Quantcast

(1974-12) SQ Stereo Enhancement [CBS Labs]

Help Support QuadraphonicQuad:

kfbkfb

400 Club - QQ All-Star
QQ Supporter
Since 2002/2003
Joined
Feb 20, 2003
Messages
478
Location
Midwest USA
It'd be interesting to try this preprocessing with the Surround Master decoder in SQ mode.

I'm not aware of any SQ decoders that used this CBS Labs devised SQ based Stereo Enhancement method.


Kirk Bayne
 

Attachments

Soundfield

1K Club - QQ Shooting Star
Joined
Dec 29, 2011
Messages
1,115
Location
Essex, UK
It'd be interesting to try this preprocessing with the Surround Master decoder in SQ mode.

I'm not aware of any SQ decoders that used this CBS Labs devised SQ based Stereo Enhancement method.


Kirk Bayne
Odd that they don't give an actual circuit. There is a lot more detail (but still no schematic) in Bauer's US Patent of 1976 "Method and apparatus for quadraphonic enhancement of stereophonic signals" -
US pat 3971890
 

kfbkfb

400 Club - QQ All-Star
QQ Supporter
Since 2002/2003
Joined
Feb 20, 2003
Messages
478
Location
Midwest USA
I wrote to CBS about SQ and received this mail, it does includes a schematic diagram, but in this digital age, I didn't think posting the diagram was useful.


Kirk Bayne
 

par4ken

1K Club - QQ Shooting Star
Joined
May 28, 2011
Messages
1,002
Location
NW Ontario
This is actually how the Space and Image Composer enhanced stereo, but by doing it directly rather than the stereo signal having to be pre-encoded. By swapping the front and rear decoder outputs and reversing phase we can produce this form of enhanced stereo.
 

kfbkfb

400 Club - QQ All-Star
QQ Supporter
Since 2002/2003
Joined
Feb 20, 2003
Messages
478
Location
Midwest USA
I haven't used "Scripts" for audio processing, it seems like it would be easy enough to process L and R with a 2 scripts (180 and 270 modes) and output L' and R' to feed to an SQ decoder.


Kirk Bayne
 

Sonik Wiz

2K Club - QQ Super Nova
QQ Supporter
Joined
May 30, 2005
Messages
2,063
Location
Kansas City
This is actually how the Space and Image Composer enhanced stereo, but by doing it directly rather than the stereo signal having to be pre-encoded. By swapping the front and rear decoder outputs and reversing phase we can produce this form of enhanced stereo.
How was it made variable in the S & IC?
I wonder how Fosgate did the stereo to surround in the Tate 2 decoders. The Sansui synth mode and the Fosgate both offered nice 270 deg wrap around. But the Fosgate sounded a little bit crisper in direction but the Sansui also enhanced center back which the Fosgate SQ method did not. The Sansui approach gave a bit more depth than Fosgate's.

In the SQ world there's no problem that can't be fixed by yet another 90 deg phase shift...
 

Soundfield

1K Club - QQ Shooting Star
Joined
Dec 29, 2011
Messages
1,115
Location
Essex, UK
I wrote to CBS about SQ and received this mail, it does includes a schematic diagram, but in this digital age, I didn't think posting the diagram was useful.
Kirk Bayne
I opted out of the digital age (!) and have a bunch of the Motorola chips - so I'd be happy to see it if you'd care to post it. Thanks.
 

par4ken

1K Club - QQ Shooting Star
Joined
May 28, 2011
Messages
1,002
Location
NW Ontario
How was it made variable in the S & IC?
I wonder how Fosgate did the stereo to surround in the Tate 2 decoders. The Sansui synth mode and the Fosgate both offered nice 270 deg wrap around. But the Fosgate sounded a little bit crisper in direction but the Sansui also enhanced center back which the Fosgate SQ method did not. The Sansui approach gave a bit more depth than Fosgate's.

In the SQ world there's no problem that can't be fixed by yet another 90 deg phase shift...
Basically you would just take the front and back decoder outputs feed them to each end of a pot, the output would then be a mixture of front and back, at each extreme pot setting it would give (normal SQ) with the pot fully counter clockwise and full enhancement with it fully clockwise.
This works in the Audionics decoder (check the matrix schematic), likewise it's how you build an encoder with a synthesize setting. Left front and right front are converted to left back and right back while center front stays put.
I'm sure that Fosgate decoders did the same thing but didn't make the effect variable.
 

