Adcom GFA 585 Part 1 - First Look

[@williamcampbell3868]

I have a Adcom 555 mk2 which has worked flawlessly for almost 34 years. The limited edition was a stereo amplifier rated at 250 watts per channel. Higher than the 555 but lower than the monoblock 565 which was 300 wpc.

[@f430ferrari5]

I have the Adcom GFA-5500 which is the next generation. I’ve have had for over 20 years. Works perfectly and sound great.

[@brianmacnamara8774]

You never cease to amaze in what variety of things you come up with. Always useful info and totally entertaining. Thank you as alway, Tony!

[@billmilosz]

I've had a 555 MK II for 30 years without any trouble. Bought it used. I opened it up for the first time last fall, I adjusted the bias. No bulging capacitors or other issues to be seen. Works flawlessly. I use it in a tri-amp setup, up to 200 Hz.

[@xraytonyb]

The capacitor issue was in the first generation gfa series. The MKII series used different capacitors and didn't have the problem.

[@billmilosz]

@@xraytonyb I see

[@dell177]

i worked for a power supply company who went through that capacitor armagedon. We made hundreds of high voltage supplies that used a number of 10uf 450v caps that proved especially subject to this problem, the lower voltage electrolytics did not suff from this. We found there was a change across the industry in the sealing process that made the seals in these commercial caps sensitive to flourocarbon based cleaners. Military caps have much better seals and were not subject to this kind of failure. If you cleaned the boards with that kind of cleaner (Trico or Freon) it attacked the caps and they would leak and fail in a matter of months. This problem led to the creation of water cleanable fluxes to get away from the old rosin core fluxes.

[@GumballsAmazingWorld]

Ran across this. Don't see Adcom talked about very much anymore. I recently pulled out all of my old Adcom equipment that's been put up since the early 2000's, bought back in the early 90's. Still impressed. GFA 5500 GTP-450

[@g.fortin3228]

Watching some of the older ones.. going to enjoy this series !

[@peekaboo4390]

Wow ... very interesting. I was going to look out for some Adcom.

[@garybevis8691]

I owned a GFA-555 many years ago, it had amazing damping factor and drove a 6 ohm load like a champ (Boston Acoustics and JBL's) it worked great for about 4 years and one morning it destroyed itself with a loud bang. It was dead and at the time I was not working with electronics. $1000 down the drain. I could never find anyone that would repair it. That was 1999 when it let go, I bought it new in Oct. 1995. I had suspected that was the reason recently, at the time I did not know about the failures of electrolytic capacitors, as Tony said, polite people do not talk about capacitors...lol

[@phloodpants]

The GFA-555 didn't suffer from the epidemic capacitor issue as the 565/585 did. It's a completely different design. I very rarely see bad capacitors in GFA-555s, but it does happen! I'm surprised you couldn't find anyone to fix it. It's a super straightforward design, and all the parts are still available. I suppose the boards could have been burned beyond recognition?

[@misterhat5823]

Awesome that you're restoring it. I'd call this a parts amp.

[@goodun6081]

I have fixed a number of similar-model Adcoms that had been damaged by the capacitors leaking. ( the audio input boards are where the real problems lie). Cleaning the boards and replacing the adjacent corroded components can be time-consuming, but it's do-able. Fixing the electrically conductive leakage where the fluid has soaked into the board involves cutting some foil traces and component connections and remaking those connections with flying leads perched off of the board somewhat. It's perhaps not that elegant-looking, but it works fine. By the way, the fluid that leaks out of the capacitors is brown and tarry looking, looks like something that would come out of a spittoon, and anything you solder or unsolder that has been contaminated by this group will give off a fishy smell when it is heated. Frankly, if you have an Adcom amp and the Caps haven't appeared to started leaking yet, they almost certainly will and I strongly recommend that you replace them prophylactically in advance.

[@phloodpants]

Yes, especially if you have a GFA-565 or GFA-585 with the original Elna caps. There is a 100% chance they are leaking. Many GFA-555/545/535 model's capacitors are still working OK, but they are getting old so might as well replace them with newer, better ones.

[@goodun6081]

@@phloodpants , "Able was I ere I saw *Elna* !" Real crap caps those are, and they're everywhere. "Shoei" is another common capacitor brand found in vintage audio gear that should always be replaced.

