So which chip is off the block ?
what’s the essential difference?
RARE VINTAGE AUDIONICS OF OREGON SPACE & IMAGE COMPOSER QUAD DECODER UNIT
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what’s the essential difference?
I think the chip that's off the block is the one that doesn't fall too far from the tree!
As Steve explained it to me in 2016, the National Semiconductor chips were the originals but when they were delivered they didn't work. So Audionics had to design essentially workarounds outside of the chip. Theoretically, this hampered the speed of the tate system. Mine is a NS composer. I don't have any issues with it.
But Audionics wanted the chips to work correctly, so Exar took an NS chip looked at it under a microscope, found the problems and fixed the biggest ones, but not all, meaning Audionics again had to work around outside the chip to repair issues, just not as many as with NS chips. So in theory, the Exar chips are a little smoother and faster, if those are the right adjectives. I have a hard time telling the difference, frankly, but I am biased because mine is one of the early ones.
Its far more important to performance, in my opinion, to have a stable solid source from your cartridge/preamp and make sure to frequently check input balance with a test record.I do it pretty much every time I start a session where I am going to play matrix records. Steve confirmed that this was key to optimum performance.
As Steve explained it to me in 2016, the National Semiconductor chips were the originals but when they were delivered they didn't work. So Audionics had to design essentially workarounds outside of the chip. Theoretically, this hampered the speed of the tate system. Mine is a NS composer. I don't have any issues with it.
But Audionics wanted the chips to work correctly, so Exar took an NS chip looked at it under a microscope, found the problems and fixed the biggest ones, but not all, meaning Audionics again had to work around outside the chip to repair issues, just not as many as with NS chips. So in theory, the Exar chips are a little smoother and faster, if those are the right adjectives. I have a hard time telling the difference, frankly, but I am biased because mine is one of the early ones.
Its far more important to performance, in my opinion, to have a stable solid source from your cartridge/preamp and make sure to frequently check input balance with a test record.I do it pretty much every time I start a session where I am going to play matrix records. Steve confirmed that this was key to optimum performance.
So I have number 12006...
So I thought working out how a magnatomic flux warp drive was difficult but you make it sound like a breeze in comparison to playing some vinyl...
LOL. Not really. Takes about a minute or two to put on a test record and set up the input on a Composer. The LEDs are helpful in terms of being precise. But it makes a big difference.
A very early unit, making yours a Pioneer. Just not that Pioneer.
surround.sound.enthusiast
500 Club - QQ All-Star
Nice, mine is also an early unit: 12023.
Nothing to really set up except the input balance and that can be done on the fly. If your talking about the Axial Tilt, it's a real pain to set up as the pots are on the back and the test tones on the test records are usually very short. I didn't bother using it for years but more recently took the time to set it up. I was able to get about a 10dB improvement in left to right separation. The tilt corrected signals decoded noticeably better across the rear even (especially) when I tried playing the corrected signal via my Sony QSD-2010. That damn thing uses a bit of fixed blend across the rear, so needs all the help it can get IMHO.
Well I was getting tired of seeing this one for sale so I made a slightly higher offer than I had previously, after a couple of counter offers I was able to get it for much less than he was asking. If there ever was a candidate for a parts machine this one is it. The first thing I did was pop out the DES detector chip and plug it into my old unit, success after returning the adjustment pot to its original position it now works great.
So the old DES chip now is in the scrap unit. That being said there might still be hope for it yet. While I like having two composers one in the Living Room and one in the Man Cave, I don't really need three, BUT. As with the last unit the power transformer broke free from the board, so will need replacement before anything else. They are still available from Digi-Key for about $20, or I could cobble something together to test out the rest of the board. I can't believe that a seller wouldn't clean up the unit before selling. What looks like paint on the knobs are in fact scuffs possibly from pliers or vice grips as someone tried to remove the knobs? The transformer is rusty as are a couple of the screws but no sign of water damage to the board. Some of the output jacks are badly tarnished as well. The unit obviously spent time in Canada it has an OPP (Ontario Provincial Police) crime prevention sticker on it. I might swap front panels with my original unit as the silk-screening around the volume knob on mine has worn off after 40 years of use. A small sticker inside beside the oddball 17xxx serial number has two dates in 1981 and what appears to be Steve Kennedys initalls. It sure would be nice to learn the story of this, was it procured by someone at Audionics how did it make its way to Canada how did it find its way back to the states! How did it end up in such deplorable condition.