Sonik Wiz

2K Club - QQ Super Nova
QQ Supporter
Joined
May 30, 2005
Messages
2,063
Location
Kansas City
Basically you would just take the front and back decoder outputs feed them to each end of a pot, the output would then be a mixture of front and back, at each extreme pot setting it would give (normal SQ) with the pot fully counter clockwise and full enhancement with it fully clockwise.
This works in the Audionics decoder (check the matrix schematic), likewise it's how you build an encoder with a synthesize setting. Left front and right front are converted to left back and right back while center front stays put.
I'm sure that Fosgate decoders did the same thing but didn't make the effect variable.
Didn't you do an article for the MCS Review that showed a DIY circuit for type of stereo to SQ surround? Or was that how to make an SQ encoder from a decoder chip?
 

kfbkfb

400 Club - QQ All-Star
QQ Supporter
Since 2002/2003
Joined
Feb 20, 2003
Messages
478
Location
Midwest USA
Here's the Schematic Diagram + Component List for the "Stereo-to-Quad Enhancer Encoder"

(I'm using a landline phone and had Dial-up until AT&T shut it down 2020-11, so I'm still technically in the analog age too :) )


Kirk Bayne
 

Attachments

Last edited:

Soundfield

1K Club - QQ Shooting Star
Joined
Dec 29, 2011
Messages
1,115
Location
Essex, UK
Here's the Schematic Diagram + Component List for the "Stereo-to-Quad Enhancer Encoder"
(I'm using a landline phone and had Dial-up until AT&T shut it down 2020-11, so I'm still technically in the analog age too :) )
Kirk Bayne
Thanks very much indeed - Very simple, I might give it a go!
 

Marcsten

400 Club - QQ All-Star
Since 2002/2003
Joined
Sep 24, 2002
Messages
491
Location
Seattle
This is actually how the Space and Image Composer enhanced stereo, but by doing it directly rather than the stereo signal having to be pre-encoded. By swapping the front and rear decoder outputs and reversing phase we can produce this form of enhanced stereo.
As I was reading Ben's paper, I thought the same thing - that the S and IC was the same in enhance, since this is how I play back almost all two channel source in my system. You get the extending of the stereo field, and out of phase info such as ambience is sent to the rears. I have used this for decades now and its my favorite enhanced mode. I should say that I have a QSD 2 but not the famous QSD 1 enhancement, so can't compare them.
 

par4ken

1K Club - QQ Shooting Star
Joined
May 28, 2011
Messages
1,002
Location
NW Ontario
Yes, I did a DIY article about building an encoder from a basic (non logic) decoder. I figured that one out myself from looking at the decoder output phasor diagrams and what was required as an encoded signal.

I think I did do another article adding forward oriented encoding and stereo synthesis, which are essentially the same thing. My inspiration for that came from "Quadraphile" and information contained in the US patents. I found out about the patent information from "Sonik's" article "Uncle Sam's Department of Quad"! A stereo to SQ "Enhancer or Synthesizer" similar to the schematic shared by Kirk was published in an electronics magazine (I forget which one) but that article contained some errors (in the description I think), I didn't understand how it was supposed to work at the time, because of those errors.

I know that I constructed several encoders for people that included normal, internal, forward oriented, and stereo to SQ synthesis. I used a Quad pot so that the enhancement effect could be continuously adjusted.
 
Last edited:

kfbkfb

400 Club - QQ All-Star
QQ Supporter
Since 2002/2003
Joined
Feb 20, 2003
Messages
478
Location
Midwest USA
Skimming the patent, I didn't find any mention of how the "enhancement encoded" stereo sounds in mono (I listened to FM with a mono clock radio until I got a battery powered headphone only FM stereo radio in 1984).


Kirk Bayne
 

par4ken

1K Club - QQ Shooting Star
Joined
May 28, 2011
Messages
1,002
Location
NW Ontario
The enhancement mode works the same as the forward oriented encoder. It uses the back inputs to the encoder, because of the added phase reversal the centre comes out in phase in the encoded output. The stereo signal is now converted to an SQ encoded one with left encoded as left back right encoded as right back while centre remains centre front.
 
Top