort of guy and partially because of that and partially because we were all pretty liquered up, I put lots of powder in it. I am guessing about 150 grams. The normal load should have been 50. I did not have a flint, so as he was holding the gun (pointed at a stanless steel sink out behind the circuit board shop next door), I was touching matches to the flash pan. Three matches were lit and three went out. The construction worker said "your turn". Oh crap!!!

I had not expected this, and I knew the gun was going to kick like a mule. Well it turns out that between the beer and the need to not look chicken, I agreed to hold the gun and have him light the match. I was holding the pistol with both hands as hard as I could. Once again three matches were lit and then went out without ever lighting the powder in the flash pan. I was relieved because it was his turn again. He said, just one more. Crap. this one lit! The gun flew out of my hands and landed about 20 feet behind me. The ram rod pulled out of the gun and landed 20 feet behind the gun. A welt the size of a golf ball quickly developed on my hand and required an immediate trip to the emergency room. Two things happened from this episode. I received a bill the next day for a hole in the sink from the circuit board company. (1" hole front and back) and I built a case to display my broken gun in. The stock was cracked in 7 places. I still have this gun today, but it has never been fired since that day.

One more quick story. Earlier in this thread I mentioned the broken wrist episode. Well Bob's girlfriend and I were able to get all the gear redesigned cosmetically. We took it all to CES in Chicago. Now, normally we would sell only a couple thousand dollars of gear at a show. dealers want to window shop, not purchase. The year we brought the new redesigned stuff we sold $300,000.00. Our cool brochures were part of the success there too. I will photograph and put some of them here. They were the best in the industry at the time.
The picture may have been from that CES show.

Robin, Looks like you have one of those MXR yoyos in your hand at the CES booth item you are looking at.

boB

I think I still have that yoyo somewhere? Those yoyo's were everywhere that year. Our friendly competitor, MXR gave them out. I believe they still owe me $23.00 for a bar bill they stiffed me for at that show.

What Fun!  Thanks for adding some detail to the SA story.

Never did own any SA stuff,  the first stereo I had was an AR Amp and speakers and a Dual TT.   The SA revolution came a bit later.

Still do have a Carver receiver that dates from about 1980 -- works fine.  Thanks again,  hope t see more.  Vic

Quote from: Robin on February 22, 2012, 02:24:33 AM
It was 1977 I think. We were in the middle of a major cosmetic redesign. I broke my wrist so it was difficult to do the drafting. Remember this was before computers. Spectro was a pretty young company and were all pretty close knot. We would go out behind the shop at every break and play volleyball. One Sunday we all met at a park in Richland to play volleyball. Back then I was young enough that I could still drink, smoke and chase women. I remember diving for the ball after it had already bounced out of bounds. My wrist suffered, so boB drove me to the hospital to get it all betterized. The next three weeks were a @&%@ trying to do the drawings for this major redesign. I had boB's girlfriend do most of the actual drawing since I couldn't draw left handed. Part of this cosmetic redesign was to change the silkscreen color. We tried silver and gold. The gold was pure class. I vividly remember changing the white stripe on our EQ slider knobs to gold. This was a real pain. I think we used a thread dipped in Testers airplane paint. Spectro was the worlds largest manufacturer of graphic equalizers at that time and we had 50,000 white knobs to paint. Boy, those were the good old days.

Only 50,000 knobs to repaint? OK Robin, you opened the door......:)

Looks like there are still more of those darned knobs that need painting.

Looking for advice on repair of a Spectro Acoustics 202. Just took this amp out of two year storage and the left channel output is about half of the right. I'm not sure of the function of the two trim pots, but both, especially the left, have deteriorated badly. The blue insulation of the left pot literally disintegrated as I was attempting to adjust it. Right was not much better. Are these actually gain controls? Or something else? Probably I could replace them if appropriate.

Opinions sought and appreciated.

Ut oh, those are bias adjustments. We adjust the bias current for lowest distortion. Put them back to where they were if you can remember.
Maybe Bob can answer the question about lower output?
Did you swap the input cables to make sure it is the amplifier and not the preamp?
By the way, I just bought a Spectro 200SR on E-Bay. We will be modifying it to use on development of our micro inverters. We need a good 120VAC source that can also sink current back into it. Don't know if we can just use a transformer to step up voltage or actually modify the amp for higher voltage?
I think we use3d a Crown amp at Outback for this same testing.

Quote from: wanders on November 23, 2012, 12:26:49 PM
Looking for advice on repair of a Spectro Acoustics 202. Just took this amp out of two year storage and the left channel output is about half of the right. I'm not sure of the function of the two trim pots, but both, especially the left, have deteriorated badly. The blue insulation of the left pot literally disintegrated as I was attempting to adjust it. Right was not much better. Are these actually gain controls? Or something else? Probably I could replace them if appropriate.

Opinions sought and appreciated.

Yeah, that would be a bias trimmer.  If that trim-pot goes open, that channel can get excessively hot.  In that case,
until another trimmer replaces it, I would short it out.  That will bring up the crossover distortion some but you may
not even notice it.  Those trim-pots are 100 Ohms.  R35 and is paralleled by another resistor to help out in case
it does go open, but still may get kind of hot if it does disintegrate. 

I'm not sure about the volume level of the one channel being lower.  What happens when you swap the left and
right channel inputs ?  Does that same channel stay lower in volume ?

Or maybe that one channel is actually clipping earlier than the good channel ??

boB

PS, here is a schematic of the basic Spectro 202 amplifier module...
R35 is kind of in the middle and to the left a little bit.

http://k7iq.midnitesolar.com/Spectro-202-scamp-BW.gif

Thanks for the advice & especially the schematic. Issue is the amp, not the pre, etc. Right trimpot shows a range of 0 to 24 ohms; left channel pot is faulty. Found a temporary 25 ohm pot at r/s, but, of course, that didn't affect the basic issue; if I can find the problem I'll get a proper replacement for the bias pots. I'll work with the schematic and see what I can do. I'll post results down the line.

Thx

You may need to get a hold of an oscilloscope and audio generator. IT is pretty easy to follow the schematic and trace the signal on both channels to see where one drops off. Getting the equipment is another matter. You might even luck out and find some cheap stuff on E-Bay?

Quote from: Robin on November 24, 2012, 12:58:05 PM
You may need to get a hold of an oscilloscope and audio generator. IT is pretty easy to follow the schematic and trace the signal on both channels to see where one drops off. Getting the equipment is another matter. You might even luck out and find some cheap stuff on E-Bay?

I have access to an oscilloscope and been interested in getting in to that. Thanks for the advice. If I can get this thing fixed, I'll post the results.

If the main problem is low gain, it ~may~ be that the input op-amp is not working.  It gives the amp a gain
of about 3 or so.  If the zener diodes that supply that op-amp are shorted, then maybe it is just bypassing
the op amp or maybe the op amp itself is dead.  I think it is just a single 741 type pin-out.

The earlier amp modules did not have that op amp.  Instead, the feedback of the amp module
was just set higher...  In fact, as I remember, R15 was 27K Ohms instead of 8.2 K Ohms in
the schematic.  If the problem IS the op amp circuit, you could bypass the op-amp gain
circuit and just change R15 back to 27K and get that gain back.

boB

boB,

Thanks for that suggestion. My amp does not contain an op amp and, as you suggest, R-25 is 27K. The information, however, caused me to look more closely in that area and I found that C-18 (little hard to read the schematic there) is spec-ed at 10 uf. On the good pcb, the component reads 12 uf (out of the circuit), however, on the low output board, the cap reads 33 nf. In your view, would that be sufficient to cause the output loss?

