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robertbartsch
10-23-2008, 02:06 PM
Is any one using this 200 WPC amp?

I just scored one on Flee-Bay a few days ago for cheap ($275 USD). I assume this amp is >20 years old. Typically, I don't mess with old electronics but I thought I would be adventurous.

Do amps deteriorate with age or do they generally stay within the orignial factory specs?

pentictonklaus
10-25-2008, 05:34 PM
Since nobody else answered this, I give it a try.

I listened once to this Adcom and it did not seem to be all that bad.

To answer to your question, yes components do age. I did read a statement by Nelson Pass saying that you have to expect capacitors failing or going out of wack after some 20 years or so, totally depending on the hours that have been put onto the machine. That is also the reason why some folks modify the crossovers with new caps and claim a new found found heaven.
Transistors fail as well, sometimes early or late. Every amp needs DC fault protection ( if not built in ) or will send drivers many times the value of the " E-Bay lucky find " " to speaker heaven.

If you like the sound of the Adcom enjoy.
Please check with the manufacture or any specs you can find what kind of protecton curciuits are standard with this model.

If it is not a part of this amp, go and buy some external DC protection from Parts express as often dicussed in this forum. I learned this the hard way some years go when a Crown DC 300 a went DC and sent a couble of 2231 to recone hospital.

Klaus

robertbartsch
10-26-2008, 03:08 AM
Thanks....

I'll check the DC protection circuts on the "old" Adcom. I did note that the unit has 5 fuses at the back of the unit between the heat sinks. Is that a sign of DC protection or something else?

Uncle Paul
10-26-2008, 10:34 AM
Here is the manual:
http://www.adcom.com/data/manuals/gfa555IImanual.pdf

robertbartsch
12-03-2008, 12:06 PM
Ok, so I have had a chance to listen to this older unit for several days now using a pair of 4312 monitors.

The unit has good power for its 200 WPC rating.

I believe the mid range is relatively flat sounding. The bass and treble are a tad over bearing in my opinion, however.

I have owned many higher power amps in my day (Denon, Marantz, Onkyo, etc.) but I find the newer Crown XLS amps are very nuetral and flat sounding from the bass through the treble range.

All-in-all, I would recommend avoiding older amps in favor of the newer designs which I suppose are better in every way.

BMWCCA
12-03-2008, 12:25 PM
All-in-all, I would recommend avoiding older amps in favor of the newer designs which I suppose are better in every way.And maybe your conclusions are subjective and influenced by what you're used to listening to? :)

robertbartsch
12-03-2008, 12:55 PM
I suppose most listening tests are subjective and judgemental. I have 4 systems in the house now and I have had the JBL 4312s monitors on three of them so I think the too big bass and too big treble on the Adcam is real.

Anyway, I got the amp at a good price, so I will run it in the basement system for now.

LE15-Thumper
01-02-2009, 12:27 PM
I used to do warranty on Adcom products and I must say all in all they represented some of the "bang for the buck" products out there. A few models had some quirks, but their power amps were quite solid.

The "triple nickel" as we called it was probably the best amp they made until the newer stuff came out in the new millenium.

I remember bench testing (on my Sencore PA81) the "little brother" GFA-545II and getting close to 180watts per channel (both driven into 8 ohms) at onset of clipping. Not bad for amp under $700.00 rated at 100wpc.

I should say that in more than 10 yrs of doing service on this brand, I only saw ONE failure (On the 555) that required changing of the ouput devices. Most failures were 10 and 100 ohm 1/4 watt fuse resistors that would open causing grounding issues on the front end thus causing DC offset putting the amp into protection mode.

The output stages were insanely robust for what these units sold for. And as mentioned in this post, they had a very nice sound to them as well.

rj2077
01-02-2009, 02:34 PM
what pre amp are you using? i have a pair that i run in mono. i either use a threshold , coda 02b (fet) or a old scott tube pre and get great results. they sound best with the coda. try it, you might find that they are not that bad. at 200 wpc for $275, they are a bargain.

regards

robertbartsch
01-04-2009, 12:01 PM
I'm using the Adcom 5 channel preamp.

Unfortunatly the amp seems to be malfunctioning now. The speakers have clicking noises when driven moderately hard.

