Some might call me a glutton for punishment, but I have taken on one of these that’s sickly and that has even had modification attempts! I’m nearly at the point of digging into the power supply. It’s great to have schematics available online, but I’m struggling with identifying ZD12. It‘s labelled as a ZD20, but I’m clueless at exactly what that specific Zener is. Would anyone know?
Update: I’m ploughing my way through the amp and thus far, have cleaned up a low level hum by simply replacing all the 40 year old electrolytics and as well, replacing some of the semiconductors in the screen regulator. Also, I replaced all the semiconductors on the 430V driver regulator board. All voltage measurements seem to be in line now and I can set all the adjustments to within the ARC instructions.
I’m still plagued with a substantial amount of noise that shows up as about 1.5 mV of HF hash on the outputs of both channels with the inputs shorted. Looking at the regulator outputs with a scope shows no major noise present.
If anyone has any thoughts or ideas, feel free to chime in.
I’m still plagued with a substantial amount of noise that shows up as about 1.5 mV of HF hash on the outputs of both channels with the inputs shorted. Looking at the regulator outputs with a scope shows no major noise present.
If anyone has any thoughts or ideas, feel free to chime in.
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New Russkie tubes, new power supply caps, fully cleaned out...
The only change is that I installed 5 way binding posts so I can use a jumper from the old style barrier strip and then use modern speaker cables terminated with bananas.
I'm the 2nd owner... bought from a friend in '89. I've had no issues with it, still sounds as new. I handle my own tube changing and biasing... easy, peachy.
But when it came time last year, in '23, to really "restore" it, I didn't touch, took it to a specialist recommended by the factory and he went over it. Didn't change much, didn't need it. I told him not to start changing capacitors unless it really needed it because I wanted to keep the original sound quality. So, almost nothing got changed, just a few here and there. (But then, it has relatively very low hours for such a vintage piece, I'd reckon no more than 2000 hours on it, total).
The unit works fine, makes music.
BTW, the amp on top is an F4. Amazing how two such different things can coexist so well. The preamp driving them is a CJ tube affair so it has nice voltage swing... Oh, yeah, neither amp will drive the Maggies past a 6, but....
The D70 was (is) so good, IMHO, because of its simplicity. Only two tubes per side. I wonder what a similarly simple amp with KT150s would sound like. They make them, but nowadays they can't help but adding bling, and co$$t, to them...
The only change is that I installed 5 way binding posts so I can use a jumper from the old style barrier strip and then use modern speaker cables terminated with bananas.
I'm the 2nd owner... bought from a friend in '89. I've had no issues with it, still sounds as new. I handle my own tube changing and biasing... easy, peachy.
But when it came time last year, in '23, to really "restore" it, I didn't touch, took it to a specialist recommended by the factory and he went over it. Didn't change much, didn't need it. I told him not to start changing capacitors unless it really needed it because I wanted to keep the original sound quality. So, almost nothing got changed, just a few here and there. (But then, it has relatively very low hours for such a vintage piece, I'd reckon no more than 2000 hours on it, total).
The unit works fine, makes music.
BTW, the amp on top is an F4. Amazing how two such different things can coexist so well. The preamp driving them is a CJ tube affair so it has nice voltage swing... Oh, yeah, neither amp will drive the Maggies past a 6, but....
The D70 was (is) so good, IMHO, because of its simplicity. Only two tubes per side. I wonder what a similarly simple amp with KT150s would sound like. They make them, but nowadays they can't help but adding bling, and co$$t, to them...
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Summer months?
See the amp on top of my D70? That's an F4. Right now I'm using it. It puts out quite a bit of heat too.
The Sissy and Aleph 2 are turned off, they really heat the room.
Our AC? Our cost is 48 cents per KwH. California Gold. 1450 KwH for the month runs around 600 bucks a month. But we're near the Coast and we have brand new, very high efficiency AC so we run it. Right now it's very hot outside, I think we hit 91F yesterday, but worse is no sea breeze and over night lows around 70F. so we've been running the ACs about 11 hours a day -off and on- to keep the house at 78F.
Currently, while I'm working, I'm listening to music in the office with a Nuforce DDA-100. My wife runs hers DDA-120.
See the amp on top of my D70? That's an F4. Right now I'm using it. It puts out quite a bit of heat too.
The Sissy and Aleph 2 are turned off, they really heat the room.
Our AC? Our cost is 48 cents per KwH. California Gold. 1450 KwH for the month runs around 600 bucks a month. But we're near the Coast and we have brand new, very high efficiency AC so we run it. Right now it's very hot outside, I think we hit 91F yesterday, but worse is no sea breeze and over night lows around 70F. so we've been running the ACs about 11 hours a day -off and on- to keep the house at 78F.
Currently, while I'm working, I'm listening to music in the office with a Nuforce DDA-100. My wife runs hers DDA-120.
Here’s a 115 for sale in Quebec, FYI: https://www.canuckaudiomart.com/details/650137809-audio-research-d-115-tube-power-amp/
Well aware of that one, thanks. That particularly well-butchered, misrepresented turd has been making the rounds for quite some time now. It actually started it's journey in a Toronto pawn shop, a couple of years ago....
The present seller initially stole photos of an absolutely pristine unit (from a Japanese website) and posted them on Canuck.
Those were taken down in short order, as using stolen images in ads is contrary to Canuck policy.
The present seller initially stole photos of an absolutely pristine unit (from a Japanese website) and posted them on Canuck.
Those were taken down in short order, as using stolen images in ads is contrary to Canuck policy.
Besides the "improvements"... where did it live? Mine was indoors, in my living room, and before that in my friend's living room ( for four years )... it looks clean. The only thing we really had to do was replace the power cord because they disintegrate over time ( become really sticky )...
I should open it up and take some pictures one of these days.
I should open it up and take some pictures one of these days.