What is Dynaco QD-2 and how/why do I use it?
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musichal
poet emeritus
I assume you use it for it's passive matrix ability to add ambience to recordings and as a crude decoder for the Pro-Logic movie experience, both for which it actually does a nice job for the cheap ticket price. Used one myself for awhile 'bout 25 years ago.
It sends a difference signal (L-R) derived passively from the amp to a pair of rear speakers and a mono signal (L+R) to the center.
Some of my friends liked the effect and when I told them they could do the same thing just by wiring their speakers up a certain way, they had me do that for them. All the Dynaco does is wire the speakers differently and adds an Lpad for the center - and adds switching so you can turn it off easily, too. Cool widget, actually. Sort of wished I'd held on to mine...but I wouldn't use it so it doesn't really matter. Fun to play with though and for music beats the heck out of all those strange-sounding cathedral, arena, etc modes.
Requires careful speaker selection for success.
It sends a difference signal (L-R) derived passively from the amp to a pair of rear speakers and a mono signal (L+R) to the center.
Some of my friends liked the effect and when I told them they could do the same thing just by wiring their speakers up a certain way, they had me do that for them. All the Dynaco does is wire the speakers differently and adds an Lpad for the center - and adds switching so you can turn it off easily, too. Cool widget, actually. Sort of wished I'd held on to mine...but I wouldn't use it so it doesn't really matter. Fun to play with though and for music beats the heck out of all those strange-sounding cathedral, arena, etc modes.
Requires careful speaker selection for success.
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hifitommy
Super Member
david hafler invented the circuit and it works VERY well thank you. mine is always on to retrieve the ambience trapped in stereo recordings. it is the circuit that dolby pro logic is derived from.
i never use the derived center channel, phantom is just fine. live recordings become more like live as the audience is allowed into the back of the room. tomita records do nicely as isao recorded with surround in mind.
i don't have a 2 which would be nice with those banana jacks back there. even the original square quadaptor works wonderfully.
i never use the derived center channel, phantom is just fine. live recordings become more like live as the audience is allowed into the back of the room. tomita records do nicely as isao recorded with surround in mind.
i don't have a 2 which would be nice with those banana jacks back there. even the original square quadaptor works wonderfully.
That can work very nicely to give you a passive surround effect. Make sure your rear speakers are as far or farther from your listening position than your main speakers, and are no more efficient than your main L/R speakers - otherwise they may draw too much attention.
musichal
poet emeritus
Yes, it does work very well for music, I agree. Also agree with not using the center channel. That was how I used mine. When I used the term 'crude' in conjunction with Pro Logic, I was merely being accurate. For Pro Logic decoding of movies, it lacks separation and misses the steering logic circuitry, and is a crude way to derive the signal, but crude doesn't mean without merit. Some folks even liked it better for movies than Pro Logic processors. However, what made/makes it really special is its use for retrieving musical ambience from those recordings in which the original venue wasn't processed to death in the mix. Tended to work best with live recordings made using a more minimal type approach, imo.
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Quadaptor is similar
One of the best systems I ever owned was a pair of Stereo 70's run in mono ( chassis grounded to each other),PAS-3x ,, QD-1 ,A-35 on the front and A-25 on the rear. Especially on Angel Melodia's - this sounded way more natural than any of the overproduced/wackily engineered "true" four channel we sold at the time. I never remember it sounding worse on anything ( 'cept maybe mono to stereo "created" stereo LP's - and they sound a bit weird on anything) and the occasional simply miked stereo recording was simply stunning.
I never saw this QD-2 box - interesting ? Anybody know about when Dynaco was selling this product.?
One of the best systems I ever owned was a pair of Stereo 70's run in mono ( chassis grounded to each other),PAS-3x ,, QD-1 ,A-35 on the front and A-25 on the rear. Especially on Angel Melodia's - this sounded way more natural than any of the overproduced/wackily engineered "true" four channel we sold at the time. I never remember it sounding worse on anything ( 'cept maybe mono to stereo "created" stereo LP's - and they sound a bit weird on anything) and the occasional simply miked stereo recording was simply stunning.
I never saw this QD-2 box - interesting ? Anybody know about when Dynaco was selling this product.?
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musichal
poet emeritus
Mid 80s IIRC, $25.
I've got one of those as well as a couple Quadapters. Haven't tried the QD-2 yet.
One of the nice things about either device is that you can use them with tubes to obtain ambience or 'surround' of sorts without introducing any solid state components into the signal path.