Thanks,

Quote from: wanders on November 25, 2012, 01:23:40 PM
boB,

Thanks for that suggestion. My amp does not contain an op amp and, as you suggest, R-25 is 27K. The information, however, caused me to look more closely in that area and I found that C-18 (little hard to read the schematic there) is spec-ed at 10 uf. On the good pcb, the component reads 12 uf (out of the circuit), however, on the low output board, the cap reads 33 nf. In your view, would that be sufficient to cause the output loss?

Thanks,

Yes, the low capacitor will definitely cause that problem.  Great detective work!

Thanks, I'll replace that part and post the results.

boB, Robin,

The replacement cap fixed the problem. For good measure, I replaced the rest of the electrolytic caps on both boards. I'm listening now and, even with all new caps, the amp sounds better than I remember. As noted, I benched this amp a few years ago in favor of a better sounding Hafler P3000. Think I'll give the Spectro another shot at the starting rotation.

Thanks for the help.

Warren

I would like to know what the connection was between Impulse Audio and Spectro Acoustics. When I was considering purchasing a Spectro Acoustics P-101 in 1975, I was given marketing material that had Impulse Audio written on it. I was told it was the same people. The items appear very similar. I do have the material scanned as a pdf file, but don't know how to upload it here.
Was the Canadian dealer who said he could sell the pre-amps Jan of Jan Stereo West from Vancouver, BC? I purchased my Spectro Acoustics P-101 from one of the franchise stores. It is a silver face with a SN of 74008. Thanks for your time. Doug

Jan Rybar was a mover and shaker in the HiFi industry in Vancouver. He was one of the first to sell the Spectro line. Before we built Spectro, we built the Impuls Audio preamps.
Here is the real story. Ken Cox and I (future president of Trace Engineering), built 23 stereo preamplifiers while working at Phase Linear. Some of the emplyees and us, wanted a preamp to go with our Phase Linear power amps. Bob Carver was taking his time in messing with the Phase 2000 preamp. We just got tired of waiting for him and decided to make a few much more simple preamps for the interum. Bob Carver even bought one.
A Canadian salesman came down to Phase for a visit one day to see how the progress was coming on the Phase preamp. The Phase preamp wasn't ready, but he saw one of our little preamps. I think it may have been called the Rob-Ken pre-amp? He said he could sell a bunch of them. That statement launched Spectro Acoustics. Ken and I decided to build preamplifiers, but something a bit better than our 23 simple designs. The Impulse Audio preamp was born. I doubt that we ever made more than a few hundred of them before switching to Brian Morreson's designs of the Spectro Acoustics gear. The Impulse Audio was my design, and I am not much of an electrical designer. They didn't sound bad though.

So interesting hearing all of this history right from the guys that designed and built these products. I have had Spectro stuff since the very beginning. I had a 217 a 200 series amp and a 210R. I kept the 217, and now I just picked up a second one (my favorite sounding preamp of all time). I also have three versions of the 210 now.

I just picked up a very tired 202 amplifier with the midnight blue logo graphics on the faceplate. I decided to recap everything and upgrade the connectors etc. I stumbled on what look to be four three leg transistors? The are attached to what i am guessing are small heat sinks (two on each driver board). The parts are so old now that only one of them had any visible markings on them. I have tried to find anything that resembles the part numbers and no luck. I was hoping that possibly someone here would know what these are and what would be a suitable replacement for them?

Thanks in advance.

That is indeed a very early unit. We switched to different driver transistors and power transistors later on. The replacement drivers would be 2N6474 and 2N6476. The power transistors switched to Motorola MJ15024.
All of those are still available.
Good luck with your amp. We were just dumb kids back when we built that stuff. We really didn't understand how good and simplistic the gear was.

Robin. Thanks so much for this information. Greatly appreciated. Is there much difference between the 2N6474 and the 2N6476?

I think what you did back then was pretty impressive. The products were superb, and they brought great hi fi to people at an affordable cost. I still remember the quote from Len Feldman that was included in the 217 brochure "The little unit tends to dispel the myth that a really superior separate control unit preamplifier has to cost a small fortune".

Someone had to design the electronics circuits, parts had to be sourced and purchased, metal fabricating and artwork, logos, names, distribution, marketing. This is a huge undertaking to produce something like that, and at that level of built quality. The preamps and the EQ's are still going strong today. The Alps pots in the 217 are top notch. My 202 amp was worked on by a guy called "Little Diablo" He left his sticker on the power transformer.

Thanks again for the help Robin.

Hello Ingot !

FYI, here is the schematic for the amp module.
The original module did not have the op-amp in the input
and had a 27K Ohm feedback resistor rather than the 8.2K.

http://fusion.midnitesolar.com/spec202a.gif

and the LED circuit for the 200SR...

http://fusion.midnitesolar.com/200SR-LED-circuit2.gif

The 2N6474 and 2N6476 were NPN and PNP complimentary pairs for the drivers.

boB

Yes, we did design circuits and products, buy parts, stuff boards, test units and all that. But remember boB and I were still pretty young back then. All that work tended to get in the way of drinking beer and chasing skirts. Now we are too old to have that kind of fun anymore so we just work.

Quote from: boB on February 22, 2013, 08:57:18 PM
Hello Ingot !

FYI, here is the schematic for the amp module.
The original module did not have the op-amp in the input
and had a 27K Ohm feedback resistor rather than the 8.2K.

http://fusion.midnitesolar.com/spec202a.gif

and the LED circuit for the 200SR...

boB....thanks so much for that information. I will post some pictures of the amplifier when i finish everything. My first Spectro amp had an all mesh cover on it. This 202 is thin anodized aluminum with a few vent slots near the output transistors.

http://fusion.midnitesolar.com/200SR-LED-circuit2.gif

The 2N6474 and 2N6476 were NPN and PNP complimentary pairs for the drivers.

boB

Quote from: Robin on February 22, 2013, 10:00:59 PM
Yes, we did design circuits and products, buy parts, stuff boards, test units and all that. But remember boB and I were still pretty young back then. All that work tended to get in the way of drinking beer and chasing skirts. Now we are too ld to have that kind of fun anymore so we just work.

You guys are pretty modest. never too old to chase skirts....but harder to catch now. 

The Spectro stuff will have a lasting legacy. The 217 is really an inventive design with the cartridge loading section. The sonics are as good or better than the best available today. And it's built like a tank without looking like a tank. It's like the "MiniMoog" of preamps.

After completely gutting my 202, I decided to replace everything except the power transformer. The way this thing was designed is beautiful. A lot of fun to work on.  I decided to recap my 217's  and then I looked at trying out new op amps that weren't available back in the day. I love the sound of the 217, but I have ordered some new ones to try. Then I noticed that the faceplate is separate from the base chassis. That means rack or non rack, and make your own. Like the 202, the 217 is all right there. nothing hidden, even the pC mount rca connectors can be replaced easily. It disassembles easily. No doubt designed to assemble just as easily. I spent a couple of hours designing a new front panel. (not finished yet). I will do the same for the 202 so that they both look like cousins. (which they are). The 217 that I have in my office ( I spend a lot of time there) is running into two Rane ME30 graphs ..into a Hafler DH220 and then into a pair of EAW JF80's.. For me it's a magic combination. The 217 is a huge component of the sound, so it will be interesting to find out how more modern rev op amps factor into it. Quite possibly I will end up keeping the original 4136PC.

