DC offset - how far apart can the channels be?

[62vauxhall]

The Sony STR-6045 I just acquired (and posted about) has unequal DC offset. There is 13mv on one side and 74mv on the other. Bias current was 12.5mv on both channels but the service manual said 25mv. I adjusted accordingly but DC offset seemed unaffected.

I was under the impression that DC offset was altered by adjusting bias current.

In any case, is the offset disparity cause for concern? The opinions I've read seem to say 74mv is not great but not atrocious. The receiver performed OK with unaltered bias but I've not spent time with it since kicking it up to 25mv. If sound is good and it does not start off throwing off heat, would anyone be bothered about the offset difference?

Despite that I did not do well trying to refurbish a Kenwood integrated, I don't think I'd be against changing the differential transistor pairs. Provided that is I can figure out which new ones would work, I always have trouble with that. And, that critical matching is not essential.

 

[orange]

No, don't go messing around with stuff until you know what the matter is.

If you look on AK you might be able to find Glen's (EchoWars) thread on adjusting DC offset etc.

 

[8991XJ]

EW's thread talks to the need to have the offset low. Sonically, anything under 15 is great, under 50 is fine and over 75 is maybe starting to make the sound not so good. They do not need to match.

I don't think bias is a big mover of the offset.

There is a thread on ak about fixing your issue. The differential pair on one channel aren't as matched as they might have once been and need to be replaced.

http://www.audiokarma.org/forums/index.php?threads/sony-str-6045-bias-and-dc-offset.709212/

 

[laatsch55]

Offset is affected IN MOST CASES by the front differential pair of small signal transistors. Bias adjustments SHOULD NOT affect offset in any significant way. The only downside to excess offset is heat build up in the voice coils of your speaks....DC is BAD for speakers, BUT 74 mv ain't much....

 

[62vauxhall]

That means I shall not be tinkering with it. Thanks!

I'll play with for a couple weeks then probably flog it on CL or CAM. Because of the wood sleeve, I may go on the high side asking price wise.

Kind of wish I had the room to keep stuff like this. It is a very nice looking unit.

 

[laatsch55]

That's about par ain't it??

 

[62vauxhall]

Yup. Count your blessings you live in a house. I used to think I would again one day but nope, ain't gonna happen. Not without winning a lottery anyway. I'd even settle for a second bedroom. I have little reservation letting go of black and grey faced stuff but silver face is just too pretty. I like shiny.

 

[laatsch55]

I count my blessings every day Gary....and thank God I woke up breating fresh air.....