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August 1999
Enjoy the Music.com Review Magazine
Dynaco QD-1/IIL...a Decoder Cheap?
Article by Bruce Kinch
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  PSST! Hey, Buddy-

  Wanna Buy a Decoder?

Home Theater, the mid-fi monster eating at the heart the audiophile way, seems to be winning converts on every front, and music lovers everywhere are being plunged into darkness in the name of domestic tranquility, microwave popcorn, and a better bottom line-subwoofer sales are up, up, up! You’ve heard the rumors. God is Dead, although I also hear (s)he’s coming back. Paul is Dead. The LP is Dead. Stereo is dead. Trust me, you just can’t believe all those rumors. After all, what's deader than Quad?

Surprise!! Quad, a technology long assumed a victim of corporate format wars of the '70s, survives today as Dolby Surround, which like its second generation, Dolby Pro Logic, is built on principles derived from the SQ and QS matrix encoding techniques employed on many of the best LPs ever recorded. Only the names have been changed to protect the retailers. Today, Quad is what? A muscle? Part of a college campus?

Quad never went mainstream back then, mostly because mom wouldn’t dream of letting dad put two more of those huge hideous wooden boxes in her living room just to listen to Pink Floyd at 105 dB. Twenty-five years later, mirabile dictu, young couples shop together at Circuit City for an appliance called Home Theater, one really big TV and 5.1 of the cutest little speakers. (Honey, they can even install them inside the walls!) She gets movies, he gets the Super Bowl, and the kids SAT’s continue to decline. Dolby has made surround sound the American Way. What a country!

So yes, you can use a Home Theater rig to play those quad records moldering in the basement, although I would hardly recommend buying an "AV receiver" for serious audiophile use. The majority of Home Theater components, DSP processing, and speaker set-ups just can't recreate the "soundstage" that is the most seductive part of purist stereo. On the other hand, no stereo playback can immerse the listener in a "sound-field" the way a surround system can. By that I mean recreating the ambience of the recording space, whether it be a concert hall, jazz club, rock arena, or studio–as the listener's acoustic environment. The sense of "being there", rather than hearing the musicians through a perceptual window at the front of the listening room. Something entirely different from having "discrete" sound sources arbitrarily located around your head–which is what Home Theatre–and Quad–were designed to do, most irritatingly so in many cases.

In its simplest form, stereo requires two microphones arranged to pick-up differing versions of a recorded sound–slight variations of loudness (or amplitude) and arrival time (or phase). For a direct sound from an instrument or voice, the differences are stable (i.e., in phase) and a stereo image is created in playback. But indirect sound, bounced off the room boundaries, arrives at the mikes completely out of phase, and we hear this as ambience-the "sound" of the room. If only we could isolate this out-of-phase ambience, and redirect it to a couple of speakers in the back of the room, we'd have the best of stereo and surround sound combined!

Guess what? It's easier done than said, and costs next to nothing. For this we must thank the legendary David Hafler, founder of Dynaco, and the patron saint of budget conscious audiophiles since the 1950s. Hafler devised a simple way to extract ambience by connecting rear speakers to the + terminals of the front speakers: the famous Hafler Hookup. The result was the stereo difference (or L-R) signal, which was primarily ambience, coming from the rear speakers, greatly enhancing the recreation of spatial effects. Dynaco later marketed a $30 box that simplified the connections, the Quadapter. Introduced to enhance plain stereo recordings, the Hafler approach was in fact the precursor of what we today call SQ/QS Quad and Dolby surround matrixes; these are just schemes to purposely encode (and "steer") specific out-of-phase information to create more dramatic effects than mere ambience recovery. As a result, the very retro Hafler Hookup does a decent–and quite benign–job of decoding the later processes. I imagine more audiophiles would explore passive ambience extraction if the manufacturers could figure out how to charge a lot for what is basically free-you don't even need an amp for the back channels. Actually, some have tried–recently Audio Research marketed a passive surround system, some $3000 worth, including a digital delay to increase the spatial impressions, but no Dolby circuitry. Speaker manufacturer Richard Vandersteen, who knows a thing or two about imaging and surround sound, enjoys one in his personal system.

