RARE VINTAGE AUDIONICS OF OREGON SPACE & IMAGE COMPOSER QUAD DECODER UNIT

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Akaiquadster2

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What are you trying to find out? It means that its unit 154 out of 300 (ish), probably a National Semiconductor modified chip unit, not the exar modified chip unit, although it would be around the time of the changeover and no one knows for sure exactly when that happened.
So which chip is off the block ? 😂 what’s the essential difference?
 

Marcsten

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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.
 

Marcsten

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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...View attachment 70311
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.
 

par4ken

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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.
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.
 

par4ken

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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.
 
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furui_suterioo

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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 scarp 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!
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.:)
 

Marcsten

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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.
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...
 

Sonik Wiz

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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.
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.
 

par4ken

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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?
 

chucky3042

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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.
I still have them somewhere
 

chucky3042

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Yes, but why ?
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

IMG_20210917_105049.jpg


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
 

Sonik Wiz

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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

View attachment 71430

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."
 
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