So the old DES chip now is in the scrap unit. That being said there might still be hope for it yet. While I like having two composers one in the Living Room and one in the Man Cave, I don't really need three, BUT. As with the last unit the power transformer broke free from the board, so will need replacement before anything else. They are still available from Digi-Key for about $20, or I could cobble something together to test out the rest of the board. I can't believe that a seller wouldn't clean up the unit before selling. What looks like paint on the knobs are in fact scuffs possibly from pliers or vice grips as someone tried to remove the knobs? The transformer is rusty as are a couple of the screws but no sign of water damage to the board. Some of the output jacks are badly tarnished as well. The unit obviously spent time in Canada it has an OPP (Ontario Provincial Police) crime prevention sticker on it. I might swap front panels with my original unit as the silk-screening around the volume knob on mine has worn off after 40 years of use. A small sticker inside beside the oddball 17xxx serial number has two dates in 1981 and what appears to be Steve Kennedys initalls. It sure would be nice to learn the story of this, was it procured by someone at Audionics how did it make its way to Canada how did it find its way back to the states! How did it end up in such deplorable condition.
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furui_suterioo
Quad & 70s Enthusiast
Glad you were able to salvage the detector chip from that one. Mine is on the operating table right now getting recapped. The plan/justification is if the Tate chips ever blow out in the future, I'll have at least one working replacement DES set from my two Dolby Tate cards, it's a gamble but that's what happens when you become a Tate fanatic.
Glad you got a needed working chip out of the scrap unit. Saw it on Ebay and it looked really rough, to say the least! Poor old thing! The number issue other than someone at the factory taking it is likely a story lost to time, like where all my left socks go when I put them in the laundry...
Congrats on the purchase & I'm glad it now has a forever home. It's an expected situation dealing with very vintage quad gear to have at least one spare device for parts. Tate and Variomatrix chips are the most needed. And for some starnge reason @chucky3042 has a good collection of the sets of Sansui chips. I don't know why /how he got them or for what purpose (I'm sure it's an interesting story) but if I need one Chucky would be my first go to attempt.
The Sansui chips are available from several sellers on eBay as well. I still have a few spares. I swore that tri-banding was a terrible idea until I went to align the QSD-1 and found that the midband decoder was not functioning correctly, it was much better after replacement. Too bad there isn't a supply of Tate chips somewhere. I wonder what Audionics did with the National chips that they replaced with Exars?
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I still have them somewhere
Yes, but why ?
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Hi Sonik
It was in the very early in the development of the SM and I wanted to do some tests on how they did it. In the end I got the chips and did nothing with them. Instead I went full INVOLVE and ignored most aspects of their approach (in particular their method of phase detection) and implemented a discrete IC analogue based surround master prototype
The damned thing actually worked. Only problem was wandering tolerances and a very slight background whistle sound on the VCA's that I never resolved!
Next was getting it all into software DSP land
I thought the Sansui method of direction sensing was unique & an advancement of prior art for the time. If you feed the 2ch input to a high gain limiter with 60dB range, then with in that range there is essentially no amplitude difference. So if you feed it into a differentiating circuit what would it be differentiating? Phase difference between the chs. A pretty clever way when most others were using a standard log circuit with a transistor in the feedback loop. Many challenges to this.
But with fast acting RMS & averaging circuits available today & even in software, I think that is the better & more direct way to go, which I guess was Involve's path.
I've seen that protype pic before & it is a cool bit of Involve history. Like the current Surround Master I am impressed that there are no trim pots (at least visible) to tweak the decoding. In my Proton (Aphex) SD1000 there are 24 trim pots to be adjusted for proper decoding! And I rememebr Fosgate talking about his SQ decoder prototype using the Tate DES. No SMD stuff... it was described as "filling the size of a kitchen table."
