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Adcom GFA-585

Stereo Power Amplifier

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Adcom GFA-585


Power output: 250 watts per channel into 8Ω (stereo)

Frequency response: 10Hz to 20kHz

Total harmonic distortion: 0.02%

Damping factor: 600

Gain: 27 dB

Input sensitivity: 2V

Signal to noise ratio: 110dB

Semiconductors: 72 x transistors, 11 x zener diodes, 31 x diodes, 2 x IC, 2 x diode bridges

Dimensions: 213 x 432 x 310mm

Weight: 20.5kg


service manual   English -

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Reviewed Feb 16th, 2016 by kmh3212

When I bought the amp off *bay it had a loud pop on startup and shutdown. I knew this going to do damage to my speakers. I raised the hood and suspected bad caps. That was a year ago. I cleaned up several projects and plugged it in and turned it on. The problem went from bad to a lot worse. Went ahead and ordered the caps on the input boards. Since I waited the electrolyte corrosion may have compromised a tracing or two on the boards. Now I have to repair that too. We will see. I must say after the startup pops was working fine but definitely not perfect as the seller sold it to me.

Reviewed Jul 31st, 2015 by mobay

This is a monster of an amplifier bar none. 250watts ( more like 270 + ) and a damping factor of 600...ouch! This amp will drive ANY speaker on the planet. It has one fatal flaw however.All of the capacitors should/must be replaced. This was not Adcom's fault but in the year this amp ( and for that matter many other electronic devices ) was made a group of faulty capacitors were sold, but hey ,they were less expensive, than the Japanese equivalent.. All of these would leak and fail and can result in the destruction of a speaker connect to this amp. A large THUMP on startup or shutdown tells you that you are on borrowed time. I paid $300.00 for this amp and although mine was not leaking , I replaced all the capacitors. There is a firm in NY that can do this and they charge $425 for the repair. YOU can do the repair if you are careful. Go to audikarma.org and do a search for this amp and you'll see the thread on it's repair.

OK now with that said....... did I mention that this is a monster of an amp? The torroidal transformer is rated at 100,000 uF and the unit weighs a ton ( not really but it's super heavy ) . Sound quality is great and I would characterize it as dark/neutral. The sound is effortless, and so clean that you may damage speakers with the high output because of the lack of distortion at high levels. Use fuses ( 3 amp fast blow ) to protect your speakers from excessive output that this amp can easily produce. It is that powerful.., and Oh! so very clean and undistorted=== Once fixed this amp is probably worth close to $800.00 or more and the actual cost of the replacement capacitors needed is less than $50.00. A great return on a small investment. A truly exceptional amp whose reputation was marred by a unfortunate choice of parts from a supplier who sent Adcom, and many, many other manufacturers sub-standard parts. Ask whoever is selling this amp if the capacitors were replaced and the circuit boards cleaned. ASK THEM TO SHOW YOU A BILL certifying that the work was done. If they cannot, Do Not pay more than $300.00 ( or less ).



re: GFA-585

Well I found a GFA585 on eBay and delayed hooking it up. I finally got around to it and the first thing I noticed was the hazardous thump on startup. I was thinking uh oh that's not right. I have 4 Adcom amps now and never had an issue. I got on HIFI engine and looked up the schematics and had a place to start looking when I found the delay on startup circuit. I suspected a stuck closed delay relay. After reading the comments section I found I have some work to do. BAD CAPS!
I have never had any major issues with Adcom amps in the past. Small easily fixable stuff on one amp. Mobay comments above tell me of the bad cap problem. I went through this on computer mother boards several years ago. Manufacturers saving less than a dollar on caps caused the ruination of millions of computer motherboards. At least these amps appear easy to work on.

re: GFA-585


There is an extensive thread or threads on the cap replacement. Make sure you do photos extensively so you can trace the steps you've taken. In retrospect the replacement and cleaning of the capacitors and boards was not THAT bad, just tedious. It was certainly not expensive either. It is expensive if you have it done for you at a shop. These really are superb amps once they are fixed, and will probably outlive all of their owners once running. They are super powerful ( mine measured 282 watts ) and provide effortless power .

Good luck with yours


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