I had a pair of Adcom mono block 565 Serise II's in the early 90's and they sucked, they just sounded dirty/muffled. Sold them and purchsed a pair of Crown PSA-2's, night and day difference. If it was me I would not sink any money into it. eBay it for parts. :barf:
Before you sell it, hook it up to a different preamp and use different cables. You never know...
In perfect shape it is worth about $275.
I would take it to a repair shop and ask them to provide you with an estimate to repair.
Thanks for all the responses. Easier to sell as is for repair or parts.
Couldn't disagree more. The Adcom 555II received industry-wide praise when it was introduced as an upgrade to the GFA-555. This is an audiophile quality amp, not a sound reinforcement amp as are Crowns. It is so popular, in fact, that Adcom has re-introduced it as the GFA-555SE and I believe it is on a special order basis.
A GFA-555II with no known problems, good cosmetics, and original packaging will commonly garner $425 on ebay. If you bought one for $275 (or was it $225?) the seller probably had known issues, bad cosmetics, or you were just lucky.
I have several friends with 555s or 555IIs coupled to 4311s, 250Tis, and other JBL speakers and they all sound damn good to me. I do think my marantz sounds just a smidgen better through my LSR32s or my Focal-powered Aria 7s, but I do use a 555II to drive my two JBL SUB1500 subwoofers and they're are still loosening the sheetrock since 2004 and never get warm. (I know some of you who have built subwoofers around the SUB1500s think they need more power, but honestly, in my 3400 cuft listening room my subs deliver so much acoustic power it is unnerving - and all I'm using is the 555II.)
For the guy with one channel out, if it is a 555II (as opposed to a 555), check the fuses on the back panel - the four fuses in a row are power supply rails and the condition you describe could easily be caused by one of these four fuses having failed. Check the two fuses on the side (channel) where the led is "on". Of course, turn the amp off and wait 5 few minutes before removing any fuses. If one of these fuses has failed, contact Adcom for a replacement as they are special fuses you are unlikely to find at Radio Shack or automotive parts store. The fuse adjacent to the power cord is the AC fuse so it doesn't need to be checked if the amp is powering up. If you don't know how to check these fuses, take the unit to any reputable electronics repair shop and have them put a meter on each fuse. You might get lucky a second time and find that the repair is simple and cheap. If it is a 555, you'll have to remove the cover to get to the power supply rail fuses.
Unfortunately, industry praise, and what people like do not always go hand in hand. Yes, the Adcom amps received alot of praise, I listened to them several times. To me they were ok, but I didn't run out and buy them.
Back in the 80,s, in my neighborhood we had a restaurant/bar called Justins, and I frequented the place alot. It was our upscale neighborhood watering hole and eating place, and everyone from the neighborhood came to socialize there. They had the Adcom amp, Adcom preamp, a CD player, and Rogers speakers. When Justins renovated they made a big deal about the system they put in. I knew the owner well, and he knew my families place too, and one day he called me and asked IF I had an amp he could use for a week while the Adcom was being repaired. So I brought a DC-300A to the place, put it in, and we all were very surprised at the difference in sound.
All Tony kept saying was BUT I paid THIS much for the Adcom amp! You get the picture, I'm sure! :)
I guess I'll sell them at some point just to clean house, but for now, I can't let them go. They do have a problem with input capacitors leaking, but I've had all of mine replaced recently by an ex-designer for Conrad Johnson who started a repair shop in Northern Virginia. So if you're thinking of buying any used, make sure the caps have been replaced or get them replaced. And, as I've told Heather, the tech warned me sternly to NOT get a used GFA-585 (two monoblocks in one box) because it's almost impossible to fix them when the capacitors leak.
I also own a GFA-555II and have never had a problem with it. I used to use it bridged to run my two 2245H subs. My dad has a GFA-555 and it's been flawless. FWIW, until recently I also had a 545 a 535, and a 535II; all performed great with no problems.
And I love the pair of GFA-555 (early model, not the IIs) that I replaced my JBL/UREI amps with ...