My Gold 217

Ingot, I LOVE that new screen job !  Looks nicer than the original !

boB

boB, Thanks for the comment. I wasn't sure if this would be sacrilege or not. I'm waiting for some parts for the 202 and I'll post some pic's of it when I'm finished (hopefully there won't be any smoke).  I'm using new 18000 uf caps and i installed a higher rating bridge rectifier. Is it necessary to use a variac when I first plug it in? or does this only matter with tube amps?

Quote from: Ingot worx on March 09, 2013, 05:08:16 PM
boB, Thanks for the comment. I wasn't sure if this would be sacrilege or not. I'm waiting for some parts for the 202 and I'll post some pic's of it when I'm finished (hopefully there won't be any smoke).  I'm using new 18000 uf caps and i installed a higher rating bridge rectifier. Is it necessary to use a variac when I first plug it in? or does this only matter with tube amps?

Variacs are handy for these types of things either way, but, I think that if you have a fuse in there, that should be enough.

The larger caps ~may~ have more of a tendency to blow with the greater turn on surge though.  For that reason alone,
it might not be a bad idea to use the variac I suppose.

boB

the caps themselves or the fuses? i was into using a bit more capacity in an old lafayette receiver/amplifier to try an ease the pumping effect from the power supply when one channel draws heavily causing a bit of thd in it due to the common supply. i didn't get too far with it though and lacked the equipment to see the results of my efforts. ideally, separate supplies should be used to eliminate this pumping of the supply and thd you don't need. it was a quad amp setup (remember those?)

anyway, if there is a problem with the cap values you have chosen you can either go closer to the original design caps or place a tad of resistance inline to the caps to act as a bit of a limiter.

Quote from: niel on March 12, 2013, 05:11:42 AM
the caps themselves or the fuses? i was into using a bit more capacity in an old lafayette receiver/amplifier to try an ease the pumping effect from the power supply when one channel draws heavily causing a bit of thd in it due to the common supply. i didn't get too far with it though and lacked the equipment to see the results of my efforts. ideally, separate supplies should be used to eliminate this pumping of the supply and thd you don't need. it was a quad amp setup (remember those?)

anyway, if there is a problem with the cap values you have chosen you can either go closer to the original design caps or place a tad of resistance inline to the caps to act as a bit of a limiter.

I meant the fuses might blow because of the surge that charges up the caps.

boB, thanks for the advice. I will use the variac when I get ready to fire it up (someone also mentioned using some light bulbs in series as an alternative).

here's where I'm headed with the look of the 202. It has such a forward thinking design already with the clever backlit midnight blue logo. That was really well done back when LED's were almost unheard of. When that thing is on it really looks appealing.

I'm just tweaking what already exists (you guys did the heavy lifting and invented the concept). I am just going to do a simple overlay on a new faceplate with some tempered glass or plexi and FX lighting gel behind to get the color (I'm going with a gold for now, but I like the blue a lot too. I won't use through bolts to fasten it all, just some hot melt glue for the covers behind the faceplate. The grey overlay to trim out the whole thing could be anodized aluminum or powder coated steel (very thin), or you could do a 3D print of something with 3d contours.

the 202

Looks like the long overdue facelift on my 500-SR is getting moved up.... :) Condition pictured is how I received it about 10 years ago. It saw a lot of road miles by the previous owner. Small band going from town to town and not much care in how it was handled. Electrically it has held up fine to all the abuse.

Quote from: onanparts on March 13, 2013, 11:41:19 AM
Looks like the long overdue facelift on my 500-SR is getting moved up.... :) Condition pictured is how I received it about 10 years ago. It saw a lot of road miles by the previous owner. Small band going from town to town and not much care in how it was handled. Electrically it has held up fine to all the abuse.

Wow! I remember  seeing that model in night club AV racks in the 80's. Always looked really impressive with 8  or so of those things all racked with the LED's all reading in tandem. That was the BGW era.. Crest was there too. I remember the guy that sold me my Spectro amp (it was a plain faced rack mount 200 series) He referred to it as " poor man's Bugwa (BGW).  What I realized about the 202 that I am rebuilding is that the amp channels can be removed with just a couple of screws and then "pop" just disconnect the whole channel from the Molex connector. So "modular design"  this would have been advantageous in touring situations / live situations where a backstage tech could quickly swap out a channel during a show. Designed for high duty cycles and physical abuse. These things really set the standard for what was required in the pro audio industry which was evolving quickly with greater demands and SPL requirements being asked for.

The fact that these amps are still ticking is a testament to their build quality and design. Other than failing caps and some semiconductors that are getting tired, the core of the amp could conceivably last forever.

I have finished re capping my 202. I also replaced the RCA connectors and the bridge rectifier. I kept the original RCA output transistors because they all work fine, but I also replaced the.33Ohm 2 watt resistors with film resistors. I tried to use good electrolytics like Panasonic where I could find them, and polypropylene wherever possible. All of the driver transistors were OK, but I picked up some spares. having the schematic really helped..Thanks much for that! The Power caps were replaced with 1800uf caps, and I had to drill out new mounting holes for the housings. All in all, I'm very happy with the sound of the amplfier. It's really crisp and nuanced. I'm going to experiment with some of the cap changes from new to older versions from the schematic, but I really intend to make some new looking faceplates for it and the 217.

Hello all,

I've been enjoying catching up on some of the Spectro history while researching my latest find. I recently purchased a rack that included the following:

Kenwood KD-2055 turntable
Denon dvd player (forgot the model number)
SA 500SR amp
SA 217R preamp
SA 210R eq
SA 220R fm tuner
KLH DNF1201A dynamic noise filter
KLH TNE7000A transient noise eliminator
KLH Model-1 speakers w analog  bass computer

The left channel was a bit scratchy when testing the setup so I figured all it'd need is a good cleaning. The 500sr amp ended up blowing the speaker fuses, main fuse and blew a test speaker. Afterwards the left channel was obviously completely out, no leds worked. I thought it could be some blown transistors so I had it taken in to a local shop and the guy replaced the problematic transistors. There is still some fuzziness/scratchiness in the left channel (the problematic channel). I've used different speakers and the problem persists. Is this an indication of more transistor troubles, are others failing? I must admit I don't know much about repairing these devices. I've been looking around as much as possible to identify the problems so I don't get taken advantage of with further repairs. I'm also interested in potentially working on this myself.

Any suggestions would be a huge help. Also if anyone has any paperwork or diagrams on any of these pieces that would great. I did manage to get the manuals for all these units which I plan on scanning and uploading for all later this weekend. I'll also upload pictures of the setup later.

Thanks for the stories and input!

Bob probably has the schematic for the 500. If he has it, I will ask him to post it. The noise may be filter caps. One amplifier channel may just be better at hiding it than the other channel?

Boy are we ever in luck! I found something right above my desk. I spent an hour or so and turned all this good stuff into a pdf, but it is 5 megs, so Bob will post a link to where to get it. What I found is not only schematics, but parts lists, circuit description and test procedure. For a bunch of 20 something year olds that spent way too much time at the bar, we actually did some good work back then. I also found a schematic for the 200 SR. There is a hand written test procedure for the tuner, but nothing else?
Hope this helps.
Robin

Thanks for the quick reply. Man, that would be great to get my hands on those. Hopefully they'll help shed some light on the matter. I'm taking the unit back to the tech on Monday as I have some warranty on the repair. I'll run some of this by him. I'll certainly keep my eyes peeled for the location of the PDF from Bob.

