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Thanks loudthud for the suggestions. I was poking around inside the amp last night with a chopstick looking for sensitive areas, and nothing seemed to affect the high pitched tone. So I tried swapping out the 12ax7 with a different one, and what do you know, it eliminated the microphonic feedback. So then I wondered it if was the actual tube, or the way it was seated and after some testing I realized the tube is fine. If I do not have the tube seated in the socket just right it makes the high pitched tone. If I just push it in a bit more or wiggle it, it goes away. I have a spring loaded shield that I installed over my 9 pin, so it will not move much, if at all.
Can anyone help me understand what it is about the tube not seating properly that can cause such loud microphonic feedback? I would just like to better understand what exactly is going on there.
As for the amp, it sounds amazing!!!!!! If I turn the volume all the way up with a guitar plugged in, I can only hear the tiny bit of hum if the room is silent and my ear is within 12 inches of the speaker. If I am further away then 1 foot (normally I'm standing or sitting a few feet away) it is not even audible. The only wire that I might change to a shielded cable to see if it has any effect, is the grid wire from pin 7 running to the volume pot. Out of all the wires, it seemed to be the most sensitive to high voltages, and I think I might be able to cut down the little there is even more.
Thanks again for all the help I have recieved on this forum. I do not think that I could have done it without the knowlede and help from members like loudthud, tubeswell, Bruce, MWJB, martain maning, & Alex R. Now to finish making dovetailed boxes for this champ and my 5E3. I'm thinking for my next project I will take on the Fender Reverb Unit.
Can anyone help me understand what it is about the tube not seating properly that can cause such loud microphonic feedback? I would just like to better understand what exactly is going on there.
As for the amp, it sounds amazing!!!!!! If I turn the volume all the way up with a guitar plugged in, I can only hear the tiny bit of hum if the room is silent and my ear is within 12 inches of the speaker. If I am further away then 1 foot (normally I'm standing or sitting a few feet away) it is not even audible. The only wire that I might change to a shielded cable to see if it has any effect, is the grid wire from pin 7 running to the volume pot. Out of all the wires, it seemed to be the most sensitive to high voltages, and I think I might be able to cut down the little there is even more.
Thanks again for all the help I have recieved on this forum. I do not think that I could have done it without the knowlede and help from members like loudthud, tubeswell, Bruce, MWJB, martain maning, & Alex R. Now to finish making dovetailed boxes for this champ and my 5E3. I'm thinking for my next project I will take on the Fender Reverb Unit.
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