Quadraphonic Adventures: 1990's Dynaco QD-2 Passive Surround Sound Device Tested.

April 2, 2018
#246

Gentle reader,

Firstly, thank you for taking the time to read my humble blog. It truly warms my heart that you do and thanks SO much for your comments and positive feedback. I had no inkling than anyone would read it, let alone that so MANY do! Thanks again.
My new-to-me QD-2. Could not remove the stains from the faceplate, despite trying numerous products. Not obvious when in place in the system.

 Proper and good quality banana plug terminals.
As you may know, I started getting into good stereo (and quadraphonic) equipment back around 1975-76. A friend had an amazing Pioneer 60 watts-per-channel stereo and I loved how it sounded so I wanted big clean sound too.

At first, I began reading Stereo Review, High Fidelity and Audio magazines. The reviews while well written, seemed to be all glowing endorsements. Then I saw an ad for a book by Mark Tobak titled: THE AUDIO ALTERNATIVE. I ordered it and once it arrived, dived in, reading about the various pieces of equipment he had tested and reviewed. Based upon his recommendations, I chose for my first system: Dynaco PAT-5 preamplifier kit, 2: SWTPC (SouthWest Technical Products Company) Tiger .01 60 watt mono power amplifiers, a pair of (floor model) Dynaco A-25 speakers and a B.I.C. 940 turntable with the optional walnut base and smoked dust cover. I do not recall what cartridge it came with. I bought each piece as I could afford it, starting with the PAT-5 kit. I’d never soldered before, but Dynaco’s instructions were excellent. Good thing I had that experience since the SWTPC kits were harder to do.
Above is a recent PAT-5 that had I bought and a stereo (lower powered) version of the Tiger mono amps. I wrote about these in an earlier article.
 
First, a little history on quadraphonic surround sound so that you will better understand what I’m talking about:

Quadraphonic music reproduction was introduced around 1968, or so. It was a new idea to increase the realism of home music listening by adding a pair of speakers behind the listeners. Many methods were developed, but there was only one DISCRETE form or quad music which most people could afford, and that was 8-track tape cartridges. 8-track tapes had four stereo tracks of music on a 1/4" wide tape that ran at 3 3/4 inches-per-second on a continuous loop of tape. Think of a super-highway eight lanes wide. The tape player’s head (which the tape moved across while playing) moved up or down every time a piece of silver tape (that joined the two ends) passed by the head. So, the tape head’s movement switched to the songs on the next two tracks. After all four “sides” had been played, it started at the first song again. With quadraphonic tapes there were TWO four-channel tracks side-by-side on the tape and the head played all four continuously, first side one, then the head moved up or down to the four channel tracks that comprised the second side of the music recorded on it. The tape itself had to be twice as long with a quad version of the same recording than the stereo version used. Thus, true and unique music could be placed on each of the four tracks to make up the “surround” music. Before I began building my first stereo, I bought a cheap quad system made by Electrophonic. It was an AM/FM Stereo receiver with built-in quadraphonic 8-track player and inputs for a turntable. It came with four cheap speakers. I bought only one quad tape: Blood, Sweat & Tears was the band, I don’t remember which record it was. It was a neat effect, one did seem to be right on stage with the band. If the unit had any quad decoding circuits, I do not recall.

Now, LP records, have a “V” shaped groove, each side of the groove holds one channel of music, which produces stereo sound. Electronics companies and record labels collaborated  on coming up with a way to get four channels of music from only two sides of the groove in the records. What systems they created were encoded systems. Each worked differently. They were called: QS, SQ and CD-4. QS was developed by Sansui and it was later the basis for Dolby Labs creation of Surround Sound for home theater movie systems, which at that time was either VHS video tape or Sony’s Betamax tape. Years later I found a huge and heavy Sansui quad receiver at a thrift store and it decoded VHS surround sound tapes perfectly. If you wish to learn more about quadraphonic sound, here is a link: 
Quadraphonic sound - Wikipedia
Dynaco's founder, David Hafler, figured out a way to extract “ambient” music and some of the sound of the space where the music was recorded with a passive-matrix circuit. In other words, no electricity was needed for their device to work. They called their creation that did this magic: Quadapter. That device’s model number was: QD-1. It matched the faces of their preamplifiers and integrated amplifiers they were producing, such as the PAT-5 above.