[@brucelewis9848]

Bought a 565 system new in I think 1994-5. Modded with black gate caps high performance rectifiers etc. still sound great

[@dell177]

Back in the day our company was building a lot of HV power supplies (1 to 4kv at 10MA) for medical uses. We used to use a shitload of 10UF 450v caps in series on these amps and all of a sudden the caps started to fail in droves. Back then we used to use trichlorethalene to clean the flux off PWB's after going through the wave solder process, it did a beautiful job of cleaning the boards. At one point the industry started to use a new sealing plug in the vent of electrolytic caps and these new vent plugs could not stand trico. A couple of months down the road the caps would fail. Any cap that had been cleaned the old way was GOING TO FAIL. The solution was to use alcohol to clean the boards not trico. Alcohol does not nearly as good a job cleaning the boards but it also does not damage the caps.

[@neilwhiteaker53]

Outstanding presentation, Tony! Thanks so much.

[@petecap4382]

I just wondered onto your channel Thxs a bunch I have a 585 I will investigate.

[@mikeday62]

I'm waiting for my newly purchased Adcom GFA 535 II, to arrive this week. I live in a small town, not sure how many technicians around here. Hope she work really good like seller told me. 😹

[@briarboy8959]

My GFA 555 II that I bought new in the early 90’s still going strong, may take a peek inside now.

[@xraytonyb]

The original GFA 555 was the one with most problems. The 555 II used better capacitors and weren't as prone to this happening.

[@RanTausi]

@@xraytonyb I own GFA 555 MK2 and the 545 MK2 and GFP 565 Preamp , they are remarkable.

[@williamcampbell3868]

To@briarboy8959: You will only have to gently wipe away some dust that accumulated over time through the ventilation holes in the top of the amplifier. I performe this every other year. Make sure the amplifier is unplugged and not used for several hours or the next day before your next listening session. Use a slightly damp cloth and carefully wipe all dust and use q-tips for tight areas. Let dry for a while(not that it's wet) screw top plate back on and listen for many more years my man!!!

[@thedogefather]

I hope you also find a GFA 555 to do very interesting stuff. I have a 555 so quite interesting to me and my Magnepans

[@TemperTemper...]

I have an Adcom GFA 535 60 watt per channel amp that I bought new over 20 years ago and it is still working fine.. Hopefully this one didn't have the bad type of cap...

[@cbayardelle]

My gfa 555-2, after using the amp with magnepan speakers started making a pop in the speakers after turning the amp off, a year ago it was a minor pop now it is very loud, I stopped using the amp. I purchased it new in the 80’s.

[@FrankenShop]

I really appreciate the insight into these amps. I have three GFA-555 that run my home theater system and so far as I'm aware, they have never been recapped and all 3 are operating fine. I'll plan on pulling them out of the rack and doing a careful inspection. I may go ahead and replace caps even if they look ok. Thank you again!

[@johnkleppan8454]

OMG you have 3? Back in the day I lusted after Adcom, S.A.E. , Soundcraftsmen etc. but was never able to swing the purchase. Always hought they were close to "pro PA" level sound for the home. Bravo!

[@FrankenShop]

@@johnkleppan8454 Indeed, I bought them back in the late 90s and they've been the backbone of my various home "theater" incarnations over the years. I was fortunate to work part-time for a while at a high-end audio/video shop that dealt heavily in used equipment and I traded time for credit toward equipment, otherwise I would never have been able to justify the cost. There was also no internet back then so without those types of specialty shops, there was no easy way to buy/sell like we have nowadays.

[@phloodpants]

The GFA-555 never had any epidemic capacitor issues. I see very few leaky caps on 555's; just random failures here and there, as one would expect. The GFA-565 and GFA-585 suffered from a bad batch of caps from Elna, a good manufacturer. But yes, it's good to replace them anyway.

[@ThejasonJaw5442]

Your video's Teach Me so much

[@johnedel5953]

Did this also happen with the 6000 model?

[@ericschulze5641]

What fails that causes the speakers to fry ? I'm considering getting a working adcom 6000 & hitting it with the parts bomb, the guy did say it blew a fuse but replaced it and it works now , im not a good diagnostician but am definitely capable of doing a quality rebuild I've recapped several working recievers. and having my amp technician friend test it out when I'm done, I don't want to pester him with 10 million questions he's retired and kinda grumpy

[@carlubambi5541]

I had 3 of the 555mk2 I am down to one .No capacitor leaks but the other 2 failed within 2 years from when i purchased them .I have one left and it's still working flawlessly .it's time now for a recapping but what a difference 30% failure rate on adcom .I have my old Sony STR v6 which runs every day .Not one component failure exception One lamp so I re lamped the whole thing .How could they screw up so bad .