QD-1/IIL FrontBut guess what, sports fans? We’re here to say you can buy a BRAND-NEW-IN-THE-BOX QUAD/STEREO/HOME THEATER DECODER FOR LESS THAN $20!! And who would you think we can thank for such a deal? Audio’s same old bang-for-the-buck champion: Dynaco, as partially resuscitated by the Panor Corp. They had some success updating the classic Dyna tube gear, and made quite decent tube-based CD players. When home theater started to attract the VCR rental market, somebody had the cool idea to modify the ‘70s Quadaptor version of the Hafler circuit for video surround use. The result was the QD-1/IIL, a modern iteration of the passive, speaker-level, out-of-phase-ambience extractor. It’s no more a Dolby decoder than the original was designed for SQ, but like its ancestor, the QD-1/IIL works on both stereo and quad LPs, CDs, tape and FM as well as movies–all without digital signal processing, phase-shifting anomalies, added noise or other nasty side effects.

QD-1/IIL Inside ViewNot only that, it has several enhancements that make it even better for audio use than the original. Because the QD-1/IIL has an impedance balancing circuit, you don’t even have to run the front speakers through it–the amp never sees less than 4 ohms. Or you can use a second amp and dedicate it to the QD-1/IIL, and keep the front totally unaffected. Early-jazz fans will delight in its ability to derive a center channel for those hole-in-the middle Van Gelders. There’s even a HF contour switch to roll off the rear–oops, sorry, we call ‘em surround now–speakers. Just the trick to keep noisy LP pressings from buzzing around your head. All you need is some zip cord and a couple inexpensive speakers, preferably a bit more efficient that the front pair so you can better adjust the balance with the QD-1/IIL’s attenuator, and you are in business.

The QD-1/IIL is a well-made little box (about the size of the Audio Alchemy stuff), and it retailed at a very reasonable $90. I remember quite complimentary reviews of it in the audio/video mags. Imagine my surprise when I saw the little devil advertised on the back page of the New York Times’ Arts section…for would-ya-believe $19.95. We are talking close-out countdown here, so get cracking–I presume J and R Music World bought up the remaining stock. Naturally, I ordered one up, and strapped it into the system. Nothing fancy, some Radio Shack 18ga. and my old Spica TC-50s some 6 feet behind the couch. (I aimed them at the sidewalls to fully diffuse the ambient sound–you might try box speakers aimed up at the ceiling. Great reason to buy Bose at the next yard sale, too). I set the gain so the rear speakers were not quite audible as independent sources.

The results were interesting in the extreme, although varied from record to record, genre to genre. As expected, SQ/QS recordings came through beautifully, although with somewhat less "localization " than I’ve heard from active matrix decoders. What was most satisfying was the degree of enhancement on many (but not all) straight stereo LPs and CDs. What worked best? Minimally miked classical (Decca, EMI, Mercury, RCA etc.) acquired a sublime sense of "being in the hall" that simply eclipsed 2-channel replay–immersion in the ambient soundfield really opens up the stereo imaging, particularly the sense of depth. Same with live recordings in general–Dan Hicks’ Where’s the Money awoke aural memories of hanging out at the Troubador as never before. Sound tracks "designed" for cinema surround were a big success–things like Glory, The Emerald Forest, Ry Cooder’s "ambient" guitar work on Alamo Bay and Paris, Texas. Jazz recordings were more variable, but ensemble and staging was usually more coherent. Live FM was fabulous. What didn’t work? Multi-tracked, overdubbed anything was usually no better, sometimes plain odd; in-studio processing, I presume. Bottom Line? The QD-1/IIL has got to be the most amazing $20 little black box you’ll ever add to a stereo system! Get 'em while you can, and enjoy some ambience with the music.

Tonality 80
Sub-bass (10 Hz - 60 Hz) 25
Mid-bass (60 Hz - 200 Hz) 50-75
Midrange (200 Hz - 3,000 Hz) 85
High-frequencies (3,000 Hz on up) 50-75
Attack 50
Decay 90
Inner Resolution 50
Soundscape width front 90
Soundscape width rear 90
Soundscape depth behind speakers 95
Soundscape extension into the room 95
Imaging 85
Fit and Finish 80
Self Noise 100
Value for the Money 95



J and R Music World
Park Place, New York NY 10038



The original version of this review appeared in Vol 4 #1 of Primyl Vinyl, the Audiophile Record Collectors Quarterly. For more information about Primyl Vinyl, contact Bruce Kinch, pvx@ma.ultranet.com.













































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