Well I'm a 20 something year old that probably spends too much time at the bar and listening/fiddling with this gear. It is really some amazing stuff and I can't wait to get it sorted out. I've been looking all over to get as much info on the Spectro Acoustics line as possible. Thanks again for the feedback. Pictures and scans are still on their way, crazy work schedule as of now!

OK, Bob hasn't placed a link to the document yet and I don't know how to do large documents, so e-mail me for Spectro Acoustics 500 watt amp documentation. I also have a 200SR schematic.
robin@midnitesolar.com

Here it is !

http://k7iq.midnitesolar.com/spectro%20500%20test.pdf

boB

Thanks for throwing that link up, Bob! The schematics definitely came in handy for the tech. However, not handy enough apparently. Just got the amp back and still distortion in the left channel. This time he said he found more transistors that looked to be on their last leg, some resistors, and he adjusted the bias. I'll suggest the filter caps when I take it back tomorrow. Any other suggestions before I take it back tomorrow? The distortion seems to occur during dialogue or segments of low volume. Thanks again for any suggestions.

Transistors do not typically have a last leg. They let you know they are unhappy by blowing up. I would be very suspect of filter caps. There certainly can be other things causing the distortion, but it probably is not a power transistor. Might be smaller ones or leaky capacitors?
If worse comes to worse, maybe we can have bob look at it. Bob is very busy here though and may not have enough time although he would really enjoy it.
I would like to find a Spectro 500 for sale someday. We might use it here at the plant.

Just got the amp back and the tech said the bias was off. I hooked the amp back up and finally the distortion was gone and everything sounded great. I ran the thing for about 30 mins before the amp popped, killing the left channel and frying my good speaker. The left grill on the back of the amp couldn't be touched it was so hot. Obviously I'm getting very discouraged with this whole thing. Im beginning to think taking it back to the same tech would be useless.

The tech turned the bias up too far!!!

random question does anyone know where i could find a replacement fuse holder mine fell out of my 500sr when i was bringing it home.

havent had anyluck at all finding one :S

my 500sr was paird with a nad but i sold that today and think im gunna run it paird with a dynaco pas3 tube pre witch sounds :) and way nicer then a st70 oddly

We used very standard panel mount fuse holders. I would try E-Bay or some of the online electronics stores. Heck, Radio Shack may even have them?

has a lip on the cap that extrudes into the holder and the metal part of the cap is longer then any fuse holder i have ever seen ive gone through all my 40 yr old computers and such hoping to find one even looked at new stuff none of them seem to match thought i would ask
also tried local repair shops none of them have or seen one quite like it
(http://imageshack.com/a/img835/5572/6upw9.jpg)

just noticed the low searial  m0028 could be meaningless but could be neat history i have no idea
(https://imagizer.imageshack.us/v2/800x532q90/835/ow1fv.jpg)

The 500SR used 3AG fuses. Very common. You can replace these fuse holders with any panel mount fuse holder meant for 3AG style fuses.
The 0028 serial number means it was the twenty eight one built. Pretty low serial number.
Nice amplifier.

This is for boB, Robin or any other Spectro Acoustics team members.

I love old tube and solid state gear (grew up w/tubes and ham radio) and am now rebuilding the SA 202 power amp.  Nice vintage piece without much damage so far.  I've read every post I can find, and thanks to you guys I got the schematic.  However, the 202 has a clipping meter whose circuit I cannot find.  I think I can guess how it works, but it would be nice to get the schematic for this little circuit.  Any help would be appreciated.

Jim aka Sardobang

I do not think we have a schematic of the clipping indicator circuit. It was very simple though. It has a neon light and a transistor or two. If it doesn't work, try replacing those parts. The transistor was nothing special and part numbers should be on the parts. I believe the parts are on a circuit board right next to the neon lights. Do the clipping indicators have a plastic back to direct the light forward?
We contacted a major plastics supplier in Seattle early into production on the P202. We needed some thermal form type of plastic to continue production of the light shields. The plastics salesman asked us what type of thermal forming machine we were using. We weren't quite ready for this question, but we answered him truthfully and waited for the laughter. We told him we were using a toy machine made by Mattell! To our surprise he said that the toy machine was actually quite good. We used that toy machine for years until the P-202 turned into the 200SR and we no longer required Clipping indicators.

I don't know what the circuit was behind the front panel but on the scamp module schematic,
Q3 is the clipping sensor in the upper right corner.

I think the "toy" was called a Vacu-Form ?

aww fooy the 500sr right channel just faded all the sudenl to realy quiet guesing recap time?
got any electrical drawings and recomendations on what i should be using for replacement caps?

Quote from: 1ajs on June 04, 2014, 04:08:00 AM
aww fooy the 500sr right channel just faded all the sudenl to realy quiet guesing recap time?
got any electrical drawings and recomendations on what i should be using for replacement caps?

Did you try smacking it ?

If the caps somehow go away (stop being good capacitors), the rail voltages should be different plus and minus voltages.
I think the voltage was something like +- 80 volts ?

Might be a bad connection somewhere or a bad volume pot if the audio just kind of faded down behind your very ears.

after pulling out the 2 moduals and cleaning and checking them over its all working in fine order now. and the mild hum i was having is completely gone. really enjoying the design of the 500sr and doesnt run stupid hot like the dynaco qsa300 i used to have.. witch is nice for summer use. sept in the winter i want the heat o -40 winters

counted 5 stamped names so far
ZORRO & DJ also found some of the boards were not stamped by anyone or signed as far as i could tell

thanks for your opinion
and the history of the company :)
also just noticed the link to the schematics for the 500r sr stuff sweet wish i had earlyer.
txs again

My 500SR finally made it to the bench.. :) First up is a very good cleaning!

Found a few names had not seen before. Tinker Bell & Short Cakes.  :)

And forgot about an old ad I had for it.

Was going to replace the 100K Ohm level pots but the ones I got do not have enough thread length.  :(

Short Cakes was a short cute blond lady names Suzie. She was bob's girl friend back then. Tinker Bell was a cute little red head. I rented a 23 foot camping trailer from her dad and lived in it.
For some reason we had a lot of very cute girls at Spectro?
Those Spectro transistors are actually MJ15024 transistors.
The 500SR is by far my favorite amplifier. I wish I had one!
The lights were very well done.

Quote from: Robin on June 18, 2014, 01:01:31 AM
Short Cakes was a short cute blond lady names Suzie. She was bob's girl friend back then. Tinker Bell was a cute little red head. I rented a 23 foot camping trailer from her dad and lived in it.
For some reason we had a lot of very cute girls at Spectro?
Those Spectro transistors are actually MJ15024 transistors.
The 500SR is by far my favorite amplifier. I wish I had one!
The lights were very well done.

Who was in charge of hiring those "cute girls" ?  ;D


Since you mentioned the transistors....

The specs in the manual, FTC etc. are all at 8 ohms. But under output capabilities minimum recommended load is shown as 4 ohms.
I know the protection circuit should kick in at loads less than 2 ohms but this is my question:

Why no specs at 4 ohms? Higher THD numbers? The 70's were all about watt wars and THD etc. The only speakers I have that are rated to handle the 500's max output are 4 ohm JBL's.

Note: My ears can't hear the difference between .005% THD and .25 THD etc.  :)

Just wondering.... ;D

FTC ratings were to be done into 8 ohms. I do not know why we didn't also rate them into 4 ohms. The amplifiers work just fine into 4 ohms. Lots more power too.

