Adcom GFA-555 Left Channel Buzz - Page 2

SY · 6th October 2011, 02:45 AM

Quote:

Originally Posted by Zen Mod

is reg common for both channel front ends ,etc.

The reg is not part of the Adcom circuit. That looks like the Kit Ryan regulator from Audio Amateur.

Dudeman, did you try what Nelson suggested? Since he designed that amp, he should know...

Nelson Pass · 6th October 2011, 04:48 AM

It's not a fix - it's a diagnostic tool.

PreCD · 05:02 AM

Nelson,

Yes I understand that. I guess if I would have thought before I asked that question it would have dawned on me that it would work on any amp. Thank you for the reply. I am looking forward to firing up this vintage 86' amp when my 565 gets here tomorrow. I am really tickled that I got one of the early Adcoms that you designed. Everything is still solid except leaching of thermal compound from the rectifier bridges and output boards.

Kevin

turbodawg · 03:47 PM

Bump. I'm having a bit of noise/buzz from the left channel of my original GFA-555. Pretty faint but louder than the right channel and audible in a quiet room from 10 ft away. I bought the amp around 13 years ago, it had one power cap replaced at the time.

I intend to run this pretty hard for PA use in the near future. I'm guessing it would be smart to re-cap the electrolytics, but I'd like to resolve the buzz before dumping time and money into it as a project.

Any guesses if the buzz will get worse as I run the amp hard......?

Zen Mod · 13th March 2013, 04:28 PM

recap

turbodawg · 13th March 2013, 08:54 PM

Quote:

Originally Posted by Zen Mod

recap

So the the recap has a pretty good shot at resolving the buzz? I was going to check the DC offset and adjust the bias for starters. Have downloaded the service manual.

turbodawg · 13th March 2013, 09:25 PM

Sooo.....reading the service manual, it looks like C3 x 2, C5 x 2, and C02, C03, C04, C05......that's pretty easy. I'll get the caps on order tonight.

turbodawg · 02:20 PM

Did some troubleshooting and it's not the amp. Either an issue with my input cables (unusual configuration), EQ, or ungrounded USB interface I'm using. May re-cap in the future but it's a low priority right now.

Zen Mod · 14th March 2013, 02:25 PM

6th October 2011, 05:00 AM	#13
PreCD diyAudio Member Join Date: Sep 2011 Location: USA	Nelson, Yes I understand that. I guess if I would have thought before I asked that question it would have dawned on me that it would work on any amp. Thank you for the reply. I am looking forward to firing up this vintage 86' amp when my 565 gets here tomorrow. I am really tickled that I got one of the early Adcoms that you designed. Everything is still solid except leaching of thermal compound from the rectifier bridges and output boards. Kevin Last edited by PreCD; 6th October 2011 at 05:02 AM.

13th March 2013, 03:45 PM	#14
turbodawg diyAudio Member Join Date: Feb 2004	Bump. I'm having a bit of noise/buzz from the left channel of my original GFA-555. Pretty faint but louder than the right channel and audible in a quiet room from 10 ft away. I bought the amp around 13 years ago, it had one power cap replaced at the time. I intend to run this pretty hard for PA use in the near future. I'm guessing it would be smart to re-cap the electrolytics, but I'd like to resolve the buzz before dumping time and money into it as a project. Any guesses if the buzz will get worse as I run the amp hard......? Last edited by turbodawg; 13th March 2013 at 03:47 PM.

13th March 2013, 04:28 PM	#15
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	recap __________________ my Papa is smarter than your Nelson ! clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM

14th March 2013, 02:08 PM	#18
turbodawg diyAudio Member Join Date: Feb 2004	Did some troubleshooting and it's not the amp. Either an issue with my input cables (unusual configuration), EQ, or ungrounded USB interface I'm using. May re-cap in the future but it's a low priority right now. Last edited by turbodawg; 14th March 2013 at 02:20 PM.

14th March 2013, 02:25 PM	#19
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	__________________ my Papa is smarter than your Nelson ! clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM


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6th October 2011, 04:48 AM	#12
Nelson Pass The one and only Join Date: Mar 2001	It's not a fix - it's a diagnostic tool.

13th March 2013, 09:25 PM	#17
turbodawg diyAudio Member Join Date: Feb 2004	Sooo.....reading the service manual, it looks like C3 x 2, C5 x 2, and C02, C03, C04, C05......that's pretty easy. I'll get the caps on order tonight.

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