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Does Adcom make good Amps ?

I'm using a pair of Adcom 565 Mono blocks to power my Maggies. Some of the Adcom amps did have problems with bad caps exploding and ruining the boards. I send mine to Hoppesbrain and had the boards replaced with better boards that he has made. All caps where replaced with bigger and better quality plus a lot of tweaks that he does to make them perform better than new. They are great Amps and have no intentions of giving them up.
 
I’ll revive this thread as I’ve recently become a double Adcom owner.

In about 2001 I bought a new 5300, but I was experimenting with home theater and ended up not using it much. I sold it off years later.

Fast forward to today, I did a lot of reading on these audio sites and decided to take the plunge on a new Adcom 555SE. What a great amp. I’ve tried several different pairs of speakers on it and it’s capable of a holographic sound stage, something I never could achieve with the Parasound A21, though that could have been speaker and cable related. If anyone is thinking about a new Adcom, I can recommend the 555SE without reservation.

The only thing it lacks is a 12 volt trigger, if you’re into that kind of thing.

My current speakers are the Totem Rainmaker bookshelf, a 4 ohm design that the 555 is way overkill with, unfortunately. So I bought my second Adcom, the GFA 6002, rated at 70 wpc, or 100 at 4 ohms, perfect for the musical little Rainmakers.

I should probably say that the preamp is the Parasound P5 and I’ve got Morrow and Audioquest cables throughout. Anyway, the 6002 surprised me! It images just as well as the 555. Instead of bipolar output transistors the 6002 has mosfets, and it also has that 12 volt trigger, gain knobs on the back, and even RCA outputs if you have another amp. It’s bridgeable as well at 175 watts,

Quite a nice package, Adcom sells them on its site, or the Adcom-USA.com site. I got a b stock for 399. Anyway, in my experience, Adcom still makes a great amp. I like Parasound, but imho, you really don’t have to spend that kind of money on an amp.
 
I've owned an first generation 555 since 84. I had it modified at Musical Concepts to top level modifications and it sounded like a very warm tune amp with awesome low level detail. I know the newer Adcom amps are mosfet which has made them more easier on the higher registers. My adcom has been a workhorse although I replaced it with a pair of Plinius mono blocks.
 
Low level detail. That’s a great aspect that I don’t typically listen for, but yeah, I like the low level detail of these adcoms.

The newer Adcoms did move to mosfets, but with all of Adcom’s current line up, they’ve moved back to the old design of Nelson Pass. No mosfets in the amp stage.

To be honest, I like both in my current set up..
 
runnin' said:
Low level detail. That’s a great aspect that I don’t typically listen for, but yeah, I like the low level detail of these adcoms.

The newer Adcoms did move to mosfets, but with all of Adcom’s current line up, they’ve moved back to the old design of Nelson Pass. No mosfets in the amp stage.

To be honest, I like both in my current set up..
Click to expand...

I was just over at adcom's site and the new GFA-555se looks quite nice for the price.
 
I have a GFA 555ii driving my Kef R107s and it sounds excellent. I'd probably have to spend a lot of cash to better it.
The OP's concern regarding the lack of speaker protection exists in many of the better amps. The Adcom circuitry does not have any coupling capacitors between the amplification stages to protect against a DC current surge, which is the same design as Pass, Levinson, and Krell. Instead, they use DC servos, which would have a minmal effect on controlling a surge in DC current, but also doesn't add complexity to the circuit, so the sound doesn't suffer. So really, that's a good thing, and one of the reasons the Adcoms perform as well as they do.
As far as a DC overload being introduced to the amp's inputs, and then being amplified and destroying your speakers (which is, of course, a possibility); the most likely source of that DC would be a tube preamp. But tube preamps, by design, have coupling capacitors in the output stage, which would protect against the preamp from delivering a large dose of DC current to the amplifier.
The key here, especially if one has purchased a used tube preamp, would be to make absolutely sure that the coupling caps in your pre are of a good quality, and are also in good shape, like, not too old.
This should look after your concerns regarding the safety of your speakers, as most good amps are probably going to have this type of unencumbered circuitry.
The other really nice thing about the 555ii, is the beefed up power supply. It will drive almost anything, right down to 2 ohm loads.