  Hello, I am new to this forum. I hope I have posted in the correct place, please forgive me if I've done wrong.
  I recently purchased a Spectro Acoustics Model 202 amplifier and preamp at a local thrift shop for just $20. I was very excited as I love old amps from this era. My wife was probably not as excited as me. I just tell her that they all do something different so I need them all.
  Upon hooking the pair up I discovered that one side of the preamp is not working. I put it aside and used another preamp I've got for the time being. The amp sounded fantastic, probably the best I've ever heard, up until Friday evening when it shut down. I investigated the fuses and it seems that the one nearest to the bottom has blown. Please, bOB and or Robin, please help if you have time, as I really love this amp. I am using one of my old favourite amps for now, a crown d150a, and I miss the Spectro already !! I am posting from Vancouver, BC, Canada and had never heard of Spectro Acoustics until I found these two gems. I've read up on the history, cool stuff! Now I wish this cool amp would run again. Please help if you have time, thanks in advance.
Best Regards,
J

Jim , If you get a response & need a go between , I live in WA & BC and travel monthly . I can only help if no money/ value  is exchange !!
FREE !


I'm just putting it out there , if I may help .

VT

Sorry to hear that fuse blew !  It may mean that the output transistors are bad OR it might just
be a bad fuse.   The schematic for the 202's amplifier module can be found here...

http://k7iq.midnitesolar.com/Spectro-202-scamp-BW.gif

You might take an Ohm meter and compare against the two channels and see if you
can find that the output is shorted or whatever, or, find another 5 amp fuse and
put it in and see if it blows again.  If it doesn't blow, check the output for DC coming out.
Shouldn't be more than around 0.1 volts DC or so with nothing connected.  Make sure
there is no speaker connected when turning it back on though.

If you are uncomfortable doing this, then I can take a look at the module and see if it
is broken or not.

Also, some of the 75 volt filter capacitors would go bad on those amps after a while.
Sometimes it was just the connection on the cap.  You should measure around + and -
68 volts DC with respect to the middle (ground/minus) with good caps.

boB

CDN-VT: thank you, I may take you up on that offer !!

boB: thanks for the quick reply, I will try my best to follow your instructions. If I can't get it I will get the amp to you when it's convenient for you. I would like to post some pictures here but I'm having troubles, they are too large, i will find a way so everyone can see the 202 amp and the 101B preamp I've acquired. Love them !! I've got pictures of the insides as well, is there a way to get them to you if I can't post them here ?
Thanks again
J

if you area using Microsoft picture viewer there is an option ubder VIEW I bekeive to resize the pictures, be sure to do this operation on a COPY of the original and then you will be able to post them...

Yesterday Robin was kind enough to let me scan some of the Spectro Acoustics history from his archives. Thanks again Robin!  :)

Pictured here is very early sales literature from near the beginning. I forgot to ask Robin if he remembered what year? 1973, 74, 75?

SDR2 was a partner back then and it states: Manufactured for Spectro by Rob-Ken Audio Products.

From post #5 by Robin in this thread.

When Ken and I started Spectro, one of our first products was the RobKen 2123. The model number came from our ages.

So here it is, most likely the earliest printed literature available on Spectro.  :)

Now for the first time ever seen....as far as I know by anyone outside of Spectro Acoustics.

THE ROCK! The 600R Prototype Spectro Amp that unfortunately never saw the light of day until now.  :o

This was going to be the 500R's big brother. Massive heat sinks! It was very close to being completed when Robin and boB moved onto other projects. Maybe someday boB will have the time to bring this beast to life, but Midnite has his undivided attention with their numerous projects so it may be awhile, if ever. But I will try twisting his arm now and then about it.  :)

The rear view. The WARNING is a nice touch.  :)

Quote from: onanparts on January 17, 2015, 04:04:17 PM
The rear view. The WARNING is a nice touch.  :)

Yeah, much more classy that "No User Serviceable Parts Inside" ;D

It was great having you out here yesterday.

I would LOVE to see one of those heatsinks on an MPPT charge controller !

boB

We did have a good day Friday with Onanparts. He got a full days worth of MidNite and Spectro earfuls. We started Spectro in 1973 by the way.
I really would like to see the ROCK play music some day. Bob isn't too far off with his statement of massive heatsinks on a charge controller. We are working on that now.

Enjoyed looking through the Spectro archives and of course being exposed up close and personal to see products not just "assembled" but actually "designed" and "manufactured" right here in the good old U.S of A. !  :)

Speaking of Spectro archives....here are some more goodies.

A few more more.....

And a couple more...

Lab Report on the Spectro P-202 Amp. June 1976.

Very positive review.. ;D

Just found a 200SR on epay for under a C note shipping incl. and took a chance. Listed as powers up but not tested. As I don't have one in the collection it will be a nice addition.  :)

That's a great price for the amp. A couple of months ago, I bought one on E-Bay for our PA system at MidNite. I paid more that they sold for 35 years ago.

Well........sure sucks when people have no idea on how to properly pack heavy items. Particularly vintage/classic audio gear. :(

What was a very nice condition 200SR showed up with severely bent rack mount ear ends. Bezel/display area is OK though. Right SCAMP is DOA. left side is good but Led Zepp in Mono does not cut it.. Pulled the bad SCAMP last night and will check the transistors today.

Robin, you posted earlier those are/were Motorola MJ15024 if I recall? Same ones used on the 500SR? And Robin when cleaning out the garage don't forget about that NOS 200SR double faceplate in a box back in the corner......:)

boB thought maybe it was Jeff at Optimum that did those plates for Spectro way back but Jeff says it wasn't him.

parcel loader thinking to self...." Hmmm, it's heavy!  Must be tough.  I'll test that for him...."

Quote from: Westbranch on April 30, 2015, 06:32:04 PM
parcel loader thinking to self...." Hmmm, it's heavy!  Must be tough.  I'll test that for him...."

Test is right! Seller was kool and refunded about half so at this point I'm in it about $50 so a decent reduction in pain. Still ticks me off when careless folks are allowed to leave the hospital after birth.

Found two of the output transistors on the SCAMP board dead. I plan on rebuilding both SCAMP's since I'm in this far anyway. All the caps too.

Robin, do you still have the schematic in PDF for the 200SR?

I do have some sort of 200 schematic. All I have to do is find it! The transistors are indeed MJ15024's. We usually had to replace the T0-220 drivers on the stand up heat sinks also.
I will keep looking. We have those transistors at MidNite, so if you have trouble finding them, come on up and we will give you some.

(https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQzYQBbHgY4DW9IIVMT4kMe-Bs_iF_8jsxp2vI-LCZxiCpbYD8un0K-Qw)


so who was this "boB was Here"??

Quote from: Robin on April 30, 2015, 09:06:46 PM
I do have some sort of 200 schematic. All I have to do is find it! The transistors are indeed MJ15024's. We usually had to replace the T0-220 drivers on the stand up heat sinks also.
I will keep looking. We have those transistors at MidNite, so if you have trouble finding them, come on up and we will give you some.

Well dang twist my arm! Planning a trip up maybe next week and will bring that HD I loaded up with a gazillion tunes for your PA.

Noticed somebody put a bridge on the bad SCAMP, not there on the good one and doesn't look like anything spectro would have done.... Couple pics of it.

Here are a couple of diagrams of the 200. There is one more that may be a duplicate. I will send it in a separate message. Files too big.
You might be able to talk Bob into helping to fix your amp. Bring it up.

Here is the last 200 diagram I have.

