Ugly octave sound

[captntasty]

I've noticed on a Traynor YBA2b that I just recapped a horrible ugly resonance. It is most noticeable on the B string or a B 4th fret Gstring. It sounds like an octave or harmonizer type effect. My research has turned up some posts and info on bad filter caps. As these are all new caps I wonder what else might cause it. There is hum in the amp but it's not bad at all - I have worse hum from any of my SE amps that doesn't interact with the signal at all the way this does. Could it be caused just by component layout? I've tried different cabs, tubes, etc., moving various leads with chopstick like filaments and so forth with no difference or improvement. Any thoughts? Some type of oscillation?

edit: it is a lower octave type note...

[captntasty]

Boy I wish I had a scope! #*(&#$#!

[captntasty]

I guess I've also seen this symptom described as a ghost note or blatt. I've tried most of the things that have been recommended. I wonder if reworking the filter section would be a good idea - perhaps another filter stage?

[Steve Conner]

Most likely one of the new caps you installed isn't properly connected.

What about the bias supply filter cap? If it's bad, disconnected, installed backwards, it can cause the kind of weird distortion you mentioned. It doesn't hum through the speaker, but it modulates the sound. But the first filter cap in a push-pull amp could have a similar effect.

[captntasty]

It turned out to be insufficient filtering. There were originally 2 40uf's in a can and 2 10uf's elsewhere on the board. I had put in a new 50uf/50uf and 2 new 10uf's. I had a feeling it was filtering so I added a dropping resistor between the two halves of the can, a 47uf with additional dropping resistor between the last 50uf and 1st 10uf and moved all the leads to their proper nodes. No more ugliness!