Gain Riding Logic - did it ever sound good?

[Sonik Wiz]

That would be incorrect, no logic at all in that SQD-1000. Correct that It would've maintained full left to right separation (no blend). That was always the strength of SQ! You guys must be thinking of a different model, with front to back logic.

True, that:

http://www.4channelsound.com/logic.htm

 

[Doug G.]

My SQD-2050s are front-back logic and sound very nice.

Doug

 

[par4ken]

Dealer - "Are you sure 3dB will be enough for customers to be wowed by quad?"

Company Rep. - "Oh heck yeah, It's easy to hear where things are with 3dB."

The Public - Shrug.

Although the separation was not great I was always wowed by the pseudo surround effect even on stereo records. That was the strength of all matrix systems even/especially without logic. It also was a teaser as to what full discrete would be like! We became spoiled by the high separation decoders. Going backward and listening to my homebrew Dyna style decoder, I'm still amazed by just how good such a simple decode can sound!

As far as wowing the public though, matrix quad at least was perhaps released too early before being perfected.

 

[kfbkfb]

https://www.quadraphonicquad.com/fo...-sqd-1000-sqa-200-decoders.32333/#post-625335
Sony SQ ad - mentions front-back logic.


Kirk Bayne

 

[jaybird100]

That would be incorrect, no logic at all in that SQD-1000. Correct that It would've maintained full left to right separation (no blend). That was always the strength of SQ! You guys must be thinking of a different model, with front to back logic.

The SQD-1000 had what they called "partial logic", which was, in fact, the gain-riding circuitry to try to enhance front to back separation. The effect was clearly, and painfully, audible. It didn't do SQ any favors, to be honest.

 

[Sonik Wiz]

In the question of SQ Full Logic sounding good, apparently it depends on what type of Full Logic. Disclord had something to say about this:

You need to separate the decoders into the Full-wave matching with Front/Back gain riding logic and the wave matching with F/B Vari-blend. The Lafayette SQ-W is a wave matching with Vari-blend unit and sounds much better than units like the Sony SQD-2020 that use wave matching and F/B gain riding logic. The Vari-blend truly cancels CF vocals and instruments from the rear channels while the F\B gain riding logic just lowers their level.

Read More here:
https://www.quadraphonicquad.com/forums/threads/list-of-sq-full-logic-units.17091/#post-189107

 

[par4ken]

I'm glad that this decoder was brought up here. Listening to it through the small speakers surrounding my workbench it seems to preform well. I was surprised that it includes "logic" but it appears to be more like vari-blend almost like vario-matrix. I hear no noticeable pumping.

Testing by generating test signals via Adobe Audition and measuring levels with my DVM I calculated over 22dB separation left to right across the rear. Checking level difference Cf to Cb my readings were between 8-9dB.

I picked this decoder up very cheaply years ago on eBay (back when you could still find bargains). I lent it to a friend who always runs double stereo but he was just too lazy to try it out! I eventually got it back and simply stored it away, not thinking about it until this tread. I'll have to listen to it on my main system to see how well it preforms there. Listening now to the back channels only and I don't notice that closed in sound of fixed blend.

I did a quick comparison with the Lafayette SQ-L listening to the back channels only and the Sony was more open, the Lafayette seems more like mono across the rear. The switches of the Lafayette do need cleaning badly. Listening only to the back channels of the Lafayette level pumping/shifting is noticeable.

Actual gain riding would've been necessary to increase left front to left back and right front to right back beyond 3dB. Gain riding comes with a price, that of audible pumping effects.
The SQD-1000 and SQA-200 do not use gain riding!

 

[Doug G.]

With my post about the public shrugging, I may have left the impression that I was one of the public. I was definitely not. I was a quad nut right off the bat with my Hafler set up and par4ken is exactly right. Even without separation that allows pinpoint localization of recorded elements, the added ambience and pseudo quad from regular two channel sources, makes quad superior to any two channel system, in spite of two channel enthusiasts who claim their systems are just as three dimensional as quadraphonics.

Doug

 

[kfbkfb]

The SQD-1000 and SQA-200 do not use gain riding!

I don't know how I got the idea that they did, perhaps a review of some sort said gain riding was used.

The Sony logic system must predate the CBS admonishment to not place content in CB for SQ encoding since these Sony SQ decoders will detect CB content and blend LF and RF to improve CF/CB separation.


Kirk Bayne

 

[tonyE]

Have you noticed that, all of a sudden, it's HER living room, not OUR living room? She has assumed full ownership of whatever room hubby wants to express himself.

You must be doing something wrong.

She jokingly recently described (our) living room like a rich bachelor's pad. One wall is loaded with a display of fine electronics and four speakers... I got stuff in front of the fireplace (only used once a year) and we have NO coffee table ( because it does screw up the soundstaging). She agrees that is sounds like music, not a stereo.

OTOH, the den is hers. The 77" LG OLED and a 7 channel HT are in there... open "concept" to the kitchen. I just do maintenance in there.

And I never forget our anniversary, mother's day, Valentine's day, her B-day, Christmas and I get her stuff all the time.

Wife happy, me happy... and, with all of this working from home, my "under the radar" expenses are now up to $700 and my "make up my own mind, don't need approval" is up to $1000... so I'm happy (she handles the bills).

 

[Doug G.]

Your wife is an "outlier". Lucky for you.



Doug

 

[tonyE]

Your wife is an "outlier". Lucky for you.



