• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Adcom GFA-535 bias question

soundmig

soundmig

AK Subscriber
Subscriber
Does anyone have the proper bias setting for an Adcom GFA-535 (not a GFA-535II)? I saw one post that mentioned +/- 7 mv …. is that correct for the non II version? I did the bias setting on the 535 yesterday. It was set at 17.5mv and was idling hot! I reduced it to 7.2mv and 7.3mv and it is cooler now. But, I'd like verification that this is the correct "range" for the bias setting if anyone has it.
 
Register to hide this ad
Gfa-535

Anyone? Somebody on AK probably knows the correct bias setting for the 535, if you do … I'd love to know :)
 
7mv should be correct for your version as well. As long as the heatsinks are not getting too hot you should be fine. You aren't testing it while connected to a preamp or while floating with no RCA connected are you? The best way to set up the bias is to install an RCA shorting plug in the amplifiers RCA inputs. This ensures that the input signal is held at circuit common. I've seen amps that varied by several mv when the RCA shorting plug was removed and the amp was allowed to float with no connection.
 
I set the bias with the inputs connected as per the GFA-555 service manual instructions (source no higher than 600 ohms - with NO SIGNAL). After the bias adjustment, it is not idling hot and it sounds very good (like and Adcom, clear and clean with a slightly "dry" top end) - so I think everything is OK. I was just taken aback by the bias being set at 17.5mv when I got into it (likely why it was idling hot?), and wanted to make sure that I have the proper setting range. The 555 bias is about 16-17, so maybe somebody before (i bought it used about a year ago) had adjusted it using the 555 spec not realizing the 535 is different? Who knows.
 
Regardless, Mondialfan - thanks for the input I feel better knowing that the 7mv setting "makes sense" :)
 
You must log in or register to reply here.
Back
Top Bottom