Update: Have been using the amp every night since 2-12-2023. It gets a little warm after an hour. So far so good with the speaker switching system. I need to add a woofer to the 802s, they are a bit bass shy.
I will add there are some Beatle songs that sound amazing. I had forgotten all the glory of the system
Here, There, and Everywhere
Come Together
If I Fell
Hey Jude
1st Piano Concerto Tchaikovsky a recording with Lang the pianist
I hear that the speakers should also be refurbished, but I see no faults.
I will add there are some Beatle songs that sound amazing. I had forgotten all the glory of the system
Here, There, and Everywhere
Come Together
If I Fell
Hey Jude
1st Piano Concerto Tchaikovsky a recording with Lang the pianist
I hear that the speakers should also be refurbished, but I see no faults.
That all sounds normal to me, your amp is probably fine. There's no such thing as zero risk, and if you're into hi-fi and you never blow anything up, are you really having fun? The GFA-555 has very little to go wrong with it.
For all the worries about capacitors blowing up amplifiers, it's not usually the capacitors that cause a speaker-blowing faults like "going DC". I'm not talking about Adcom specifically, just amps in general, in my experience. (The Adcom GFA-565 being a noteworthy exception, it's capacitor leakage does cause DC)
There's not many electrolytic caps in a GFA-555 anyways. There's one in the bias spreader, very unlikely to cause a problem even if it does go bad. There's some power supply bypasses on the output modules, again you might not even notice if they went bad. And there's two filter caps for the servo op-amp power supply. And the main supply filters. If those go bad you'll probably start noticing a hum. The main filters almost never go bad.
Most of the GFA-555's people send me to refurbish are actually working fine. The blown-out GFA-555 MKII's that I have seen have usually been due to one of two things.
1. VAS transistor shorted, either due to overheating, (Likely from poor ventilation) or from it's solder joints getting cracked from thermal cycling. (Again probably due to poor ventilation.)
2. Shorted outputs. Usually due to accidental short-circuits like stray speaker wire strands.
You can re-flow those solder joints and install a small heatsink and you'll never have that problem. It only needs to be a small heatsink, don't over-do it.
Some of this is in my FAQ, and I might add some text from this post to it.
https://hoppesbrain.com/adcom-faq/#What-are-the-most-common-issues-with-the-GFA-5x5
Personally I'd be more worried about the caps in the 802's. Electrolytic crossover capacitors are actually more problematic in speakers than they are in powered devices. The capacitors sit there with 0VDC on them for a long, long time, and the oxide layers degrade without occasional bias. They tend to drift upwards in value, and also upwards in ESR. I have a pair of Matrix 805 that had that issue. I replaced the caps with polypropylene, and that worked out well, but I think the 802 has some large-value electrolytics in there. They can't always just be swapped for poly caps, due to the ESR being so much lower... The electrolytics B&W used are low-ESR types (for an electrolytic) and it may be hard to find a modern equivalent. The ESR affects the crossover points, poles and slopes. A whole can of worms there...
For all the worries about capacitors blowing up amplifiers, it's not usually the capacitors that cause a speaker-blowing faults like "going DC". I'm not talking about Adcom specifically, just amps in general, in my experience. (The Adcom GFA-565 being a noteworthy exception, it's capacitor leakage does cause DC)
There's not many electrolytic caps in a GFA-555 anyways. There's one in the bias spreader, very unlikely to cause a problem even if it does go bad. There's some power supply bypasses on the output modules, again you might not even notice if they went bad. And there's two filter caps for the servo op-amp power supply. And the main supply filters. If those go bad you'll probably start noticing a hum. The main filters almost never go bad.
Most of the GFA-555's people send me to refurbish are actually working fine. The blown-out GFA-555 MKII's that I have seen have usually been due to one of two things.
1. VAS transistor shorted, either due to overheating, (Likely from poor ventilation) or from it's solder joints getting cracked from thermal cycling. (Again probably due to poor ventilation.)
