ADCOM GFA-555 mod

Lowell_M

Ben or others,
I've only been able to find limited details on the ADCOM mods that are possible. I am trying to understand the shunt capacitor (??) mod a little better to consider if I should give it a shot. :cool:

Skill Level: I have limited experience soldering on a board, but am otherwise perfectly mechanically capable. I used to have a very deep knowledge of electronics, but haven't used it since my senior year in college, so let's consider it almost gone from my brain. But...with some explicit explainations to start with, I'm sure I can ask enough questions to make sure I understand and don't screw things up. :eek::rolleyes:

So... What kind of mods can be easliy done to the GFA-555 and what are the benefits of the mod.

Also... Are the mods easily reversable if I don't like the results?

Thanks:cool:

ben62670

From what I have done the mods are simple on the shunt caps on the big caps. Use a 12uf or so cap on top of the main PS caps. An audio grade cap like the Dayton's is fine. Also you may want to add a 1uf cap in the mix. The big caps are designed to hold a lot of currant. If you add smaller caps the detail is slightly better. Also on the input boards are a few fusible resistors that are not the best for signal path. Shoot me a PM, and I can tell you what resistors to replace. I am going to do the mods myself finally on my own amps. GV27 has pointed me in the right direction concerning replacing signal path R's;)

comfortablycurt

I've been curious about this myself. I'm planning on getting an Adcom 555 in the near future, once my HT is rounded out. I've heard a little bit about the mods that people have done to them, but haven't really been able to find any solid info about them either.

Systems

I think Ben has a schematic so he can tell you if there are any coupling and feedback caps that may need replacing/upgrading aswell.

Ender

Ben, could you shoot me an email about the mods as well? I got a GFA-555MKII a few weeks back that I want to mess with. Lol.

ben62670

GV#27 wrote: »

I think Ben has a schematic so he can tell you if there are any coupling and feedback caps that may need replacing/upgrading aswell.

I have most of the diagrams:)

Ender wrote: »

Ben, could you shoot me an email about the mods as well? I got a GFA-555MKII a few weeks back that I want to mess with. Lol.

You have my number no? Shoot me an email.
Take care.
Ben

heiney9

Also guys.............do a search at DIYAUDIO.com and you will find several long threads on mods for those Adcoms.

ben62670

heiney9 wrote: »

Also guys.............do a search at DIYAUDIO.com and you will find several long threads on mods for those Adcoms.

Thats wheere I learned my stuff;) Again a few naughty resistors, and the cap mods can go a long way. I said it before and I will say it again. Thanks H9 for pointing me in the right direction. NP, and Chris have taught me much!
Ben

Lowell_M

heiney9 wrote: »

Also guys.............do a search at DIYAUDIO.com and you will find several long threads on mods for those Adcoms.

Thanks!