Last year I made an offer on that Composer that was in terrible condition. I used the Exar DES chip to get my original unit working 100% again. Now I've slowly been working on that beat up unit.
First off it needed a power transformer. I've seen this happen twice already that the transformer gets broken usually during shipping. Thankfully the very same transformer is still available. I purchased it from Digi-Key. Mouser also stocks it. Signal Transformer DST-6-36. It sells for about $20.00.
The RCA jacks were badly tarnished so I replaced them with similar ones also from Digi-Key, CUI-INC RCJ series. the originals were all red I bought half red and half white to colour code left and right inputs and outputs. Other colors are available so you could colour code all four channels if you wanted. I bought enough to do my 3 Composers plus a few spares but I'm not in a hurry to do the others they are still in much better shape than this unit. Like everything they are cheaper the more you buy.
Power Supply capacitors were changed 2200µF 35V replaced by 3300µF 50V. The coupling capacitors were replaced with Polyester 10µF film types bypassed by 0.01µF Polystyrene.
Yes it does work but could use that DES chip.
First off it needed a power transformer. I've seen this happen twice already that the transformer gets broken usually during shipping. Thankfully the very same transformer is still available. I purchased it from Digi-Key. Mouser also stocks it. Signal Transformer DST-6-36. It sells for about $20.00.
The RCA jacks were badly tarnished so I replaced them with similar ones also from Digi-Key, CUI-INC RCJ series. the originals were all red I bought half red and half white to colour code left and right inputs and outputs. Other colors are available so you could colour code all four channels if you wanted. I bought enough to do my 3 Composers plus a few spares but I'm not in a hurry to do the others they are still in much better shape than this unit. Like everything they are cheaper the more you buy.
Power Supply capacitors were changed 2200µF 35V replaced by 3300µF 50V. The coupling capacitors were replaced with Polyester 10µF film types bypassed by 0.01µF Polystyrene.
Yes it does work but could use that DES chip.
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My third Composer is functional with the exception of the DES direction sensing chip. I'm thinking of just using it mainly for the Axial Tilt circuit. With my current recording set up I go through the Composer using the tilt correction then to the computer's sound card input. The problem that I have is that when I play the recording during editing via the same audio editor I get some low level feedback as the sound cards inputs are still active. It is a pain to have to disconnect the input cables or mute the inputs via the sound cards control panel.
When I first got my original Composer I wrote Steve Kennedy suggesting among other things that the unit should have a tape monitor. That would have added cost to the already expensive product. Most vintage decoders do have a tape monitor (most useful if you have a three head machine). Even if the tape output was switchable would be a useful feature, but I digress.
Why use the Axial tilt anyway? For years I didn't bother as it is such a pain to adjust, most test records have test tones that are far too short, and the pots are awkwardly placed on the back of the unit. I started using it a couple of years ago.
With my Sony cartridge I was able to improve separation from just over 20 dB to almost 30 using the tilt circuit! Using the new Audio Technica cartridge the improvement was less, a few dB maybe. When listening to stereo that improvement is not even noticeable. It did seem to have the biggest effect when tilt corrected recordings were decoded with other (lesser) decoders. The tilt correction circuit is similar to Sonics pre-synth/phase balance circuit, just that it operates over a much smaller range, adjusted to cancel out the crosstalk in the opposite channel. It would be a very easy DIY project.
The S&IC comes stock with TL074 quad op-amps. To tweek better sound out of them Audionics ran them in Class A. That was done by means of a 2.2K resistor from each op-amps output to the negative or in some cases the positive supply rail. Over the years I swapped op-amps to the AD713. Close enough to the TL074 that the mod is likely still a good fit. I tried the OPA4123PA but they were unstable, I don't know if that was because of their wide bandwidth or because I bought them from a Chinese seller and so may be fakes! More recently I bought some LME49740 from a U.S. seller depleting his supply. Sadly the LME49740 has been discontinued. There are lots for sale from China at attractive prices but they are likely fakes. I just ordered some more LME49740 from a U.K. seller. I used one to make my active adjustable Dyna type decoder, they have an incredible CMRR (typical 120 dB), blending the stereo signals out of phase with each other using one of these almost totally eliminates the vocal. That attribute has got to be a plus in a matrix decoder! They seem to work/sound fine simply dropped into the Composer. I'm in a bit of a Dilemma, is class A operation beneficial with this op-amp? It has such low distortion already, it is possible that the added resistors are now degrading performance?