I have the first GFA-555....did some reading on it ...thats the model with the Nelson Pass association...what i read was that Adcom cheapened it and simplified NP's design on the II .
Mine was DOA , thus "free to a good home" ....external fuse was OK, but 2 internal ones were blown...replaced these and doing well ever since.
Had it running the 250ti's for a while....found no problems..very dynamic and solid....a likeable sound...currently pushing the Walsh F's that are rated 4/3 Ohm....doing just great....wud not hesitate to recommend.
It is my understanding that there were NO circuit changes to the 555II, rather they placed the power supply rail fuses on the back panel so they could be user-replaced. It is also my understanding that other mark II models (545 & 535) did have some circuit changes. As far as component changes between the original and 555II, I'm not sure, but I'll be pulling two original 555s from a rack next weekend and I'll pop the top and take a look at the output transistors, power transformer, filter caps and other expensive components and compare to those in my mark II.
I vaguely remember the Crown DC300A. Wasn't it introduced in the early 70s and used about a zillion dBs of negative feedback?
According to a quote from diyAudio attributed to Nelson Pass:
"I designed the 555. I believe the Mk II added a couple
of what were considered improvements, and it seemed
to me that it included triple darlington outputs instead
of 2 follower. I might have the schematic around, but
all told it was a simple bipolar design with a current
sourced input diff pair followed by a common-emitter
gain device that was also current sourced. This drove
It was typical of all the 5XXX amps that I did the first one
and then they improved it until it had too many parts,
and then I would design the next in the series http://www.diyaudio.com/forums/images/smilies/smile.gif
Americo Borza sent me an old 555 in the hopes that I
would update it, and it still sits here, a perfect candidate
since so many of them were built.
Personally, I would score a few of these and run them till
they die and then update them. If you wait long enough,
an update will be issued. "
Another diyAudio contributor (an authorized Adcom repair tech) wrote:
"The original GFA555 as built by Adcom had a couple of small problems. The 2SA1011/2SC2344 driver transistors blew when the fuses went, driving low impedance speakers (Infinity). The Adcom fix was the 2SB633/2SD613 pair, selected for high voltage. These were a real problem as the un-selected part was only 100V. and every now and then the 'selected' part would puke. I used the Motorola MJE15030/31, a 150V part, without any problems. The power switch had a short life expectancy. I added a CL-30 Keystone inrush current limiter and a Hafler DH500 relay board with a three pole relay, the third pole shorted out the CL-30. The bass sounds much tighter if you add a 22µF 100V to each of the four 15,000µF main filter caps. The MKII version was strictly a cosmetic upgrade. (Italics mine) The GFA585 had the triple output stage with cross coupled dual differential inputs and power supply bypass caps, and a DC servo. My modified 555s had much more 'slam' than the typical PA power amps of the era, and cost cost me considerably less. I used modified DH500s for mids and highs."
And so it goes...
I have nothing but good to say about my Adcom amps. I bought new in (1991?) two GFA 585's and one GFA 565 and have used them almost daily ever since with absolutely zero issues and quite like the sound of them. The 585's were limited edition, (probably limited to however many they could sell) one of mine is serial #0666. They are beautifully built inside and out. I am in fact listening to one right now. I've heard over and over about how problem prone they are, mine have been great. Of course having said that one of mine will catch fire tonight!!!
Seriously, you may consider having the input caps replaced on the 585's even though they're not leaking. The tech told me that it's a real bear (and much more expensive) to clean the board once it's soake with oil. Again, I've only heard of this leaking cap problem on the 565 monos and the 585. I haven't heard of it on any of the other 5 series.
I wish someone would make "plug and play" replacement boards for them. Might be a nice small side business for the right person.
AdCom GFA-535 Amp High End Audio - $150 (SE Portland)
Date: 2010-03-17, 6:31PM PDT
Super high end audio equipment. I have other stuff so this is just sitting around.
I paid a lot for this and it is worth more than what I'm selling it for.