[@freightdawg6762]

What about the v2 of the gfa555 any better?

[@3rdaxis649]

Fried a pair of Dev Tech BP-20's because of these amps.

[@TheMaxx111]

Did the GFA-555ii have the same capacitor problems?

[@RanTausi]

No.

[@Mr_Meowingtons]

The good old capacitor plague of the early 2000s

[@jimbosammy4255]

And where might the GFA7700 fall ? Getting ready to sell mine cause we are moving to a Condo. Drives my Polk SDA 1.2TL's with ease.

[@larryguise995]

there was also a gfa-545. i believe it's around 100 wpc

[@ronshaw80]

And a GFA-535, 60Wpc.

[@phloodpants]

Yes, all excellent amps. The GFA-535, 545 and 555 all share the same basic circuit. The 535/545 use identical boards, just with one more pair of output transistors on the 545. The GFA-565/GFA-585 is a totally different design from the GFA-5X5.

[@angelescalantegarcia4483]

Seria posible estos tres videos en español?

[@bulwinkle]

I would be interested to see the final cost of this project.

[@phloodpants]

Boards from HoppesBrain.com - $120 Parts to rebuild input board - ~$200 Dead Adcom GFA-585 - $0 to $600 New output transistors, if they are blown - $80 Worst case: $1000 And if you bought the fully assembled boards, that would be $1640 max. That compares very favorably to a new amp in this league. hoppesbrain.com/product/gfa-585-boards/

[@RickMahoney2013]

Sit back, relax and watch the show.

[@3rdaxis649]

I have two of these that I need repaired/reconditioned...

[@russellesimonetta3835]

Were the bad caps IC???

[@sinusshephard5314]

Same with 535II and 545II?

[@MichelLinschoten]

All you commentators have zero clue wtf you’re talking about. The gfa 555 was designed by no less than Nelson Pass for Adcom. For whomever doesn’t get who he is? Perhaps look up Pass labs and Threshold. The gfa555 was not considered high end, it was a design that changed the amplification world as they know it. It was made with a small budget in mind. He exceeded that from an engineering point of of view (he is known for shortest path simplicity build amps) 200watt 8 ohm, 600w full bridged mono and it was a design meant to be minimalistic no dc protection circuit that could taint the sound. Only in severe catastrophic amp failure it would be possible to get dc on the output stages frying speakers. Very and I do mean very little confirmed stories about that Anything after the gfa 555 had nothing to do with Nelson Pass (the 555 is still after 40 years the most desired one due to that fact Nelson designed it) the mk2 was still based on his design but used triple darlingtons what not. Do not confuse the other models for the original gfa555 albeit based on his design. They would still sonically destroy plenty of amps in much higher price brackets. Also the capacitors issue was after the 80ts. These amps when you get them, go for the 555 if you’re serious about it all totally different than this 585

[@JuanLega]

Michel Linschoten the Adcom GFA 5500 also had Nelson Pass input in the design.

[@russellhltn1396]

Interesting. It appears the original boards were single sided, but the replacements are double-sided.

[@phloodpants]

Yes, double-sided boards have become shockingly affordable! They were just too expensive back when the amp was manufactured. Two layers allows me to optimize the layout in many ways... shorter, fatter traces, better trace separation, etc. Solder joint reliability is much better with the plated through-holes versus the filleted joints on a single-sided board.

[@THEtechknight]

So the capacitor plauge dates wayyyyy back then. I remember the period from the late 90s through the mid 2000s, they were horrible.

[@bric7244]

Wow ! Probably just saved me a huge headache. Does this problem happen with the adcom gfa 6000 ? I was just going to buy one ! Thx in advance

[@xraytonyb]

I don't believe the 6000 had this problem. I was mainly with the older model GFA units. For instance, The GFA 555 had the issue, but the GFA 555-II did not seem to.

[@bric7244]

@@xraytonyb ooo ok thank you ,I appreciate your input !

[@ArthurJS123]

While I do enjoy your videos, I have to say, there are a heck of a lot more that can go wrong with electronics than capacitors. I think sometimes their fragile conditions are greatly exaggerated. Not saying that’s the case here, but more often than not, many here on KZbin replace them even when not necessary. Shotgunning capacitors often times is overkill, and not warranted.

