(1975-10) R-E mag - QS Matrix - Simplified

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kfbkfb

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QS-encoding can he expanded and developed, if necessary, to incorporate three or four transmission channels in a 4-3-4 or 4-4-4 system


It would have been interesting to combine QS with a CD-4 type carrier (only 1 carrier w/a high level of NR) to create a 4-3-4 system for users who wanted it and had a phono cartridge w/FR >20kHz (no channel separation above ~20kHz would be needed).


Kirk Bayne
 

par4ken

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QS-encoding can he expanded and developed, if necessary, to incorporate three or four transmission channels in a 4-3-4 or 4-4-4 system


It would have been interesting to combine QS with a CD-4 type carrier (only 1 carrier w/a high level of NR) to create a 4-3-4 system for users who wanted it and had a phono cartridge w/FR >20kHz (no channel separation above ~20kHz would be needed).


Kirk Bayne
A matrix/discrete record has been talked about here in other threads. In fact that idea was used in the UD-4 system. If only one subcarrier was used system design/requirements might of been easier. Personally I think that it would of impaired fidelity of the matrix portion because of the frequency band limiting required to allow for the subcarrier.

In that same magazine is the SQ synthesizer that I mentioned elsewhere. The inaccuracy of that article is how they describe it as using phase modulation. Yes signals are phase shifted various amounts by that circuit but there is no modulation involved! That circuit functions as a forward oriented SQ encoder utilising the back inputs only. That circuit can be made better by replacing the transistors with op-amps and replacing the selector switch with a four ganged pot, making the effect fully variable (the same as done with the S&IC)
 

Soundfield

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In that same magazine is the SQ synthesizer that I mentioned elsewhere. The inaccuracy of that article is how they describe it as using phase modulation. Yes signals are phase shifted various amounts by that circuit but there is no modulation involved! That circuit functions as a forward oriented SQ encoder utilising the back inputs only. That circuit can be made better by replacing the transistors with op-amps and replacing the selector switch with a four ganged pot, making the effect fully variable (the same as done with the S&IC)
Yes, Ken, interesting but that article wasn't very well written was it?! It didn't really explain what the circuit was doing and the stuff about 'modulation' was clearly written by someone who didn't really know what they were talking about. I would think it confused more people than it enlightened!
I was particularly amused by the bit that said "If you connect your synthesiser to an SQ or other decoder you might find that the result is a very strange sounding output" (without explaining why). I would have thought that would have made a lot of people think 'what's the point then?'!!!
 

par4ken

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Yes, Ken, interesting but that article wasn't very well written was it?! It didn't really explain what the circuit was doing and the stuff about 'modulation' was clearly written by someone who didn't really know what they were talking about. I would think it confused more people than it enlightened!
I was particularly amused by the bit that said "If you connect your synthesiser to an SQ or other decoder you might find that the result is a very strange sounding output" (without explaining why). I would have thought that would have made a lot of people think 'what's the point then?'!!!
My thoughts entirely. I don't think that the author understood what was going on. He seemed to have winged it, confusing it's operation with Sansuis pre Vario-matrix, "Phase Modulation" scheme he may of even plagiarized part of Sansui's theory of operation.

Yes connecting it to an SQ decoder is the only way to get surround out of it!
 

Soundfield

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My thoughts entirely. I don't think that the author understood what was going on. He seemed to have winged it, confusing it's operation with Sansuis pre Vario-matrix, "Phase Modulation" scheme he may of even plagiarized part of Sansui's theory of operation.
Yes connecting it to an SQ decoder is the only way to get surround out of it!
I was casting my eye again over that “4 Ch Synthesizer” article in the Oct 1972 edition of R-E. Apart from the flawed description of how it works, I am still puzzled by the references to it not working properly (!) if used with an SQ decoder-

Warning.JPG


This is strengthened by the note on the circuit diagram (which looks like a formal CBS Labs drawing) which states –

note 5.JPG


All rather odd. This thing appears to have only one purpose, to provide SQ encoded signals for an SQ Decoder. So why include those two transistors if they were never to be used in that very application?

Some clue is given in the (hand drawn) CBS Labs “Stereo to Quad Enhancement” paper describing the same circuit dated two years later (Dec 1974) as posted previously by @kfbkfb. Whilst there is not the same note on the circuit diagram the text does say-

cbstext3.JPG


These are the output buffers in question-
transistors.JPG

But I can’t really see why the use of this isolation stage, which seems perfectly sensible to me, should cause “a very strange sounding output“ if used with CBS own preferred SQ L1 or L2 decoder implementations. But If that were the case, why design it that way?

Any ideas as to what the thinking was here?
 

par4ken

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I was casting my eye again over that “4 Ch Synthesizer” article in the Oct 1972 edition of R-E. Apart from the flawed description of how it works, I am still puzzled by the references to it not working properly (!) if used with an SQ decoder-

View attachment 65630

This is strengthened by the note on the circuit diagram (which looks like a formal CBS Labs drawing) which states –

View attachment 65631

All rather odd. This thing appears to have only one purpose, to provide SQ encoded signals for an SQ Decoder. So why include those two transistors if they were never to be used in that very application?

Some clue is given in the (hand drawn) CBS Labs “Stereo to Quad Enhancement” paper describing the same circuit dated two years later (Dec 1974) as posted previously by @kfbkfb. Whilst there is not the same note on the circuit diagram the text does say-

View attachment 65635

These are the output buffers in question-
View attachment 65637
But I can’t really see why the use of this isolation stage, which seems perfectly sensible to me, should cause “a very strange sounding output“ if used with CBS own preferred SQ L1 or L2 decoder implementations. But If that were the case, why design it that way?

Any ideas as to what the thinking was here?
The author just didn't know what he was talking about!
 

Soundfield

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The author just didn't know what he was talking about!
Well that's true enough, but why did CBS themselves also say that two of their own circuits (one whose only purpose was to be connected to the other) wouldn't work together without modification? Perhaps I'm reading too much into this - I'll include the emitter followers if I build it, which as I've a couple of MC1312 chips lying about, I may well do to see how it performs feeding the SM.
 
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par4ken

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The buffers are there to lower the output impedance, they may not be needed depending on application (impedance of the stage that it is driving). Leaving them in will not cause any problem. Leaving them out you avoid one extra active stage that the signal has to pass through.
 

Soundfield

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The buffers are there to lower the output impedance, they may not be needed depending on application (impedance of the stage that it is driving). Leaving them in will not cause any problem. Leaving them out you avoid one extra active stage that the signal has to pass through.
Yes, that was my reasoning too.
 

chucky3042

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QS-encoding can he expanded and developed, if necessary, to incorporate three or four transmission channels in a 4-3-4 or 4-4-4 system


It would have been interesting to combine QS with a CD-4 type carrier (only 1 carrier w/a high level of NR) to create a 4-3-4 system for users who wanted it and had a phono cartridge w/FR >20kHz (no channel separation above ~20kHz would be needed).


Kirk Bayne
Such a great magazine. It was my favorite time in electronics.......Yes I am a 63 year old fart!
 

MidiMagic

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Those jumpers would require other circuit changes to not feed back.
 
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