Crackle time again

[irish_admiral]

Ok, I've just replaced ALL the preamp tubes in my AD30R with some 12AX7-EH ones, but i'm still getting a crackle (not when I hit the strings, just ambient background crackle) at higher volume settings, especially when the gain dial is turned down low. When gain is high, it doesn't seem to be so much of a problem. The sound is similar to that you get when you turn a pot that is scratchy or dirty.

What do people reckon? Is it the power tubes? Something else?


Don't tell me the best way, just tell me the cheapest way...

[bclaire]

You definitely ruled out the guitar cable?

Otherwise, start tapping the tubes with a pencil or chopstick. It IS possible for a new tube to be defective...

Billy

[irish_admiral]

I have a feeling it's electrical interference as crackling was markedly louder when I had the shields off the preamp tubes.

In any case, I tapped them all with a pencil, and when I tapped them a bit harder I got a quiet 'ding' noise similar to what you get if you flick a round wine glass on pretty much all of them, power stage & all.

Perhaps it's the sockets? Anyone have any advice for cleaning tube sockets?


Don't tell me the best way, just tell me the cheapest way...