Quote from: Robin on May 01, 2015, 12:23:02 AM
Here are a couple of diagrams of the 200. There is one more that may be a duplicate. I will send it in a separate message. Files too big.
You might be able to talk Bob into helping to fix your amp. Bring it up.

Thanks for finding those Robin! The only thing I would need to bring up would be the SCAMP that has been modified with that wire bridge. boB should be able to finger it out just seeing it. pics here may be enough too. R n R bad devices and old caps is easy but when somebody has gone off the reservation with the original design is where I get lost...:)

Bob may not be able to do anything without the rest of the amp. He may be able to get it running. I do not think those other two parts were ours.

Quote from: Robin on May 01, 2015, 01:48:33 AM
Bob may not be able to do anything without the rest of the amp. He may be able to get it running. I do not think those other two parts were ours.

I know the power supply and other SCAMP are OK. Wired up a 220R to my 217R and cranked it up. Sounds great and display functions correctly. Just the one dead and bastardized SCAMP.

I catch him several days a week in the mornings on his way in and we swap lies on one of the VHF repeaters near Everett. I'll try to catch him tomorrow or early next week and see what he thinks. Did talk yesterday about it briefly so he is in the loop.

Just for the record, that resistor in the tubing soldered to the back of the board was most likely
done at Spectro.  It is a resistor tied from one of the power voltage rails to one of the diff-amp
inputs to mitigate too much DC offset on the output of the amp.

I remember this trick for several amplifiers, not just Spectro Acoustics.
But I seem to remember that we did this at Spectro once in a while.

boB

boB had looked around but did not locate any of the MJ15024 output transistors. He gave me a couple of great sites to check though, one is https://octopart.com/ you can punch in almost any device number and they return numerous hits on other sites that stock them. Thanks for that link boB!

I stumbled on an ebay seller that had them at a good price and their feedback was 100% excellent history etc. so I purchased 10, 2 spares just incase...along with one of the two drivers they had available. 2N6474. Found on ebay also what "appears" to be original RCA 2N6476 drivers. How do you really know? :(

Anyway....here is a pic of the 15024 tranny's as received, shipped in an...envelope! Seller replied promptly and is sending replacements in a "box"! Yes, I could straighten the pins but that's a pain and several are tweaked badly. Plus I would not trust them.

Now you'll have lots of spares...   ;D

amazing they are almost straight!  must have been 'gently' handled by the delivery agent...

for future reference, was it a bubble envelope?

Quote from: Westbranch on June 02, 2015, 06:58:08 PM
amazing they are almost straight!  must have been 'gently' handled by the delivery agent...

for future reference, was it a bubble envelope?

Yes on the "bubble envelope"  :o

It's alive!  :) Replaced the drivers and power transistors last night on the dead SCAMP. Brought it up slowly on a variac......no magic smoke! 14mv DC on the repaired SCAMP output and about 67mv Dc on the other one. Want to get that a bit lower and might try the resistor trick boB mentioned in a prior post.

It was late and I was getting tired but I did a brief test with some input. LedZep sounds much better in stereo!! Next step is replacing all the caps and see about making up a new faceplate.  :)

The way it should be... :)

The display we did on the 200SR is pretty cool for the time. How does it sound?

Quote from: Robin on June 15, 2015, 08:13:59 PM
The display we did on the 200SR is pretty cool for the time. How does it sound?

It sounds great! Been running all day at low volume and keeping an eye on temps etc. It's staying cool but I'm uncertain on how to adjust the bias? Tried using the same procedure as the 500SR manual shows, but no difference on the fluke voltage wise. Did not turn the pot on one side much either direction and ended up putting it back where It was.

I did crank it up to all of about 25-30 watts for a short period and again no abnormal temps. At low volumes all 8 of the 15024 collectors are at 80-85F.

The drivers on the unrepaired SCAMP are about 10-15F higher though than the repaired SCAMP side.
105F Vs. 115-120F. Not sure if that's a big deal or not. Ambiant room temp is 78F right now and the big heatsinks on both sides are cool to the touch.

No distortion, very clean audio. At least to my ears.  ;D

Display is still KOOL today! Timeless design.. :)

If my memory serves me correctly, we used to set the bias pot using a distortion meter. Too much one direction and the Scamp runs cool, but has higher distortion. Too much the other way and it runs too hot. I don't think it would hurt to try to make the repaired Scamp run the same temperature as the old one/ Just watch for run away temps.

Quote from: Robin on June 15, 2015, 10:44:44 PM
If my memory serves me correctly, we used to set the bias pot using a distortion meter. Too much one direction and the Scamp runs cool, but has higher distortion. Too much the other way and it runs too hot. I don't think it would hurt to try to make the repaired Scamp run the same temperature as the old one/ Just watch for run away temps.

The ear also does (usually) a pretty good job of detecting distortion.  In this case, the bias controls zero-crossing distortion
which ~should~ be most discernible at a low-ish level because then, the zero-crossing will be more of a signal compared
to the whole signal.  Applying a sine-wave to the input at a frequency of around a couple kHz should be good.

Could make one on the computer OR download a .WAV file from the internet somewhere.  Just make sure it's a good sine-wave
used.  Then, turn down the playback volume until you can just hear it and then turn it up a little bit more.
Adjust the trim-pot until you can hear some distortion.  If you can NOT hear any distortion, then maybe bias turned
down is good enough ?

There may also be some speaker noise or rattling in some cases.

The newer "modified" SCAMP modules that have the 8 pin op-amp near the input of
the module are the ones with more negative feedback, which makes the crossover
distortion better with a given trim-pot setting.  That trick significantly reduced the THD
including crossover distortion.

It may be that these modified amp modules are so good that you actually CAN turn the trim-pot
down all the way or almost all the way.

Your value may vary with age etc....

boB

Thanks boB & Robin! I'll give the sine wave to the input a try and see if my old ears can detect any distortion.  :)

I did run it again all day today at an increased volume...almost enough to rattle the windows and no abnormal temps. Was going for a moderate stress test and it's holding up fine.

During the "stress test" ....I came across some more SA "GOLD" literature as luck would have it. Here it is...First up the 210

Have to mutli post to get these to fit. Rest of the 210.

Next up the 101B

101B part 2

Next up the 217

Time for some amps....202

And now....the 500/500SR.  :)

OK, correction: This is the way it should be! Note level indicators are maxed out...Cranked the 200SR wide open for an hour and a REAL stress test!  ;D

This was into some JBL TR225 4 Ohm speakers. Very clean at max volume with no distortion. Just had to share some WHO and Black Sabbath with the neighbors... :) All magic smoke is still inside the 200SR... ;)

Here we go again... :) Just snagged a 217R purchased new March 1980 serial #0009! And another 200SR purchased new June 1981 serial #0072. Both in very good condition. Asked the seller to "double box" both and ship individually. Fingers crossed they will get here undamaged.... ::)

Both arrived undamaged.... :)  Pics to follow. Meanwhile here is the performance spec sheet SA included with it when shipped.

Finally got around to some bench testing time. Pre-amp has a broken power/level switch. boB thinks he may have one in the back of a drawer....:)

Brought the amp up slowly on a variac.....but after a few minutes at 120VAC it popped one of the filter caps. :(
Replaced both caps and fired it back up.....no magic smoke escaped and after a few hours I gave it some input and all is good. Very dirty/dusty inside so a thorough cleaning is in order.

A few more pics....

It's a neat feeling getting one of these in rough shape and bringing it back to life. The thing about these amps is that they were built with rugged in mind and it's possible to completely overhaul them with replacement parts. I will post a list of a couple of transistors that are replacements that I was able to find.