Sadly, the original Dynaco company went out of business. Another company based in Taiwan, the Pan-Orient Company, Panor for short, bought the rights in the late 1980's to the Dynaco name and set out to update some classic Dynaco tube products and create new, audiophile quality tube and solid state equipment as well. Since quadraphonic had faded away and analog and digital systems were in wide use by consumers with “home theaters” they decided to update the QD-1 of yore with a new look so that consumers could enjoy surround sound in home theaters without the expensive receivers and all the associated algorithm circuits and complications normally needed. All at a bargain price. They named it: QD-1 Series II.
I had enlarged the terminal holes to accept banana plugs.
I have owned a couple of the Panor-era Dynaco QD-1 Series II passive surround sound units over the years and they worked well. They had successfully added a center channel to them. My only complaint was they came with cheap plastic spring-terminals for the many speaker cables. They provide very little surface area contact for the sound signal. The first one I had, (above) I drilled the terminals to accept banana plugs. I passed it on to a new owner. A couple of years later, I bought another one. It was Series IIL. That one I replaced all the cheap connectors with double banana plug terminals. It was ugly, but it worked. Then I sold that one on as well.

NOW, THE DYNACO QD-2 FIVE CHANNEL SURROUND SOUND SYSTEM.
There have been many test records put out by various concerns over the decades. I have collected a number of them. Last weekend we visited a thrift store and they had a copy from the 1970's of Dynaco “4-Dimensional STEREO DEMONSTRATION DISC”. It was in great shape, too. So I bought it.

Looking at it later, I realized that I once again needed a Dynaco QD device to fully appreciate what the record was designed to showcase. A look on eBay, and to my surprise, there was a QD-2 available! The QD-2 has what the QD-1 models lacked: Proper 3/4" spaced 3-way banana/binding posts. 14 of them. The price was reasonable and it arrived yesterday.

Unlike the QD-1 Series II models, the QD-2 sported a mirror-finish faceplate verses the plain black painted metal of it's predecessors. However, no matter what I used to clean it, I could not get it spotless.
 
There are three control knobs which mimic the earlier models. I believe the internal circuits and controls are unchanged, but do not know for sure.
Dynaco QD1 review
I heard a rattle when I picked up the QD-2 and since I always open new electronics to see what’s inside, I did this time as well. I found the two screws that hold the circuit board down were missing. A search of my metric fasteners drawer yielded two screws perfect for the task. I used DeToxit spray on the two controls on each side, but the huge gain control which is three attenuation controls stacked, one for the center and two for the rear/surround speakers will not allow internal cleaning.
The minor resistance seen (on my digital multimeter) prior to cleaning the controls was gone. It was essentially, the proverbial: Strait wire, with gain. Except it doesn’t actually gain. Despite what the knob states. Oh, it get's louder, but that device merely attenuates the music coming from the center and surround speakers.

I have owned a number of different types and brands of speaker cables all of which I have reviewed in these articles. One kind that I bought a 100 foot roll of is ten gauge, twisted pair. One conductor seems to be silver and the other copper. The latter wears translucent blue insulation, the former, clear. Both are enclosed in thick-clear plastic tubing. I like the way it sounds and still use it in many projects. Since I had so much, I chose it for the rear speakers and the Dynaco A25XL units as the speakers. The cabling can be seen in photos further below in the article.
  The QD-2 "in situ", terminals plugged and ready for business.
 Klipsch KD-2 right front above, left front below.

 A25XL right surround above, left surround below.

Since I was moving the speakers, I took the time to carefully sand the walnut veneer and apply boiled linseed oil to all the surfaces. They turned out very well. I also applied the oil to my Klipsch KG-4 speakers which would now be the main/front speakers. What a difference in the looks. Since my youngest grandson started pushing on the woofer of one of my speakers, I have put all the grilles back on. No difference in sound and they do look better. As far as I can tell, the black cloth is from the Danish company that built them oh so long ago.
At first, I angled the A25XLs a bit towards my listening chair, which is a very old wingback chair that also reclines. I love that chair, but it is looking threadbare in places.  
Then, I decided to place them facing the chair. The wings do get in the way in this situation, but by switching to just the surrounds, music is clearly heard. I tried the Dynaco LP first and was not disappointed! I have one from Fisher that is quad encoded and also have a lot of quad LPs of various genres. 
Above and below shows the system with the QD-2 in place between my Dynaco ST-200 power amp and PROTON 1100 preamp.

Overall, I really like the experience. The soundstage seems to have opened up and I do feel that I am sitting near-field because the music truly is surrounding me. I am excited to try many different recordings (I have over 3000!) to see how they sound, especially the quad LPs. 
 The flash really lightens the poor-old-chair's coloring.
    The front of the room with bonsai and dragons rearranged.
Online reviews of these Panor-era Dynaco QD-1 Series II and QD-2s are all very positive with some stating they will "never go back to plain stereo". That is quite a convincing statement! These units are often available on eBay, although the QD-2s are quite rare. Pure happenstance it was there when I needed one.
Thanks for taking the time to read this long tome! Next chapter will be about all the test records and CDs that I have in my collection.

Scott

April 2, 2018

Review of AIYIMA T2 6K4 Tube Preamplifier Can this Solid Little Asian Beauty Sing?

  March 20, 2024 #477 Gentle reader, This video takes over from the previous one here:  The Robb Collections: UPDATE Inexpensive Chinese-Mad...