raybarbeemusic
Member
Having trouble figuring this one out, maybe someone here has some insight. No luck on other forums and I've been working on amps a long time, never exactly seen anything like this. Signal generator won't trigger it so hard as hell to see on a scope.
On Gain channel: When tremolo or speed picking, especially above say an E4, there is a thudding sound behind the pick attack that is almost as loud, and on higher notes louder, than the note. Sounds like (and feels like, through the floor) a double kick drum playing along. The higher the note, the worse it is. Tried lowering coupling cap values throughout the preamp, this helped some but doesn't eliminate it in all situations. Tried switching tubes (JJs are worse due to their big low end response), helps but doesn't prevent it. New power tubes, bias settings, yadda yadda, no joy.
The more bass the guitar has, the worse it is. It might not do it hardly at all on some strats, but on ones with more bass it will, or on LPs, or on bigger strings. 11s aren't likely to trigger it in most cases, 13s will.
Seems like some kind of blocking distortion or feedback somewhere, but damned if I can figure out where.
Clean channel does NOT do this, even with a high gain distortion pedal kicked in, but it will "woof out" a speaker rated at 2x amp power rating, even when moderately loud, if I palm mute a low E. Lowered the coupling cap values from the PI, no real change in that.
Seems like there might be 2 things happening. Some kind of very low end resonance in the power section, and something else in the gain channel preamp.
Anyone heard anything like that before? Ideas?
On Gain channel: When tremolo or speed picking, especially above say an E4, there is a thudding sound behind the pick attack that is almost as loud, and on higher notes louder, than the note. Sounds like (and feels like, through the floor) a double kick drum playing along. The higher the note, the worse it is. Tried lowering coupling cap values throughout the preamp, this helped some but doesn't eliminate it in all situations. Tried switching tubes (JJs are worse due to their big low end response), helps but doesn't prevent it. New power tubes, bias settings, yadda yadda, no joy.
The more bass the guitar has, the worse it is. It might not do it hardly at all on some strats, but on ones with more bass it will, or on LPs, or on bigger strings. 11s aren't likely to trigger it in most cases, 13s will.
Seems like some kind of blocking distortion or feedback somewhere, but damned if I can figure out where.
Clean channel does NOT do this, even with a high gain distortion pedal kicked in, but it will "woof out" a speaker rated at 2x amp power rating, even when moderately loud, if I palm mute a low E. Lowered the coupling cap values from the PI, no real change in that.
Seems like there might be 2 things happening. Some kind of very low end resonance in the power section, and something else in the gain channel preamp.
Anyone heard anything like that before? Ideas?
