Quatre QMI Gain Cell Series Amps - diyAudio
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Old 25th August 2010, 05:41 AM   #1
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Default Quatre QMI Gain Cell Series Amps

Hello, not sure if this is the best place to seek answers but this forum popped up as an option when searching the net for info about Quatre Gain Cell Series Amplifiers. Want to know how to approach powering them up for the first time in probably 6-10 years. One is a DG250C and the other a GC500 the internals in both look fairly clean although showing signs of possible repairs or up-grades... etc, and both look like fairly substantial pieces of gear with one (GC500) having the most enormous power transformer I’ve ever seen on any piece of music gear to date period. A friend of mine got them out of a storage room in a club where they were once used as the house dance pa system and I don’t even know if they work or not. Given the nature of the situation it would seem reckless to simply load the speaker out’s and just plug it into the wall due to the size of the capacitors and the adjacent delicate looking pc boards with small chips standing off the board.

I’m hoping that I could use these (or one of them) for an alternative s-state system in my home as I do enjoy the clarity and POWER of a good s-state amp as an alternative to several tube amp sound systems that I currently own and rotate periodically. I had to sell my last good s-state power amp about a year ago due to relocation cost and I miss it. It was a JBL/Urei 6260 power amp and I used it mostly to power my Altec Valencia’s that also had to go about a year prior. Anyway… enough sob story telling. Any advice on these amps? Things I should know? Like, how to control the levels as there aren’t any on the amps themselves?? And the safest way to test power them up would be greatly appreciated. Again i have 2 amplifiers… Quatre Gain Cell Series DG250C QMI and GC500 QMI.

Also: I'm a diy-er that probably should have been on this forum a long time ago and looking forward to sharing ideas and learning more about how to tweak, mod and make usable circuits.

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Old 27th August 2010, 05:21 AM   #2
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wellp... i've read most of the previous threads about the Quatre qmi amps since my first post and have the most important question answered being these are basically "lemons" which means (to me anyway) not much threat in powering them up to see if they're working. Havenít yet decided what to do if they seem to function ok.. maybe use them or sell them, i like the idea (read from some of the post regarding these amps)of recycling them for parts if they don't work. Also enjoyed reading the link to the electronic attenuator patents posted on one of the threads. personally why bother? Seems much more simple and reliable to have the control at your finger tips. i see that some did read my post so thanks for that anyway and a belated thanks for the info already provided in past discussions.
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Old 7th September 2010, 08:03 PM   #3
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the DG250C works great! although it's high-mids seem a little too strong for my taste had to back the "presence" way off on the decade 36's, but i still can't tell if it's just my own not being use to a good powerful amp or if the amp is distorting around those frequencies??

GC500 has a problem with the right channel...barely audible and distorted. going to replace 9 amp fuses for the right chan and see if it holds out. if the fuses blow again i'll bring to one of the techs at my work... if that proves failure than i'll sell parts. gonna have the dg250c checked out as well just for assurance
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Old 7th September 2010, 09:15 PM   #4
SY is offline SY  United States
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I don't know if it used electrolytic coupling caps on the input or electrolytic caps in the feedback loop to null offset, but if it does, those would be the first components I'd replace; age is not kind to them.

Man, I haven't seen or heard a Quatre in decades.
"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."
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Old 8th September 2010, 03:41 AM   #5
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are you refering to my comments about the dg250c being kinda Brash sounding? or the other gc500 with a bad channel?? I'll check the caps on the gc500 tonight and report. Thanks!
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Old 20th September 2010, 08:18 PM   #6
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going to sell these amps. after considering what I've read about their general temperament being doubtful, i don't wanna hassle with them. going to sell them together for 100 bucks. not trying to spam out the forum here but Ive read the it's possible to cannibalize the chassis and power supplies for a complete reworking of another amplifier design ... a project way beyond my diy abilities. i'll post them on ebay as well as the marketplace on this forum and donate a percentage to the forum if the buyer is from here.
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Old 20th September 2010, 08:52 PM   #7
PH104 is offline PH104  United States
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Originally Posted by SY View Post
I don't know if it used electrolytic coupling caps on the input or electrolytic caps in the feedback loop to null offset, but if it does, those would be the first components I'd replace; age is not kind to them.

Man, I haven't seen or heard a Quatre in decades.
Both places in the DG250C for sure and I would guess in the GC500 as well. Tantalums to boot.
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Old 9th October 2010, 09:11 PM   #8
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sold these amps to a forum user! I did check the caps before i sold them in the GC500 and they messured close to spec...(86k uF i think) not spot on but i didn't disconnect the leads to them either. the main power supply caps are wired in series, 2 sets of 2.
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Old 1st January 2012, 06:22 PM   #9
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I recently replaced my apt preamp and quatre dg250 with a denon home theater system. they are both in excellent audio and physical condition. One owner only. Downsizing due to age (mine) and the wife's refurnishing desires. Anyone interested?

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Old 16th January 2013, 04:04 AM   #10
xtechee is offline xtechee  United States
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Smile I had 2 of these Quatre gain cells years ago(1981)

The dealers had to refund the customers money because they could not keep them working. The dealer in Seattle Wa. had a stack of them. They oscillated and blew up. I removed the original circuitry, and replaced it with my first designs. I still have some of the driver boards, and have drawn the schematics. They were ahead of their time. The original engineer just didn't do enough testing. He did not follow through and finish the design. Anybody know the name of the engineer who designed them?
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