Doug

True... you ought to see her drive a stick shift and shift at redline while wearing 4 inch pumps... amazing.

She also always races me at the red light. I let her win.... shhhh... don't tell her.

Nice little lady.. sure, sure, to everybody but me. But, I must say it's a reasonable compromise and we like the same kind of music and movies so that works out fine in the end.

I ought to note, though, that when I crossed the $8K mark on getting amps built and vintage receivers rebuilt she finally said something. "But honey, I'm cleaning up the closet and I'm fixing the stuff I really want to keep"... Nevermind the DIY Pass Aleph 2s that are due chez nous sometime in June. Those 5U black beasts will be somewhat hard to hide ( I made my payments in monthly tranches so as to not shake up the tree too much, actually, I keep it under $1K per month at most )... and I'm almost done, for the time being, or I will be toast.

Yep, I am lucky in that respect.

BTW, wanna buy some stuff? I got some really nice NAD Monitor stuff...

 

[national-kid]

Reference information:
Measured values of various decoders.
http://www.hi-ho.ne.jp/odaka/quad/XT.pdf

 

[kfbkfb]

Reference information:

I can't help but notice the low frequency drop off below ~100Hz for both the Sansui and Surround Master decoders, the other decoders are basically flat to 20Hz, any idea why this is so?


Kirk Bayne

 

[ar surround]

Perhaps what's most interesting is that matrix encode quad remains fascinating to this day. It was fascinating to me back then and it is so now. Anyone can make a discrete recording, but matrix encoding/decoding is black magic.

 

[MidiMagic]

I don't know how I got the idea that they did, perhaps a review of some sort said gain riding was used.

The Sony logic system must predate the CBS admonishment to not place content in CB for SQ encoding since these Sony SQ decoders will detect CB content and blend LF and RF to improve CF/CB separation.

Kirk Bayne

The admonishment was to keep CB content from disappearing in mono play (including listening to a stereo station with a mono radio). Encoded CB works for all other SQ functions.

Perhaps what's most interesting is that matrix encode quad remains fascinating to this day. It was fascinating to me back then and it is so now. Anyone can make a discrete recording, but matrix encoding/decoding is black magic.

And I do it all the time with a 4-bus mixer and a simple passive encoder in the bus 3/4 inserts.

 

[gvl_guy]

The Sony SQD-1000 decoder, which was the first SQ decoder I bought, used gain riding to try to enhance separation, but the "pumping" effect was highly annoying. Sony referred to the method as "partial logic". It was a valiant first attempt, but when you see how far any matrix decoding has progressed (the Surround Master comes to mind), well, it makes me wonder what would have been had decoding at that level been available back in the early 70's.

I really believe if they had the technology like the Surround Master or Tate decoders back in the early to mid 1970's, the quad "wars" would have been over. There would have been no special pressings needed to make the vinyl records, no special cartridges, no special FCC authorization for FM broadcasts, nothing. Quad might not have "flourished," but it would not have died an embarrassing death with so many competing systems.

Future technology would have been affected, too. Would they have developed 5.1? Would regular CD's have a quad version? Would TV or FM HD radio automatically been developed with 4 channels in mind? Who knows?

 

[ar surround]

I really believe if they had the technology like the Surround Master or Tate decoders back in the early to mid 1970's, the quad "wars" would have been over. There would have been no special pressings needed to make the vinyl records, no special cartridges, no special FCC authorization for FM broadcasts, nothing. Quad might not have "flourished," but it would not have died an embarrassing death with so many competing systems.

Future technology would have been affected, too. Would they have developed 5.1? Would regular CD's have a quad version? Would TV or FM HD radio automatically been developed with 4 channels in mind? Who knows?

Happens all the time...Companies declare a technology as "commercial" too soon and their potential customers sour on it.

 

[gvl_guy]

Happens all the time...Companies declare a technology as "commercial" too soon and their potential customers sour on it.

Absolutely correct! How could anyone release a quadraphonic decoder with 3db of separation and think it's good? Greed.
And it was greed that caused all the different systems, too. That's why we had 33rpm and 45rpm, VHS and Beta, etc, etc. Eventually, one typically wins out, but in the case of quad, it was too many and too confusing.

 

[national-kid]

I can't help but notice the low frequency drop off below ~100Hz for both the Sansui and Surround Master decoders, the other decoders are basically flat to 20Hz, any idea why this is so?


Kirk Bayne

Perhaps the poor bass characteristics are
1) To avoid slowing down the logic response due to the large time constant when detecting the volume in the low frequency range.
2) By doing the above, in order to prevent the direction enhancement processing of the bass range by the direction detection result other than the bass range.
3) People have a dull sense of direction in the bass range, so it does not make much sense to detect the direction.
4) In vinyl, the bass range is recorded in monaural so that the needle does not fly, so there is not much point in detecting the direction.
5) Since the bass range has a large amplitude, we want to prevent it from becoming dominant in the detection of the sound source direction.
6) By distributing the bass range to the rear speakers, the amplitude of the diaphragm in the bass range is reduced so that even a small speaker can produce a loud sound. When played on speakers and spatially synthesized, it becomes roughly flat.

PS
In the QS decoding of the 3-band machine I made, I divided the band into 4 and decided not to apply logic to the lowest range.
Since the bass range is usually monaural recording, if you use the QS/SQ decoder, the bass will only sound in front. Therefore,
I wanted to make the best use of the four speaker woofers, so I made a bass distributor that distributes the bass range to all speakers. (Separately, I made the equipment for it)