View Full Version : SS bias pot tweaking


superampman
21-03-10, 10:11 AM
I'd love to hear a good argument against the practice of adjusting the bias on your SS amp while listening. Every time I bring it up I get beaten with a big stick even though I've never in about 30 or so years been zapped doing so. Is there " anybody out there" who is like- minded and sees the efficacy in this procedure? I've found it's the only way to match them with pin-point accuracy.

Regards

superampman
22-03-10, 03:08 PM
"something is happening here but you don't know what it is, do you, Mr. Jones".
Regards,
Pete

nathandegraaf
04-04-11, 11:14 AM
And we look at the television...

Robert
04-04-11, 11:56 AM
I'd love to hear a good argument against the practice of adjusting the bias on your SS amp while listening. Every time I bring it up I get beaten with a big stick even though I've never in about 30 or so years been zapped doing so. Is there " anybody out there" who is like- minded and sees the efficacy in this procedure? I've found it's the only way to match them with pin-point accuracy.

Regards

There is a point for any given SS circuit where distortion sinks to a minimum depending on the quiescent current. Ears aren't good enough to set this unless the amp in question is of very poor performance. You need to measure the amplifier while making the adjustment for best results.

Having said that, most circuits perform well enough if you get within a target range so you can usually just follow the service manual.

martin clark
04-04-11, 12:08 PM
And if you turn it up too high, you can cook the amp in fairly short order.

Anyway - here's a worked example which makes Rob's point. Note how small the numbers are, even for such a simple amp:

http://www.pinkfishmedia.net/forum/showthread.php?t=36057