One of the nice things about either device is that you can use them with tubes to obtain ambience or 'surround' of sorts without introducing any solid state components into the signal path.
hifitommy
Super Member
as well i know, i use my dq1L with ALL sources and use only the derived rears coming from the dynaco box. the fronts come right off the power amp. my tubes are only in the preamp (ARC sp3a1) but their effects are enjoyed with the highly competent adcom 555II driving the speakers.
although i have a pre/pro and enough amplifier channels, i don't use 5.1, just the derived ambience from the dq1L.
although i have a pre/pro and enough amplifier channels, i don't use 5.1, just the derived ambience from the dq1L.
mhardy6647
Lunatic Member
The original Hafler product was (duh) the QD-1 
http://home.indy.net/~gregdunn/dynaco/components/QD1/index.html
This "ambience recovery" tactic led to similar products from many, many manufacturers.
http://home.indy.net/~gregdunn/dynaco/components/QD1/index.html
This "ambience recovery" tactic led to similar products from many, many manufacturers.
1tumbleweed
Kozmik Kowboy
From the looks of it, that would seem to be a much later product than the QD-1 - which came out in 1971. It has the appearance of Panor-era Dynaco, which would seem to put it post-'91...although that's awfully late for a passive quad adaptor.
That piece isn't listed on the unofficial Dynaco site - which makes me think even more that it's a Panor design. Might be a pretty rare item - although certainly with a limited market.
That piece isn't listed on the unofficial Dynaco site - which makes me think even more that it's a Panor design. Might be a pretty rare item - although certainly with a limited market.
musichal
poet emeritus
Does anyone know if the Lepai 2020+ amp can safely be connected to derive the L-R signal? This sort of combines two current threads, but I have wondered previously whether the cheap little Lepai could be used this way, so this seems a good time and thread to inquire.
The connection for deriving L-R is connect from pos of L amp output to pos of L speaker, connecting pos R amp output to pos R speaker, then connecting the negative of the two speakers together. No connection is made to the negative outputs of the amp. This is what the QD-2 does internally to derive the ambience (L - R) rear signal. Some amps (I think some that do not share a common ground at outputs) cannot be connected this way without damage, how about the t-amps? Could be a fun use for them, if okay.
The connection for deriving L-R is connect from pos of L amp output to pos of L speaker, connecting pos R amp output to pos R speaker, then connecting the negative of the two speakers together. No connection is made to the negative outputs of the amp. This is what the QD-2 does internally to derive the ambience (L - R) rear signal. Some amps (I think some that do not share a common ground at outputs) cannot be connected this way without damage, how about the t-amps? Could be a fun use for them, if okay.
hifitommy
Super Member
the black boxes are definitely Panor Corp who also offered a range of tubed products including a reissued st70.
i got my first qd1 in about 1973 and fell in love with the sound improvement it yielded. i still use a QD1-L all the time and wouldnt want to be without it. not one of my audiophile/music lover friends that have heard my system noticed it until i pointed it out and none objected to the sound.
to address musichal's question-an amplifier must be able to function in common ground. i believe that eliminates monoblocks or amplifiers of dual mono configuration.
i got my first qd1 in about 1973 and fell in love with the sound improvement it yielded. i still use a QD1-L all the time and wouldnt want to be without it. not one of my audiophile/music lover friends that have heard my system noticed it until i pointed it out and none objected to the sound.
to address musichal's question-an amplifier must be able to function in common ground. i believe that eliminates monoblocks or amplifiers of dual mono configuration.
WaynerN
Addicted Member
I think to get the center channel to balance out, all 3 speakers (L, C and R) must be exactly the same speaker, or it doesn't work well. In fact, all 4 speakers should be identical.
Wayner
musichal
poet emeritus
I seem to recall that some cheap lo-fi amps in all-in-one type receiver/tape/TT combo units couldn't be used this way, but I could be mistaken. Some cheap configuration in which the outputs did not share a common ground between L & R channels. I had been thinking of using a Lepai this way but was not certain if it's appropriate.
hifitommy
Super Member
a place to put this question would be:
Amp/Preamp Asylum http://www.audioasylum.com/forums/amp/bbs.html
there are usually some pretty informed posters there.
Amp/Preamp Asylum http://www.audioasylum.com/forums/amp/bbs.html
there are usually some pretty informed posters there.
Welll You can certainly try.. But IMO/experiences the Cheap Lepai is Unmitigated JUNK. I've had 2! fail identically while in use.
One speaker channel simply stops working, for No discernable reason.
And No, both were entirely different configurations using everything different.
Clearly not the same dumb mistake repeated.
Be aware that Tripath ceased on mid 2000's as did their chip production.
What is on the market are cheap/crappy Chinese clone/fake chips. Some say made in Korea others say USA.
Some even have gold pins. All are junk.
These are of Low quality and prone to early/unexpected failures.
Also from experiences the original Dyna Quad speaker circuit config.. works.. Sort of
The Later Panor version is more complex and by no stretch a Classic or forward step... Like everything Dyna that Panor bungled... just not quite good enough.
Shame actually.
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