[@garybevis8691]

That is not very good advice. Very good, modern capacitors are rated to last 10000 hrs at a given temperature, usually 105°C. That rating delines logarithmically as temperature increases above that rated temperature. 10000 hours is about 5 years. Most commercial electronics has low grade caps and are only rated for 2000 to 4000 hours. That is one or two years and then the failures begin and only get worse with age. These are the facts, you can look them up on any capacitor manufacturers website such as Panasonic, Nichicon, Rubicon or Illinois Capacitor, etc., etc..

[@RickMahoney2013]

There is the Adcom.

[@MrBrymstond]

Tony, you could always go to EasyEDA and recreate a new board and I know this guy changed things when it could have only been inferior components and or copy these boards. You get 10 of these boards for $2.00USD first order. You even have the choice of having silver instead of copper, color, thickness, everything.

[@misterhat5823]

Why re-invent the wheel? Laying out a board is time consuming. Unless this fellow is robbing people on price, there's no point in it.

[@phloodpants]

@@misterhat5823 Yes indeed. I've worked countless hours making these boards as nice as they are, evolving their design, and discarding hundreds of dollars worth of old revision boards. These are not just copies of the original boards. There are many improvements, and the layout is all new, while maintaining physical compatibility.

[@MrBrymstond]

@@misterhat5823 You're absolutely right, why learn anything when someone else in the world already knows, but then he should have purchased the boards already populated with the best components possible as some of the components were hard to find and you may have to sacrifice for subpar components, why re-invent the wheel, it's what we do. We make the wheel better like this guy he purchased the boards from, some of us love to say I did that. Even for our own sake. It doesn't have to get done in a day, it just has to get done. Some of us fools like to learn new trades and some love to play dumb so someone else will just take over and do it for them. I call them leaners. I started off a blue collar worker where everything you see comes from then I had a white collar job, I hated it because they have no respect for blue collar workers until they can't find what they want and they have no clue whatsoever on how to tie their shoes. They didn't like hearing that, the truth hurts, but they used to love having me around. So I stopped fixing their problems.

[@MrBrymstond]

@@phloodpants Like playing guitar in a band, you're never going to just have the idea you want to rock so you go out and buy a guitar and setup a concert. Some learn faster than others and this guy that made that board has some major hit songs under his belt. There's obviously a need for these people and it didn't stop him from re-inventing the wheel and I didn't stop just because I was hearing people tell me I sounded awful, I didn't need to listen to that, I knew it sucked, but over the course of time some if not all of them people would stop everything to show up all over the place just to hear us play.

[@misterhat5823]

@@MrBrymstond Bleh. It's not your choice what someone else does.

[@williamstaten8102]

I collect Realistic stuff and some of them have real bad cap problems. The ones that have problems have a brand called Delcon. Some of my machines are identical models one with elna and the other with Delcon. I've gotton to the point I just change them all out because if one goes bad the rest is soon to fallow. They don't leak out though, just short out.

[@phloodpants]

Ironic. In the Adcoms, it's the Elna caps in the Adcoms that assploded. Good brands are no guarantee against failure! The electrolytic capacitor market is under huge pressure to innovate, and this causes bad electrolyte formulas to be pushed into production, ahead of thorough testing. I avoid using brand-new types of capacitors, preferring those that have been on the market for at least 5 years.

[@goodun6081]

"Shoei" capacitors, if you ever come across them, are bad news. Another thing to consider is, if the polarized capacitor is used in a circuit where it might be briefly exposed to any reverse voltage spukes, it will fail very quickly or perhaps suffer cumulative damage until.it eventually fails. If in doubt, replace with bipolar/nonpolar caps. Feedback caps in the differential amplifier should always be changed to bipolar caps.

[@MichelLinschoten]

It’s simple when it’s old it needs a recap. Stop blaming caps for wearing out that’s what caps do. They wear out, my god dude these amps are well over 3 decades old. They need some love that’s all

[@MichelLinschoten]

Chris Hoppe Adcom doesn’t use Elna as far as I know in their old designs

[@shuntachi]

You forgot to mention GFA-535

[@RickMahoney2013]

There should have been a recall.-

[@robertcalkjr.8325]

Thanks Tony! So, why the love for Adcom? Why would someone want to go through the time and expense for it?

[@JuanLega]

Because you can get one hell of an amp for a fraction of what something similar would cost you now a days.

