Ghost notes or what? (video)

[jussi]

My amp is making a loud and bassy sound when I play a certain note if I use loud volume. I've tried to repeat it with another amp and same cabinet but it didn't happen so I guess the problem is in the amp.

I've never experienced ghost notes before so I'm not sure if it's one. Here is a video of me playing the amp. At 09:25 you can hear very well the undernote:
Doom/sludge guitar amp - YouTube

I have no idea how to start debugging this.

My layout looks like this: http://www.2ty.in/14xfq

[MarkusBass]

The layout is very nice but the schematic would help much more. I don't have that much time to wait until 9:25 to hear the problem but it's clear that there is some mistake in the amp. Simple method to find out what is the problem is to use a signal generator and an oscilloscope and check "sub-circuits" of the amp (separately). I mean the power amp and the preamp. It can be a simple problem like oscillations, or incorrectly connected wires, or incorrectly connected output transformer. Without the schematic and some checking it's hard to tell.

Mark

[Jazz P Bass]

Do Any controls affect the problem?