I just got another one from Ebay and I'm starting on it. My last one I ended up going with the original midnight blue design (very forward for the era and looks as contemporary as anything today). I removed the internal lamp reflectors for the clip lights and brought them right into the left and right plexi windows, also added  a black baffle behind them so that you can't see the amp interior. They look like mini vacuum tubes when they illuminate (kind of retro which is a bit trendy at the moment). I also got rid of the red plexi in those windows and replaced with smoked. Then I painted the trim bezel and the faceplate to cover up the gold pin striping and the model number. I'm probably going to put that guy on Ebay soon and work on the new one. Super crystalline highs and really punchy lows.  I was playing around with a faceplate design for the 202 that would utilize the existing clipping indicators, but behind some sleek yellow slits and then replacing the backlit analog bulb array with a simple bright LED (the arrows shown are just guides for lining things up.

Very nice find, Ingot !!

boB

I'm new to this forum which I found only a few days ago and I like it. By the way, i've had a Spectro 2102 EQ since jan. 1979 and a 217R preamp since June 1979 (36+ years !) both are still working fine, the EQ is all original and I only had to clean the switch on the front panel with Caig's Deoxit F5 and still going like new. As for the preamp the only repairs to it were some RCA connectors on the back panel which have a tendency to break because of their plastic holder does not resist the test of time... also some Deoxit on source selector switches and on/off/volume control but that's it, still going on strong. I guess Robin would be proud of his work to hear about these survivors !
I am considering giving away the preamp (yes for free) to the right person who will have to have it shipped at their own cost from Montreal, Canada since I use it less because my setup has changed, I'm also getting older and use less Equipment  and I have two other more recent  preamps. Let me know if you are really interested. I am keeping the EQ for my setup, too bad for you guys... 

Richard

Hey Robin and Bob, Spectro brings back some memories. Good people making quality stuff,working hard but in mellow atmosphere, lunch at Alfy's{two for one},Space Invader's Alfy's Pizza, Great Christmas Party (driving Robin's go-cart in the snow, flying though the air (from one level of the parking lot over some stairs to a lower level). Not sure if you've ever heard that story, lucky I was going pretty fast! Those were the best of times.   Jim

Ahhh yes, Jim !  Space Invaders !  I remember that was one game that Robin played and it was so cool to see video games
way back in the early days of computers !  Those times are gone for good !

boB

Hey Robin, Bob and others, speaking of memories and of the good old days, no takers on my offer (see Dec. 14 2015 post above) for a 36 years old and still working fine Spectro 217R preamp with user manual included ? The right person is simply anyone who will use it in a hi-fi or pro gear setup and enjoy it for a few more years.  I will package it carefully and drop it at the carrier of your choice (Postal service, Fed Ex, UPS, etc.). I can provide the unit's serial number if you want. Being in the process of downsizing and reorganizing my home studio gear, if you insist I may even chip-in in the future the 2102 EQ with user manual, since I have other more recent EQs from Rane... This is the last call guys, wake-up time !

Richard

May this link be fixed please? I would love to acquire some documentation....Thanks in advance for any help here in.

Quote from: boB on February 10, 2014, 02:50:25 AM

Here it is !

http://k7iq.midnitesolar.com/spectro%20500%20test.pdf

boB

The powers above me moved all of those files and I don't quite know where that particular k7iq directory went ?
I hope that Ryan moved it too but I haven't looked recently.  We'll find it eventually I hope.
boB

I may have the manuals. Email me.
Robin@midnitesolar.com.

New guy here, this thread has been most helpful.  Just purchased a 217R preamp--haven't received it yet--and it's so damned hard to find out any info at all.
Been doing stereo/hi-fi stuff for over 50 years, love turntables and preamps.  Hoping the 217R is my Goldilocks pre.
Anyway, what's the difference between the 217 and the 217R?

The 217R has a rack mount face plate. That is the only difference.

How about the headphone jack?  Judging by the pictures, not all 217s have the headphone jack.
Which is the biggest surprise of all.  The 217 is an outstanding headphone amp if nothing else.  Can't believe how much better my headphones sound over the DB amp I've been using for the last ten years or so.

I forgot about the headphone jack.
It is just in parallel with the output.
When Brian Morrison designed the 217, it was the first all integrated circuit preamp. We did not do this because of technology. I believe it was just the easiest way to do it. IC's that were capable of this application were very new so we took advantage of it.
None of the Spectro engineers had any formal schooling in electronics. We were just all passionate about electronics.

I don't think that MY 217R has a headphone jack ?   Did I get a raw deal ?

Happy new year-ish !

Quote from: boB on December 30, 2018, 02:06:35 PM
I don't think that MY 217R has a headphone jack ?   Did I get a raw deal ?

Happy new year-ish !

boB, I think you had some connections at SA.... Got a deal on an early model?  :) My #009 has no jack, but #440 does.

Hi all ;D Name is Paul (I've used Kryten42 online for years & most people who know me use that). Live in Australia (Victoria).

Don't know if this thread is still active, but I had to reply! This was a memory overload for me. Awesome!

I saved for almost three years to build my dream Super Hi-Fi system. I got almost every Audiophile mag published! I was an apprentice Studio Engineer & session drummer in the late 70's, went back to College then Uni & became an Industrial Design Engineer (retired now).

I was excited when a new large Audiophile store opened in a Melbourne suburb called Richmond (I forget it's name now) around 1978. I spent as much time there as I could until 1980/1 when I had enough $ (with a nice discount & a bonus from the studio) to buy my dream. They asked if I could get them some time in the studio sound lounge as they wanted to set up their own for testing & customer listening without annoying the whole suburb! They offered me and the studio a nice discount & the boss agreed. We all got a lot out of that & the studio bought a lot of gear from them. I got a phone call one day to tell me that had some new US gear I'd be interested in. I sure was! Because of that, the studio & I bought what might have been the first Spectro Acoustic's gear & EV D's in AU.

My system ended up being:

Rega Planar 3 Turntable with Rega-Acos R200/Ortofon MC 20 MK II (originally), SME Series III/Ortofon Concorde 30 later.
Technics SL-10 Linear Turntable, later with Ortofon OMP30 T4P MC Cartridge
(I couldn't decide! I have broad music tastes & some sounded bettor on one or the other).

Spectro Acoustics 217R Preamp
Spectro Acoustics 210R Equalizer
Spectro Acoustics 500R Power Amplifier
Spectro Acoustics 220R Tuner

ElectroVoice Interface D Speakers

AKG K340 Headphones

Some time after I got that, the store called to say they had a Valve Amp I'd be interested in (I was looking for a decent one to play with). They'd found a Fisher (The Fisher) A-202-B in perfect condition. I grabbed it! They threw in some Polk Cobra Cable (they weren't actually manufactured by Polk, just marketed. I think they were made in Japan if memory serves) & said they'd probably work best with The Fisher. I read some horror stories about these cables & ran a lot of tests with some Tektronix test gear I had at the studio & found that the stories were mostly garbage. They worked fine on both systems for years & neither amp exploded!

I was such a geek back then! Still am to be honest. ;) :D

I loved that system for years. Thanks for the memories.  ;D

Kryten, than you so much for the story !    That's great !

Do you have some old HiFi magazines from back then that might have any of our ads ?

I can't remember much about which magazines we advertised in ?  I remember one ad, which I ~think~ was a full page ad was of Eddie Money standing next to a fancy expensive car and also one of our racks of gear  (which was his payment for the ad)
The title was "It's Only Money"

Hi boB  :D Thanks for replying. It was a good time & worth the memories.

