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In Reply to: Re: occasional Distortion...Help! posted by Pär on August 16, 2002 at 04:06:23:
Kiefer,Like Pär sez, rule-out any input overdriving the gain stage. Find a tape deck or CD player which as variable output to the pre-amp. Lower the output volume of the source and see if that eliminate the early distortion.
I'm not familiar with your amp, but if the outlet voltage is 100 VAC, you probably are running the unit at too low voltage. When you crank the volume---the tubes are falling out of the linear range faster, than if the unit was plugged into 118 volts.
More importantly, you run a risk of PS and PT damage---by running a power hungry amp at too low outlet voltage. The amp will suck more and more current to compensate for the low voltage, than the same amp hooked-up to a 188 volt outlet---as you raise the volume. This can lead to overheated PT and PS caps.
Anyhow, this early distortion is famous in guitar amp circles. Guys like Eddie Van Halen would run a Variac between the outlet and the amp. He'd turn the voltage down to get earlier and earlier distortion off his Marshalls. Problem is, he'd inevitably fry transformer(s) and the power supply cap cans.
Follow Ups:
I never, well have rarely listened to my speakers when the voltage gets that low. I usually have to wait till late at night, which sux because I don't want to disturb my neigbors, or in the morning around 10 if I get the chance (the voltage is usually at a decent level till around noon.The problem w/ the distortion is it only pops up every once and a while. I'm goin out of town for a week, but I'm picking up my left channel amp when I get back and can do some more testing (if they never find a problem w/ the amp).
I'm hoping for the best. I guess I'll find out soon enough.
Take care,
Kiefer,Try one more thing... Pull each tube and carefully replace the tube into the same socket. Do this routine a couple of times. You may have a dirty contact between the socket receptors and the pins of the tube.
Hey, it may not resolve the problem, but at least it's a cheap try, Pull and replace each tube STRAIGHT up & down, avoiding bending of the socket lugs and tube's pins.
Hi,Another "freebe" is to swap left right inputs when the distortions sets in.
I still think one can feed it with a distorted signal. Like if the input occationally drops in input impendance or if the feeding unit occationally rises in output impendance. Last case will be rouled out if feeding ICs are swapped. For first look for any caps across the input.Coz distortion is usually the result of impendance missmatch...
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