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SQ Decoder: CBS SQL-200

Wagonmaster_91

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I haven't posted in this section before, so I thought I would share a few items I have. This is the CBS Technology Center "Full Logic Decoder and Stereo Enhancer SQL-200".
IMG_0018.JPG

This early 70's unit is very rare. I have only seen it mentioned in one thread on this forum:
https://www.quadraphonicquad.com/forums/showthread.php?3416-How-does-this-decoder-compare&highlight=CBS+SQL-200

The front panel has a volume control/on-off, front channels balance, Front/Back balance, back channels balance, Dimension (I believe for the Stereo Enhance function, probably a variable Hafler circuit for the rear channels) and SQ/Stereo Enhance/Stereo function selector. The case is metal with a brushed aluminum and 'wood grain' top, sides and bottom.
IMG_0017.JPG IMG_0024.JPG

Note that on the back the serial number on this particular unit is #26.
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It's very simple inside with a single circuit board layout.
IMG_0052.JPGIMG_0053.JPG

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I don't use this in my system since I have a Tate, Lafayettes and other decoders, but it is an interesting rarity. Hope you enjoy the pics. I have some other units you don't see very often I will upload soon.

Mark
 

eyg2181

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Thank you for the contribution. Everything is appreciated, interesting unit as well. I know you said you don't use it, but have you ever had it hooked up, just to see how it sounded?
 

Disclord

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The Dimension control adjusts the amount of logic enhancement applied to the 'corner' signals, from full logic down to -3db separation - it leaves the Front/Back Logic fully active. Some SQ LP's, particularly super reverberant ones, cause unstable logic under full 'action' and by reducing the separation, a more smooth soundfield is produced.

It's too bad CBS based the unit on the Motorola chips - the SQ IC has cheesy 4-pole phase shifters with something like 22 degrees of phase error. Plus it doesn't sound too good.
 

Wagonmaster_91

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Replying to eyg2181: Yes, just to test it out. Maybe I'm spoiled by my other decoders, but I wasn't too impressed. It has decent front to back separation but the rear channels do not seem to have much separation. I do not see any way to 'tune' it either. As you can see by the photos there are only two variable pots on the circuit board and I believe both are in the power supply circuit (not the decoding circuit). I think all the decoding was via the ICs. Personally I think the later SQD-2020 and SQD-2010 units do a better job. Still, the SQL-200 (and 400) are so rare it is just cool to have one that looks brand new to examine.
 
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Wagonmaster_91

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Disclord, your comment about the Dimension control prompted me to do a bit more testing. To be honest I can't tell it is doing much in the SQ position, but in the Stereo Enhance mode I can now definitely tell a difference. Turned fully clockwise, sounds in the hard right or hard left stereo channels 'jump' prominently out of the rear channels. Turning The Dimension control lessens that effect. In a larger room this can be a cool effect on some material.
One thing I did discover that I have never found on any other quad decoder (including the Tate, Lafayettes, EVs or Sansui QSDs) is that the Stereo Enhance mode effects all four channels, not just the rear ones. (Anyone on the board care to comment on that statement? Do you know of a quad synth that alters the front L&R channels?)
So, while I am not impressed with this unit's SQ decoding, the Stereo Enhance mode is interesting and seems to be unique.
 

Disclord

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Disclord, your comment about the Dimension control prompted me to do a bit more testing. To be honest I can't tell it is doing much in the SQ position, but in the Stereo Enhance mode I can now definitely tell a difference. Turned fully clockwise, sounds in the hard right or hard left stereo channels 'jump' prominently out of the rear channels. Turning The Dimension control lessens that effect. In a larger room this can be a cool effect on some material.
One thing I did discover that I have never found on any other quad decoder (including the Tate, Lafayettes, EVs or Sansui QSDs) is that the Stereo Enhance mode effects all four channels, not just the rear ones. (Anyone on the board care to comment on that statement? Do you know of a quad synth that alters the front L&R channels?)
So, while I am not impressed with this unit's SQ decoding, the Stereo Enhance mode is interesting and seems to be unique.
With the 270 degree stereo surround synthesis the SQL uses, as the logic is turned 'down' via the Dimension control, the front L & R will get more and more of the back, giving the effect of the rears moving to the front. As it's moved to the higher, more logic, position, the rears will become more prominent as the fronts are reduced in level with the logic action. So the dimension control is doing what it should - try it with a super quaddy SQ album like Chase Open Up Wide - the trumpets locations should be more blurred as the dimension is turned down.

