Dynaco Quad

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dr8track

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Not sure if this question belongs in the SQ or CD-4 section. Is anyone familiar with Dynaco quad LP's? What do you need to decode them? How discrete are these recordings? There's an interesting quad LP and the seller says it's labeled as Dynaco quad.
 

Marcsten

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Not sure exactly which disc you are referring to here, but if its what I think is meant, there were some VERY early discs on Dynaquad which are, I beelieve, about like EV-4, which is a very early matrix system similar but not quite the same as qs. I would run it through a qs decoder. Dynaco became most well known later for the out of phase (oop) decoder fro synthesizing quad from stereo. This is not the same thing.
Marc
 

Cai Campbell

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Dynaco was very early on the quad scene with their "Quadaptor". This was a simple ambience recovery circuit. I believe this was a direct adaptation of the infamous Halfler circuit.

I don't believe there was ever a Dynaco encoder or anything ever developed, but some recordings were specifically mixed/recorded to take maximum advantage of the Halfler effect. A couple of the Beach Boys records were among them ("Sunflower" and part of "Surfs Up").

The only "true" Dynaco decoders I've seen are amplified signal decoders. In other words, they take the amplified output of a stereo receiver and connect directly to four speakers. Since this is totally out-of-whack with everything else in my system, I've never actually hooked one up.

In any event, the so-called Dynaco quad LP's I've listened to decode quite nicely through any matrix decoder.

EV-4 or ElectroVoice 4-channel was another early player in the quad scene, and I believe it was the first commercially available matrix quad format (being truly encoded as opposed to derived). I owned an EV decoder for a while but found that EV encoded disks played through it offered exceptionally minimal separation and quad effect. These pioneering efforts are much better served through the more advanced matrix decoders such as the QSD-1 or the Tate.
 

Scottmoose

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They work OK through QS or SQ logic. Not great, but OK. To get a feel for how it sounded when new, fire it through a passive Hafler circuit. Well, sort of. If memory serves, Dynaco did a wierd version / varient on Hafler, that you can recreate like this: Normal front stereo speakers, as per usual. Two rears: wire the positives on the amp to the negatives on the rear speakers, the the positive rear speaker terminals together, so it's hooked up in series, but out of phase. Standard Hafler / ambiophonic stuff; no change there. We all know it works quite nicely, and is a great improvement on normal two speaker stereo (Well, I thinks so. I know some people deride it as inaccurate, but I'd suggest the reverse -at least the reverb and echo is where it belongs!)
Next, bridge the negative terminals on the amp (I'd use a second set of speaker terminals for the rears if possible), and attach the bridge to an 8ohm resistor. The other end of this, attach at any point to the bridge between the two positive rear speaker terminals. Oh, and add a pot for each rear speaker whilst you're at it. This'll give you a right rear channel with 75% of the right front, and 25% of the left front, and visa versa for the left rear. And that's it. It sort of works. But I reckon of all the passive matrix decoding, a normal, out of phase Hafler setup is the best. I still use it on my second system.
Scott
 
D

Dreadstar

Guest
Not sure exactly which disc you are referring to here, but if its what I think is meant, there were some VERY early discs on Dynaquad which are, I beelieve, about like EV-4, which is a very early matrix system similar but not quite the same as qs. I would run it through a qs decoder. Dynaco became most well known later for the out of phase (oop) decoder fro synthesizing quad from stereo. This is not the same thing.
Marc
The Dynaco passive decoder is calculated expressly to decode the Dynaco discs, it's an actual decoder not just an ambience extractor. There's a misconception that the front speakers play the whole composite left and right channels but it overlooks that the rear speakers across the two 'hot' terminals with practically no ground connection of their own actually function as blend resistors across the front channels, canceling a proportionate part of the rear channels from the front channels. This is exactly equivalent to the way SQ non-logic decoders and EV decoders use blend resistors to increase front-to-back separation at the expense of left-to-right separation. EV and Dynaco are the only two that can locate a sound at dead-center left or right using the four-corners speaker placement. If SQ and QS try it the front and rear volume on that side will be equal, but 90% out of phase, which simply does not work. I'm suspecting that this is why those users prefer their rear speakers to their sides instead. One issue presents itself when you realize Dynaco's adapter is a real decoder though, if you use resistive volume controls as Dynaco does, you are actually imbalancing the decoding coefficients everytime you adjust them. To make a 'super' passive decoder you would replace those with 8 ohm L-Pads which present the same 8 ohm load regardless of speaker volume.
 