Audionics glued heatsinks to the chips running class A as they do run warm. The Composer with the old National chip set has no heatsinks on the chips. I guess that it was an afterthought.
As a test I removed the resistors from the crippled (third) Composer and installing my last LME49740 the rest are AD713 and one TL074 . It still sounds fine to me with mostly the old op-amps still installed and no class A.
I intend to upgrade all units by substituting the LME49740. My dilemma is do I leave in the resistors and hope for the best. Do I remove them from all units still hoping for the best. Do I replace the resistor with a JFET, JFET Cascode, Current Regulating Diode or change it's value, 2.2K always seemed rather low. What current is optimum, is this class A thing totally unnecessary. I'm leaning toward the latter.
Here is a very interesting link about Class A biasing of op-amps.
https://tangentsoft.com/audio/opamp-bias.html
When I first got my original Composer I wrote Steve Kennedy suggesting among other things that the unit should have a tape monitor. That would have added cost to the already expensive product. Most vintage decoders do have a tape monitor (most useful if you have a three head machine). Even if the tape output was switchable would be a useful feature, but I digress.
Why use the Axial tilt anyway? For years I didn't bother as it is such a pain to adjust, most test records have test tones that are far too short, and the pots are awkwardly placed on the back of the unit. I started using it a couple of years ago.
With my Sony cartridge I was able to improve separation from just over 20 dB to almost 30 using the tilt circuit! Using the new Audio Technica cartridge the improvement was less, a few dB maybe. When listening to stereo that improvement is not even noticeable. It did seem to have the biggest effect when tilt corrected recordings were decoded with other (lesser) decoders. The tilt correction circuit is similar to Sonics pre-synth/phase balance circuit, just that it operates over a much smaller range, adjusted to cancel out the crosstalk in the opposite channel. It would be a very easy DIY project.
The S&IC comes stock with TL074 quad op-amps. To tweek better sound out of them Audionics ran them in Class A. That was done by means of a 2.2K resistor from each op-amps output to the negative or in some cases the positive supply rail. Over the years I swapped op-amps to the AD713. Close enough to the TL074 that the mod is likely still a good fit. I tried the OPA4123PA but they were unstable, I don't know if that was because of their wide bandwidth or because I bought them from a Chinese seller and so may be fakes! More recently I bought some LME49740 from a U.S. seller depleting his supply. Sadly the LME49740 has been discontinued. There are lots for sale from China at attractive prices but they are likely fakes. I just ordered some more LME49740 from a U.K. seller. I used one to make my active adjustable Dyna type decoder, they have an incredible CMRR (typical 120 dB), blending the stereo signals out of phase with each other using one of these almost totally eliminates the vocal. That attribute has got to be a plus in a matrix decoder! They seem to work/sound fine simply dropped into the Composer. I'm in a bit of a Dilemma, is class A operation beneficial with this op-amp? It has such low distortion already, it is possible that the added resistors are now degrading performance?
Audionics glued heatsinks to the chips running class A as they do run warm. The Composer with the old National chip set has no heatsinks on the chips. I guess that it was an afterthought.
As a test I removed the resistors from the crippled (third) Composer and installing my last LME49740 the rest are AD713 and one TL074 . It still sounds fine to me with mostly the old op-amps still installed and no class A.
I intend to upgrade all units by substituting the LME49740. My dilemma is do I leave in the resistors and hope for the best. Do I remove them from all units still hoping for the best. Do I replace the resistor with a JFET, JFET Cascode, Current Regulating Diode or change it's value, 2.2K always seemed rather low. What current is optimum, is this class A thing totally unnecessary. I'm leaning toward the latter.
Here is a very interesting link about Class A biasing of op-amps.
https://tangentsoft.com/audio/opamp-bias.html
Last edited:
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You wont hear any difference (you will think you do!)
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