You know... I think I do remember that ad! I did keep most of the mag's & I had complete series of Electronics mag's that became collectors items. Sadly, I lost the majority in 2009 in a flash flood. I'd moved to a town in Central Victoria & we'd had a long drought. One day, late in 2009 not long after I'd moved, the skies opened and we had a torrential downpour lasting more than a day. Most of my boxes of mag's, books, documents & some gear I'd kept (Rega P3 & Fisher Amp & some other bits) were kept in the garage as the house had a decent carport where we kept the car, so we thought the garage would be good for temporary storage until we got around to sorting things. We were near the bottom of a hill & the driveway had about a 15deg slope. It flooded quickly & the water had nowhere to go. Almost everything was destroyed. Lost several photo albums... It was a bad time honestly. But the past is the past & I still have some good memories.

With my job as an Engineer & eventually Project Manager & Consulting Engineer, I got to travel around the World a lot. I worked in the USA for GD on a joint US/AU project for over a year. Saw a lot of the USA... Well, a lot of airports, hotel's, motels, GD facilities & USAF bases!  ::) :-\

I really missed working as a studio engineer (and roadie on some big gig's, Kiss Concert in 1980 was the last one, I was busy with College again. Biggest open-air concert in our history I believe). It was a lot simpler & I had time to enjoy things, you know? I miss that system too. I spent about 2 years planning and dreaming! 8) :D Oh! I think I saw an ad for SA in Radio-Electronics, maybe? One of those mag's like that.

Anyway, now I am retired, I have time on my hands! So who knows... Maybe I'll build a new *dream*! ;) :)

That's too bad about the flooding, Kryten...

I spend many years in audio working at various companies around the northwest.  Mainly pro-audio stuff.

Mixers and compressors and all sorts of stuff.  Always had some kind of basement or living room studio to play in !

boB

Hi,

I'm servicing a Spectro Acoustic model 202 amplifier (no opamp) and it works ok but stays too cold to my taste. I varied the bias trim pot and it does not seems to change anything. Without any signal, I measure 0v the 0.33ohm (edited) emitter resistors. Any help would be appreciated.

Thank you.

Quote from: Beauregard on December 21, 2019, 11:21:22 PM
Hi,

I'm servicing a Spectro Acoustic model 202 amplifier (no opamp) and it works ok but stays too cold to my taste. I varied the bias trim pot and it does not seems to change anything. Without any signal, I measure 0v the 33 ohm emitter resistors. Any help would be appreciated.

Thank you.

Is it working otherwise ?  Maybe the bias circuit is somehow kaput and not allowing the bases of the top and bottom output transistors to separate in voltage from each other  ?

Do you have a schematic of the 202 module ?  I'm going off of memory but I think there might be a fixed resistor across the trim-pot ?  Maybe it needs to be taken out of circuit or raised in value ?

Zero volts across the emitter resistors is not right of course.  Can't remember what should be measured there ?  Maybe 5 millivolts or so ?

Hi boB, thanks to chime in!

It works but I think the distorsion could be less. The emitter resistor is 0,33ohm, my bad. I'd  be happy to measure 5mv but last time I checked it was really 0mv with my fluke 87. After two hours being on (no signal), both heatsink don't have any heat.
The schematic I have has the opamp and maybe a few other differences with the actual circuit. I'll take a look when I'm at the shop.

Have a good night.

The only difference between the amplifier with and without the op-amp is that the one with the op-amp in the front end adds a gain of around 3X and then the amplifier feedback resistor changed from like, 27K Ohms to 8.2 K Ohms I think.

The bias circuit should be exactly the same in both and if the bias is working, should give you SOMETHING across the 0.33 Ohm resistor and/OR maybe make the main power transistors heat up a little bit without putting out any power.

Merry Christmas !

Quote from: onanparts on January 17, 2015, 04:02:02 PM
Now for the first time ever seen....as far as I know by anyone outside of Spectro Acoustics.

THE ROCK! The 600R Prototype Spectro Amp that unfortunately never saw the light of day until now.  :o

This was going to be the 500R's big brother. Massive heat sinks! It was very close to being completed when Robin and boB moved onto other projects. Maybe someday boB will have the time to bring this beast to life, but Midnite has his undivided attention with their numerous projects so it may be awhile, if ever. But I will try twisting his arm now and then about it.  :)

Well....Christmas came early for me a few weeks ago. Stopped in at Midnite for a Holiday visit. Didn't get much of a chance to snoop around and get any pics of the current Inverter program, B17, Rosie etc. as Robin thought I would have more fun helping him play musical chairs with his T-Bird collection....:)

Dead batteries and a few mechanical issues required relocating the birds using the push and pull method...all by hand..!

It wasn't all hard labor and I did get to see most but not all of the new much bigger facilities they have moved into. By the end of the day it was time for dinner, but Robin had a big sack for me, about 45 Lbs worth of sack to be exact! It was a nice sack even though I had to pick it up and haul it out to my car.....:)

So what was in Santa's sack? Well......Here is the lowdown....


After nagging both boB and Robin about bringing the "Rock" /600R to life the past few years, it appears I nagged Robin one time too many. Well, it has been gathering dust since about 1979........

Robin asked me if I wanted it? Hmmm..let me think about that for a microsecond...Sure! 🙂 Now it's on my bench with plans to get some voltage on the rails! No circuit boards were ever made for it but Robin has offered to help me design the boards from scratch for the Rock. I'm looking forward to getting the Rock out of mothballs and bring it to life sometime this year.

Thanks again to Robin for the "not available in stores" Christmas Present!  8) 8)

First look under the cover.

When I pulled the cover off and turned it upside down a couple outputs fell out.....:) NEC D746's surrounding a few Sanken 2SC2774's and 2SA1170's.

Hold on to those, TJ ! 

We'll use them in a new inverter or something !

Quote from: boB on January 05, 2020, 01:04:59 AM

Hold on to those, TJ ! 

We'll use them in a new inverter or something !

OK, an Inverter that does 350 WPC @ 4 ohms and 0.00000000000001% THD will be nice. Time-varying system behavior must be minimal or non-existent......and none of that THD+N crap! Just keep the notch filters in the drawer!  :)

Hmmm....so it was just the other day, really! It was.....

The mysterious RobKen Pre Amp, # 22 of 23 shows up. :)

Maybe next time I'm at Robin's he will pop the cover off for a few pics?

And a "Nauti Rob" ??? Robin, you gots some splaining to do....:)

The name on the back of the RobKen preamp is Greg Johnston...

Greg was an owner of Trace Engineering and Magnum Energy.

Steve Johnston's brother. 

I remember when Greg was one of the production leads at Phase Linear back in the early 1970s

Robin still has the working prototype of the SA P-202 amp. I did not get any good pics of it except for one SCAMP board. Again, next time up to Arlington maybe I'll have the chance to get some nice pics, along with more of Robins SA gear he is taking out of storage. All the SA gear he has is going in a big system soon to be up and running. :)

Hmmmmm....been a couple years. I did say I would post some topless pics of the RobKen Model 5000. Well, I was out at Robins recently and he was looking for a good home for the RobKen and several SA prototype amps and pre amps. After twisting my arm just a little...I agreed to adopt them! :)

A few pics of the RobKen topless....More to follow!

Spectro acoustic pre amplifier!  I win finally!

The only way my guesses are accurate...some broad hints  ;D