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Does Adcom make good Amps ?

PabloTincho said:
Is the 545 mk2 the best sounding adcom amp ? Also is just only class A

what do you make about their number ?
https://www.kenrockwell.com/audio/adcom/gfa-545-ii.htm
Did you guys see this ?
https://hoppesbrain.com/2016/03/18/a-custom-gfa-545-ii-with-an-insane-power-supply/
Click to expand...

I have heard some people say that they like the smaller amps like the 535 and 545 but the only ones I have listened to are the 555ii and 5800 so I don't have an opinion. Neither one has been used in a critical application either although I may redo my bedroom with better speakers this weekend.
 
PabloTincho said:
What do you guys make of the 545 mk2 ?
I have one that is working fine but thinking about a full recap
Click to expand...

The 545/545 II is a good solid performer and supplies a fair amount of power if you don't have too difficult a load. I might just have a tech check it out to if it is in spec before I would spend the money for a recap. If it is in spec then I would leave well enough alone.
 
PabloTincho said:
Is the 545 mk2 the best sounding adcom amp ? Also is just only class A

what do you make about their number ?
https://www.kenrockwell.com/audio/adcom/gfa-545-ii.htm
Did you guys see this ?
https://hoppesbrain.com/2016/03/18/a-custom-gfa-545-ii-with-an-insane-power-supply/
Click to expand...
Class AB. The Mk-II series Adcom amps were by Walt Morrey and addressed some shortcomings with the earlier Nelson Pass designed series in parts quality and construction.
The 5000 series Adcom are MOSFET amps by Nelson Pass, some consider them best but opinions vary.
 
PabloTincho said:
Is the 545 mk2 the best sounding adcom amp ? Also is just only class A

what do you make about their number ?
https://www.kenrockwell.com/audio/adcom/gfa-545-ii.htm
Did you guys see this ?
https://hoppesbrain.com/2016/03/18/a-custom-gfa-545-ii-with-an-insane-power-supply/
Click to expand...

The Adcom 5xx series are not Class A. They are Class AB. Folks who's ear I trust have said the GFA-53x series are the best sounding of all Adcom amplifiers.

FWIW: I have two MK-II GFA-545's. They are used to bi-amp a pair of Acoustat Model 1's and Acoustat PSW-1 (passive sub) along with an electronic crossover. The Model 1's are my surround speakers.
 
JoeESP9 said:
The Adcom 5xx series are not Class A. They are Class AB. Folks who's ear I trust have said the GFA-53x series are the best sounding of all Adcom amplifiers.

FWIW: I have two MK-II GFA-545's. They are used to bi-amp a pair of Acoustat Model 1's and Acoustat PSW-1 (passive sub) along with an electronic crossover. The Model 1's are my surround speakers.
Click to expand...

FWIW and this is not directly related to the question asked, the GFA-5800 is apparently true Class A up to 10W output power. I was just reminded of this little fact last night while looking for the service manual for it.

I don't know at what point exactly the GFA-535/45/55 stops being true Class A but I am assuming it is lower as 10W is quite high for a Class AB amp.
 
N8Nagel said:
FWIW and this is not directly related to the question asked, the GFA-5800 is apparently true Class A up to 10W output power. I was just reminded of this little fact last night while looking for the service manual for it.

I don't know at what point exactly the GFA-535/45/55 stops being true Class A but I am assuming it is lower as 10W is quite high for a Class AB amp.
Click to expand...

I've read about amps that are class A for the first few watts and then transition to AB. How is this done? If the bias is high enough for class A at low power, how does it stop?
I am asking a serious question/s, I have not been able to find anything that explains this.
 
I would even say a very good amp. Are they excellent or superior amps and on the cutting edge?NO. Are they as good as a Hafler in some ways? Yes, sonically no. Do they match a Krell or Bryston for instance? The answer is even a bigger No. They are just a very good and satisfying with the right speaker. They can sound bad with some great speakers too. But whose fault is that? the Speaker or the Amp? They always meet specs if restored properly and when new is all I know.
 
Pio1980 said:
Class AB. The Mk-II series Adcom amps were by Walt Morrey and addressed some shortcomings with the earlier Nelson Pass designed series in parts quality and construction.
The 5000 series Adcom are MOSFET amps by Nelson Pass, some consider them best but opinions vary.
Click to expand...

+1 for @Pio1980 comments.

Years ago I had the triple 5 mk1 and mk2 versions. They are good for what they are but they are not a Krell MDA or ML 20.6.
 
PabloTincho said:
What do you guys make of the 545 mk2 ?
I have one that is working fine but thinking about a full recap
Click to expand...

I just did a partial recap on a 545 (not a mk2). Didn't replace the large PS caps, only the smaller electrolytics. There were only 4 caps total. Worth the effort.

Also adjust the bias while you're in there.
 
TPettenati said:
I just did a partial recap on a 545 (not a mk2). Didn't replace the large PS caps, only the smaller electrolytics. There were only 4 caps total. Worth the effort.

Also adjust the bias while you're in there.
Click to expand...
A worthwhile mod on the three mk-1 series is adding 47uF/160vdc elyticaps to the + - driver board rails after the fuses, which should be changed to ceramic types of the same rating.
Also, put a heat sink flag on the bias transistor.
 
I had an Adcom GFA-535, the one Sam Tellig raved about. It did a great job with a pair of Acoustat electrostatics, but my Apogee Slant 6 sounded so much better with a Marantz 250, and after the Marantz blew itself up a McCormack DNA 0.5 Deluxe, and then even better bi-amped with a B&K 5 channel AV5000.

If the Acoustats had been mine, I might have kept the Adcom.
 
I worked at an audio shop that sold Adcom. My first real amp was a GFA-545 which I was very happy with. I also won a GFA-535II in a sales contest which I still own today and use as a lab amp or occasional backup. That little amp has been flawless. I also think the '535II sounded better than the bigger GFAs of the time. hoppesbrain.com sells power supply upgrade kits which I've thought about buying for a long time but I have enough projects going right now. I generally try to update power supply caps once an amp gets to be 30 yrs old.

I sold a ton of these amps back in the day. They were reliable, sounded decent, and for the price they were hard to beat.
 
I have a completely rebuilt GFA-555, and it is an amazing amp... dynamic and musical, that exhibits great control over the speakers. I am very happy with it. :)
 
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