2. Shorted outputs. Usually due to accidental short-circuits like stray speaker wire strands.
You can re-flow those solder joints and install a small heatsink and you'll never have that problem. It only needs to be a small heatsink, don't over-do it.
Some of this is in my FAQ, and I might add some text from this post to it.
https://hoppesbrain.com/adcom-faq/#What-are-the-most-common-issues-with-the-GFA-5x5
Personally I'd be more worried about the caps in the 802's. Electrolytic crossover capacitors are actually more problematic in speakers than they are in powered devices. The capacitors sit there with 0VDC on them for a long, long time, and the oxide layers degrade without occasional bias. They tend to drift upwards in value, and also upwards in ESR. I have a pair of Matrix 805 that had that issue. I replaced the caps with polypropylene, and that worked out well, but I think the 802 has some large-value electrolytics in there. They can't always just be swapped for poly caps, due to the ESR being so much lower... The electrolytics B&W used are low-ESR types (for an electrolytic) and it may be hard to find a modern equivalent. The ESR affects the crossover points, poles and slopes. A whole can of worms there...
Hoppe's Brain:
Thanks so much for your words. So far the amp has been working fine; I used it every day. It is very quiet with zero hum. I do know guitar amps hum when the caps are bad. In any event the amp is 33 years old, but I did not used it regularly for many years---sometimes 2-3 times a year. Nevertheless, I would assume the amp is aging. When I power off the amp I hear I hear a very very very low frequency wooosh that last a second or less.
I also have the ADCOM power conditioner and pre-amp with a tuner, so far so good.
The B&Ws are also 33 years old and they were used more often as they were attached to the AV receiver in the TV room. I note they do not have a lot of bass response and I used them with a woofer. I opened the speaker and the caps seem to be large and there are copper coils in the circuit. I assume they are OK, but I could take them to a guy in this area. that refurbishes old speakers.
Thanks so much for your post. This has given me a lot of confidence about the amp. BTW, mine was built in America. I don't know if that makes a difference.
Thanks so much for your words. So far the amp has been working fine; I used it every day. It is very quiet with zero hum. I do know guitar amps hum when the caps are bad. In any event the amp is 33 years old, but I did not used it regularly for many years---sometimes 2-3 times a year. Nevertheless, I would assume the amp is aging. When I power off the amp I hear I hear a very very very low frequency wooosh that last a second or less.
I also have the ADCOM power conditioner and pre-amp with a tuner, so far so good.
The B&Ws are also 33 years old and they were used more often as they were attached to the AV receiver in the TV room. I note they do not have a lot of bass response and I used them with a woofer. I opened the speaker and the caps seem to be large and there are copper coils in the circuit. I assume they are OK, but I could take them to a guy in this area. that refurbishes old speakers.
Thanks so much for your post. This has given me a lot of confidence about the amp. BTW, mine was built in America. I don't know if that makes a difference.
No worries about the whooshing sound when it powers off! Totally normal and doesn't indicate any deterioration. Every Adcom has its own personality in this regard. Some make a squeak, or a fart or a bup-bup-bup... Some make no sound at all. But it's just what happens when the voltage in the circuit gets too low for the feedback to work anymore and it gets all wobbly, each in its own way.
But this is why amps always have relays these days. Many amps make these sounds on shutdown, you just don't hear it because the relays clicks out as soon as you hit the power button.
But this is why amps always have relays these days. Many amps make these sounds on shutdown, you just don't hear it because the relays clicks out as soon as you hit the power button.
Yeah, I would! At least replace the electrolytics with similar, low-esr bipolar electrolytics. I don't know which caps to recommend but I'm sure that's been discussed ad nauseum.
You'll probably find some other little details like loose screws, tired gasket foam, etc... Taking apart an old speaker, you always find things that need a little attention.
You'll probably find some other little details like loose screws, tired gasket foam, etc... Taking apart an old speaker, you always find things that need a little attention.