Does the Adcom 555 II have DC protection?

robertbartsch
01-05-2009, 05:26 AM
I don't believe the Adcom 555 II has DC circuit protection from what I have seen on the Net.

jblnut
01-06-2009, 09:37 AM
A friend of mine had this amp in his system back in the mid 80's. It was paired with some Snell speakers, an Adcom Preamp and a Sony ES CD Player. Your comments about flat midrange and boosted highs and lows match my memory of this perfectly. The highs would give a set of 901's a run for the money as "paint peelers". Whether this was a trait of the Snells or the Adcom (or both) it's hard for me to say now.

I will say that I have really begun to realize that *everything* in a system can and will influence the sound. The speakers (and the room) are the biggest part of the equation obviously. But amps and even preamps can really change the sound dramatically if your speakers are transparent enough to reveal it.

jblnut

robertbartsch
01-06-2009, 12:21 PM
Yeh, I suppose it will be a hard decision on whether to repair the Adcom power amp.

I bought it for $225 but I don't really want to put more than $100 into an old unit like this.

robertbartsch
01-06-2009, 12:31 PM
Yeh, I suppose it will be a hard decision on whether to repair the Adcom power amp.

I bought it for $225 but I don't really want to put more than $100 into an old unit like this.

adac1966
01-18-2009, 03:50 PM
I have an Adcom 555 II that my sister-in-law bought new along with preamp/tumer and CD changer. She has not used them in over 10 years since she moved. She asked me to sell them for her but when I hooked up the Amp, one channel is not working and the light is on. Is this a capacitor problem? Should I just sell it as is? It's in great cosmetic shape and used to work fine before she put it away.

hjames
01-18-2009, 04:09 PM
I have an Adcom 555 II that my sister-in-law bought new along with preamp/tumer and CD changer. She has not used them in over 10 years since she moved. She asked me to sell them for her but when I hooked up the Amp, one channel is not working and the light is on. Is this a capacitor problem? Should I just sell it as is? It's in great cosmetic shape and used to work fine before she put it away.

Could be most anything ... best to have a shop look at it and give you an estimate.

jbl_daddy
01-19-2009, 07:03 PM
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...

robertbartsch
01-20-2009, 10:29 AM
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.

adac1966
01-20-2009, 07:55 PM
Thanks for all the responses. Easier to sell as is for repair or parts.

RedZCar
03-13-2010, 10:59 PM
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.

scott fitlin
03-14-2010, 05:35 AM
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! :)

svollmer
03-14-2010, 06:26 AM
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...

I have a totally different experience. I own five of the Adcom GFA-565 monoblocks (there was never a series II of the monoblocks) and I love them. I used to use four to bi-amp my Legacy Focus before I replaced them with a 175lb Mark Levinson 332 that I got for a steal from a friend. Yes, the Levinson is better than the Adcoms, but it doesn't blow them out of the water. The Adcoms also have much more ass in the low end. I'm really confused with your experience of them being "dirty/muffled." If anything, Adcoms are criticized for being a touch too bright in the high frequencies.

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.

hjames
03-14-2010, 07:56 PM
And I love the pair of GFA-555 (early model, not the IIs) that I replaced my JBL/UREI amps with ...





http://audioheritage.org/vbulletin/attachment.php?attachmentid=43645&stc=1&d=1263065976



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.

SEAWOLF97
03-15-2010, 07:52 AM
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.

RedZCar
03-15-2010, 11:39 PM
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?

RedZCar
03-15-2010, 11:52 PM
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
the followers.

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 22F 100V to each of the four 15,000F 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...

SEAWOLF97
03-16-2010, 04:54 PM
According to a quote from diyAudio attributed to Nelson Pass:

thanx for that post RZC....in all that I've read, nobody really claims that one version sounds better than the other ......if you have a bargain in one hand and money in the other, I wouldn't let the series number stop you...:D

1audiohack
03-16-2010, 10:51 PM
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!!!

svollmer
03-17-2010, 05:22 AM
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!!!

I don't know if any will catch fire, but maybe the "Satan" amp (S/N 0666) might spit fire!!! :duck:

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.

SEAWOLF97
03-18-2010, 10:27 AM
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.

SEAWOLF97
03-21-2010, 11:27 AM
I did notice that the GFA-555 does not show COO ...assume USA , where the II clearly shows "made in Japan" ..doesnt bother me, but I wonder if this plays into the story somehow ??

robertbartsch
03-23-2010, 01:42 PM
I got mine back from the repair shop a few months ago but I have not tested it yet.

I think it was a bad output stage....

Anyway, this kinda sours me on old electronics.