Feirstein

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As a "kid" I did some work in NYC for Dynaco. The best way to use this concept, in my opinion, is to merely take the passive approach. Wire a single or pair of rear speakers to the front speakers with wire only. The positive of the left to the positive of the left rear, the positive of the right to the positive of the right rear, and the two negative posts on the rear speakers wired together. Put on the first LP mix of the Boxer by S&G and you will be blown away with what a mere 3dB of seperation can do for the sonic field.

I still have my Dynaco issued demo LP which includes this hookup suggestion. The little passive boxes Dynaco sold had a variable resister on the ground side of the hookup to control rear level. I tried this with some success in several of my vehicles but found that the changes in stereo seperation with reception quality was a fly in the ointment, so to speak. I think it worked better that some of the complex decoding systems we have experienced over the years, and it introduces no noise or distortion of its own into the mix.

Richard
 
D

Dreadstar

Guest
As a "kid" I did some work in NYC for Dynaco. The best way to use this concept, in my opinion, is to merely take the passive approach. Wire a single or pair of rear speakers to the front speakers with wire only. The positive of the left to the positive of the left rear, the positive of the right to the positive of the right rear, and the two negative posts on the rear speakers wired together.
<snip>
The little passive boxes Dynaco sold had a variable resister on the ground side of the hookup to control rear level. I tried this with some success in several of my vehicles but found that the changes in stereo seperation with reception quality was a fly in the ointment, so to speak. I think it worked better that some of the complex decoding systems we have experienced over the years, and it introduces no noise or distortion of its own into the mix.

Richard

Wow I completely agree with you. The interesting thing about two rear speakers hooked up that way is that the left rear and right rear are in phase with the front speakers on their sides, but out of phase with each other. So as a sound moves off-center it wraps to the side, and every bit of leakage to the opposite rear channel is completely out of phase, so there is acoustic cancellation. Center front has TOTAL separation from center rear at all times WITHOUT artificial logic steering, and dead-center rear stays in the rear because the psychoacoustic effect of 180 degree out of phase signals in front is to feel vaguely to the rear, and can be cancelled from the front further by minimal front blending. It will be out of phase and blurred in back too, but the point is it will stay in back where it belongs. If recording engineers thought in terms of left front-center front-right front and a diffused rear, then it would be ideal. Ironically the actual 'diamond' layout is worse for reproducing that diamond pattern, because a single rear speaker will be in phase with one front channel but out of phase with the other.

So let's say you design a new decoder, one that treats stereo as an actual quad matrix. The artist or engineer still thinks in terms of a left-to-right stereo spread, except it will bend around the listener that has a passive adapter, and a seperate rear sound position is a possible extra bonus. And although there is really only a single dead-center rear channel, it can generate it's left-or-right directionality by choosing which front speaker it's in phase with, by choosing if it's encoded as (+L-R) or (+R-L).

You have alot more separation to work with if you only derive 3 channels out of stereo mathematically like this instead of 4, and harness psychoacoustics for the minimal rear separation that's needed for 4 apparent channels.

My last voyage into passive quad 10 years ago I tried both the four-corners and the Wendy Carlos speaker placements, and each had songs they were better suited to. And I don't mean just slightly better, I mean profoundly and absolutely, making the difference of whether a 3D soundstage was percieved or not.

So I dunno, either you plan for 6 speakers, or you use four corners and have a setting that wraps dead center left (and right) equally between the side speakers instead of the "horseshoe" wrap, in other words dead-center left appears midway between front left and back left instead of wrapping all the way to left rear. I look at the distribution patterns of SQ and QS and I see that *neither one* can place a sound dead-center-left (or right) in-phase, only pure amplitude matrixes like EV and Dynaco can do that. I'm not sure how QS got away with calling itself "regular matrix" and calling SQ "phase matrix" since both are equally phase matrixes and neither regular in any way.

Way back in high school the complaint I heard about quad was that it sounded "too spacey". I even knew a guy that got a cheap-o quad system for his birthday, and sold his two rear speakers because he didn't like it. I believe this is because of all the weird random phase angles, and wanting to listen AT something with a clear location instead of being immersed in it.