The Audionics Space & Image Composer had a stereo enhance control that allowed you to vary the amount of the effect, from, basically, stereo with ambience, to full, 270 surround, that pulled the sound around in a horseshoe with full DES enhancement, which is what most quad synthesis did. The Fosgate Tate 101A used the 270 mode for stereo surround synthesis too, but had no way of varying the effect. The Fosgate Tate is also the the only Tate DES-based decoder that had the Automatic Dimension Control that Martin Willcocks patented - it gave optimal placement for all source positions in a 360 circle and varied the amount and speed of logic action automatically for optimal decoding of almost all SQ recordings. The Audionics was much slower and pretty much didn't decode the side positions - only the front and back quadrants.

BTW, try playing an SQ encoded album in the stereo enhance mode - it pulls the rear channels to the front and flips them, left for right, while the fronts are pulled to the rear, with Center Front staying center front. Dan Gravereaux called it a "pretzel" effect and it looks really crazy on the Energy Sphere (Scheiber Sphere).

The CBS Paramatrix decoder for SQ also had a manual dimension control, similar to the SQL, and worked the same way - full corner logic off variable to full on, with CF/CB logic staying fully active.
 

Disclord

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I forgot to thank you for posting the pics of the SQL-200.

One thing about CBS made gear is that it's BEAUTIFUL, with all the brushed aluminum. And the circuit boards are great looking too. Since the SQL-200 used the standard Motorola full-logic chip set, the SQL-200, as a CBS design, would have to be the 'reference' as to how this design should sound. Sadly, and unlike, say Dolby Labs today, CBS enforced NO STANDARDS for SQ Logic action and the $6000 SQ license fee - either in how the logic determined channel dominance or the time-constants and overall effect. As an example, the Sony SQD-2020 handles the wave matching in a different way than the Lafayette SQ-W, and the time constants are very different between the two units... the SQ-W is simpler than the Sony but also faster giving a better quad effect - and both are way faster than the Motorola IC design. And better sounding in basic Hi-Fi, with much more accurate phase shifts and thus, better SQ performance.

Can you post some pics of the SQL-400?
 

Wagonmaster_91

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Sorry, but I don't have a 400 and have never seen one. Hopefully someone else on the board here has one and will post some pics.
 

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I have a SQL-400 and it is identical to the SQL-200 appearance-wise. It delivers the best SQ separation of all my decoders.
 

Bluvic

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I just found the manual on it with all the specs and schematics. Digging through a lot of my old quad stuff. I kept my LPs so I still have a thousand of those.
 

jefe1

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Unfortunately you are replying to a dead man. Disclord would have loved to look at the manual and ask you questions. He was a treasure trove of knowledge around here.
 
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Yes, Disclord was a wealth of knowledge, and thanks to the forum surviving, still is.

Bluvic, some of us may still be interested to see some pictures of the SQL-400, even though it may be a look-a-like to the SQL-200. I wonder what the improvements were to the design with the -400 model?
I don't remember having read this thread originally, and don't recall coming across either model on on-line auctions.
 

Soundfield

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I just found the manual on it with all the specs and schematics. Digging through a lot of my old quad stuff. I kept my LPs so I still have a thousand of those.
Hi Bluvic, it would be really interesting if you could share the SQL-400 manual or at least the circuit diagram. Cheers.
 
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Sonik Wiz

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Hi Bluvic!

I'm with Nite1922:
Hi Bluvic, it would be really interesting if you could share the SQL-400 manual or at least the circuit diagram. Cheers.
If you have the chance to scan & share it would be most appreciated!
 

Soundfield

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Hi Bluvic!

I'm with Nite1922:

If you have the chance to scan & share it would be most appreciated!
Sadly Sonik I suspect our entreaties are falling on deaf ears as Bluvic's profile says "Last seen Sep 18, 2018 "!!
 
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