Dave
 
david1111 said:
I have a GFA 555ii driving my Kef R107s and it sounds excellent. I'd probably have to spend a lot of cash to better it.
The OP's concern regarding the lack of speaker protection exists in many of the better amps. The Adcom circuitry does not have any coupling capacitors between the amplification stages to protect against a DC current surge, which is the same design as Pass, Levinson, and Krell. Instead, they use DC servos, which would have a minmal effect on controlling a surge in DC current, but also doesn't add complexity to the circuit, so the sound doesn't suffer. So really, that's a good thing, and one of the reasons the Adcoms perform as well as they do.
As far as a DC overload being introduced to the amp's inputs, and then being amplified and destroying your speakers (which is, of course, a possibility); the most likely source of that DC would be a tube preamp. But tube preamps, by design, have coupling capacitors in the output stage, which would protect against the preamp from delivering a large dose of DC current to the amplifier.
The key here, especially if one has purchased a used tube preamp, would be to make absolutely sure that the coupling caps in your pre are of a good quality, and are also in good shape, like, not too old.
This should look after your concerns regarding the safety of your speakers, as most good amps are probably going to have this type of unencumbered circuitry.
The other really nice thing about the 555ii, is the beefed up power supply. It will drive almost anything, right down to 2 ohm loads.

Dave
Click to expand...
The Walt Morrey 5#5-2 amps do incorporate a DC blocking film cap at the input, otherwise the amps are dc coupled through with servo offset correction as noted. The input blocking caps are good practice for general use as some sources may put out a dc offset. Something the earlier Nelson Pass amps cannot handle gracefully.
 
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Hi Pio. So does that mean that my speakers are protected a little more than I thought? That would be somewhat comforting, as I didn't think there was really any protection, and just hoped the coupling caps i my pre didn't fail.
 
david1111 said:
Hi Pio. So does that mean that my speakers are protected a little more than I thought? That would be somewhat comforting, as I didn't think there was really any protection, and just hoped the coupling caps i my pre didn't fail.
Click to expand...
Yes, from an input offset fault. For the nervous, an aftermarket offset detecting disconnect module is available somewhere as a kit. I don't use it on any of my own amps, fwiw, but I don't leave them connected live unattended either.
 
That's great. Thanks for the info. I won't bother with any extra protection, I'll just make sure my tube pre is well maintained.

Dave
 
david1111 said:
Hi Pio. So does that mean that my speakers are protected a little more than I thought? That would be somewhat comforting, as I didn't think there was really any protection, and just hoped the coupling caps i my pre didn't fail.
Click to expand...
The major concern with the older Adcom amps is that a servo, or an output transistor failure could send a lot of DC to your speakers, potentially causing quite a bit of damage to them, before it blew a rail fuse.
Fortunately, they don't seem have output failures very often.
 
I find the chronic harping on the ''LACK OF SPEAKER PROTECTION!!! :yikes:'' with regards to Adcom amplifiers to be both tiresome and indicative of an overall lack of technical experience and expertise.

There is nothing different in the design of the Adcom 5xx series of amplifiers from any other high-powered SS amplifier that would cause it to be any more dangerous to your speakers well being than any other manufacturers similar offering from a similar time period.Period.

The designs are well thought out,and used high quality semiconductors.Most failures are/were caused by abuse and nothing else.Stupid is as stupid does.

However you care to do the math,more speakers have gone up in flames (often literally!!) at the hands of Crown (Amcron in Canada),BGW,Phase Linear and Dynaco power amps (most models of which ALSO HAD NO SPEAKER PROTECTION whatsoever) just to name some well-known types, than have ever been damaged by Adcom amplifiers,just based on the sheer manufactured quantities of these other brands of amplifiers.

I truly wonder how many documented cases of speaker damage (in a home environment,the intended use of these units) actually exist......
 
I've worked on the Adcom line for over 30 years, there have been several amps that have passed rail voltage to destroy speakers. The GFA 565 in this case, I have documented at least 14 units over that time001.JPG 009.JPG
 
The 565 that destroyed that speaker did not have any leaking lytics, Just one, yes one resistors opened up on the VAS that led to >60vdc to the speaker. They are good sounding amps and most work fine up till the day they fail then it's all over except for the tears. You can argue that there are other amps with NO protection and yes the same thing can happen as this example. Lesson learned, either incorporate a dc protection circuit or get another amp that has one. The movie Deer Hunter comes to mind.
 
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