This is just my opinion but I think quad should have concentrated on making the front soundstage 3D instead of trying to place you in the center of the band. I think my current interest is to distribute a normal stereo signal among four speakers arranged in a 180 degree arc, and then two speakers in back for the out-of-phase sounds. It would probably work great for any quad or Dolby you run through it.

The only thing about passive matrixes is the L-R sounds have a hissy, spitty quality in the highs. I suspect this would not be the case if sounds were deliberately placed there by recording engineers instead of random ambient noise being extracted and reproduced. But that's what first generation Dolby did, deliberate L-R for the rear, so I'm eager to try.
 

Obbop

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http://praff.blogspot.com/2006_07_01_archive.html

Brian Eno had an LP out in the early 1980s that had a diagram on how to hook the speakers up for the OOPs effect (out of phase stereo).

The last reference I have seen for that very basic surround sound effect.

I have seen several different schematics over the years, some requiring resistors and potentiometers etc etc to obtain the "ultimate" in OOPs.

I betcha a "deep" Web search will find some of those.

Similar pre-made units were available even just a few years ago, advertised as a way to obtain faux surround sound from your VHS. I believe those units sold for $29 bucks or so and were no different from the "fancy" OOPs devices of the past, both self-made and store-bought.

Basically, I believe that any "decoder" you run across without a power cord is an OOPs unit!!!!

My limited experience with those things is that they are ineffective. Maybe folks with better ears than mine can hear results. I listened to a couple manufactured OOPs units years ago and was not impressed.

http://music.hyperreal.org/artists/brian_eno/onland-txt.html

Do a Google with "out of phase stereo" and a lot of stuff appears.

http://www.amsky.com/~cirkuit/media/surround.html

http://sound.westhost.com/project18.htm

Those are a few of the many Web sites with info and schematics.

Perhaps it is possible that one of those "advanced" schematics with a bunch of components working on the signal may provide a decent sound!!!!
 
D

Dreadstar

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Hey, thanks for the links! I am determined to build at least one new type decoder, and I think I can extrapolate what I need from links I followed from the links you posted.
 

tejanoboy

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I look at the distribution patterns of SQ and QS and I see that *neither one* can place a sound dead-center-left (or right) in-phase, only pure amplitude matrixes like EV and Dynaco can do that. I'm not sure how QS got away with calling itself "regular matrix" and calling SQ "phase matrix" since both are equally phase matrixes and neither regular in any way.

OK, I know it's an old post by an ex-member, but there are a few things that I feel the need to point out, in defense of the QS system:

Yes, a sound CAN be put precisely in center left or center right! The Sansui VM decoders included a pair of phase-shifters at the end of the process that restore the original phasing, so ALL speakers are back in phase.
Look at the description of this at "classicsansui.net", they have excellent copies of the original brochures from the QRX-series receivers, and this is detailed, along with a cool chart of stylus motion for all the different positions. (THAT makes a lot of sense, too!)
And SQ IS very much a "phase matrix", as the rear channels are identified only by phase, NOT amplitude differences. Look at the SQ formula, a sound in a single rear channel appears as an EQUAL signal in both Lt and Rt, but 90 degrees out of phase. Look at it on a 'scope, and it will draw a circle...just as the cutting stylus does when putting SQ on vinyl. "Phase matrix" is a fair name for this.
QS is called a "regular matrix" because it is just that, a totally symmetrical matrix that distributes the energy and separation evenly around the circle.
(Sansui called it a "square matrix", maybe that is a better term than "regular"?)
It uses the same formula Peter Schieber worked out, to wit
Lt=.92 Lf+.38 Rf+.92 Lb-.38 Rb, and one of the patents I've seen describes this AS IS as "regular matrix", and a Japanese standard. Seems Ms. Carlos hit it square on, RM + phase shifts = QS.
Looking at all the different matrix formulae, I grow ever more convinced that QS made the most sense, and had QRX receivers or any other VM decoding gear come out five years sooner than they did, QS may well have become a single global standard for ALL matrix quad.
I imagine you owners of Sansui's finest will testify that the sound field is quite realistic, no?
Just my own observations, but I feel them strongly enough to want to find a working QRX-anything very soon! :>)
TB
 

MidiMagic

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"Regular Matrix" is a specific type of square matrix in linear algebra. If raised to a high enough power, all entries are positive.

"Square Matrix" is any matrix with the same number of rows and columns.

By the way, the linear algebra matrix is used to calculate the quadraphonic matrix.
 
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