[@eggshellskullrule7971]

I have a GFA555 II. Great sounding and huge value even at $550 a used stereo piece.

[@MarkTillotson]

Left and right channel pcbs a little bit different from one another - what the hell were the designers smoking!?!

[@phloodpants]

Good stuff I'm sure! It's for physical compatibility. The two boards are mostly mirror images of each other.

[@danielesbordone1871]

I don't want to knock Adcom , but I suspect they were using second or third choice components. Not good.

[@1990notch]

My 585 had elco caps in it.

[@fredoswego]

This video makes me think $300 Adcom amps on ebay are way overpriced.

[@wheeler2581]

char broiled.LOL.

[@Mercury1955]

Yeah I appreciate the video but unless someone has a lot of time on their hands this isn't worth the effort. It's a shame Adcom used the cheapest crappy caps they could find in these amplifiers.

[@RickMahoney2013]

Fried and not Chicken or fish.

[@megamotions]

Très mauvaise qualité de fabrication pas seulement les problèmes de condensateurs il me semble a cet époque la avoir vue des électroniques bien mieux construit et surtout soigné

[@olradguy]

Never liked Adcom, good for catastrophic failure like many other DC to Daylight designs, if I recall they even warned you not to connect/disconnect the input cables with the unit on in the owners manual.

[@goodun6081]

That warning pretty much goes for all power amplifiers, regardless of whether some amplifiers seem to do better at surviving it. Anyway, I have worked on a number of these and similar Adcom models, they're good sounding amplifiers that only very rarely blow up (the fused power supply rails usually act to stop catastrophic damage), and relatively simple circuits, and the only thing difficulty about working on them is if the capacitors have already leaked and caused the circuit board to become conductive. Not to mention the corrosion caused to adjacent parts when the electrolyte hits them.

[@RickMahoney2013]

Thank God I never bought a Adcom.

[@MichelLinschoten]

Rick Mahoney a restored gfa 555 would destroy what you play with unless you spend thousands on some boutique brand. Any other model of Adcom I agree, the original 555 was designed by Nelson Pass and remain highly desirable on the audio market. If you ever get a chance score a 555 mk1 avoid the mk2 and other models. Totally different beast

[@RickMahoney2013]

@@MichelLinschoten Thanks

[@dontcare563]

I don't think ADCOM was EVER considered High End. It kind of reminds me of NAD, they made a good product for the money but High End NO!

[@Chicxulub65M]

Correct Dont Care, ADCOM was referred to as Mid-Fi. similar to NAD, Carver, Rotel, A/D/S, etc.

[@rock3times]

High end is high priced, irrelevant of quality of the sound. Hi fi gears are symbol status for many. To me, what sweet to my ears is what is worthy.

[@eddevito3282]

If you can tell the difference between an adcom amp and a “high end” amp of similar specs with an otherwise identical setup in a blind test, you are kidding yourself.

[@eddevito3282]

Chicxulub65MM if you can tell the difference between any of those amps and a “high end” amp of similar specs in a blind test with otherwise identical setup, you are kidding yourself. In the case of Carver and the magnetic field power amplifier, I’m sure you are aware that his amp precisely matched the signal (using a null technique) of a mark levinson amp at 10x the price and that a panel of reviewers at stereophile magazine could not differentiate between the two in a blind test. When it comes to “high end” , the analogy I draw is to fine hand made Swiss watches like Patek Phillipe at 20,000 vs quartz seiko at 200. The price of the former can be justified on any number of levels including design, the quality of materials, workmanship, etc etc. Just don’t try to tell me it keeps better time.

[@rock3times]

@@eddevito3282 beauty is in the eye of the beholder, same truth with the acoustics... What happen between the ears are. Much better than specs and stats. I love my dynaco ST 70 enhanced with bass from bic america woofer, a pair of psb speakers, a glass of laphroag scotch, and a stick of arturo fuentes cigar. That makes my day.

[@1959Berre]

As far as I can see this amp has some serious design flaws. No protection? Seriously? Suppose you rebuild it. You can be sure it will fail again, hopefully not sooner than later; eventually it blows up a couple of + $1,000 speakers... I would not touch it.

[@CofeeAuLait]

Same here, although you could make your own protection circuit and either adapt/place it outside. ADCOM deserves the thrash bin tho, those boards are made of paper and thin aluminum foil. Very prone to catch fire.