Stevem wrote: ↑Sat Jan 27, 2024 11:29 am
You have a oscillation problem then and likely due to layout reasons.
Just for S & G try reversing the output tube plate wires or the wires off the secondary side of the PT to the speaker jack, whichever is easier for you.
Sorry I didn't fully understand this. I have no nfb if it makes any difference.
I have run the looper and touched everything with chopstick without finding anything. The iron (and components) was stored for a good few years in fairly high humidity, is it worth taking the covers off and looking inside?
Stevem wrote: ↑Sat Jan 27, 2024 11:29 am
You have a oscillation problem then and likely due to layout reasons.
Just for S & G try reversing the output tube plate wires or the wires off the secondary side of the PT to the speaker jack, whichever is easier for you.
I still don't understand this, do you mean reverse the output transformer wires to the plates of the power tubes?
Stevem wrote: ↑Sat Feb 17, 2024 7:12 pm
Reverse the wires from the PI to the grids of the output tubes or the output tube plates to the primary of the Ot.
Seems you overlooked the part where he said, "I have no nfb if it makes any difference."
mike-p wrote: ↑Sun Feb 18, 2024 10:15 pm
Can anyone point me to audio or video examples of acceptable levels of IM distortion in similar amps ie low filtering marshall type amps please?
I mean... all amps, when overdriven, exhibit IM distortion. Here is my favorite example. Alex is repeatably bending a note UP, but you can clearly hear a mirror ghost note going DOWN:
