See https://www.tdpri.com/threads/plexi-clone-build-cannot-figure-out-why-harsh-distortion.1044918/ for my last thread on this. Following the last thread, I basically started from close to scratch, and rebuilt from the ground up to try to make my build much cleaner, and hopefully get rid of the harsh distortion. New PT, new OT, new choke, all new board components (but same board), (some) new filter caps, better grounding scheme, tried to do better wire routing and lead dress all around. Aaaaannnd.... It sounds mostly the same. Still have those weird overtones... Furthermore, the tubes are still getting really really hot, and occasionally the HT fuse blows. This really makes me think there's parasitic oscillation happening somewhere, burning too much power and making the output tubes work too hard. Here are some images of the new build: Input section: Potentiometers and post-PI section: Power section: Filtering section: Output section: Preamp section: Side view: Other side view: Other side view: Final side view: LMK if there's anything you want to see in more detail, or if you have suggestions on anything that could be better. I met up with someone on the forum, and we started running some signals through the amp and seeing how it looks on the oscilloscope. A lot of weird results, which I'll post about in a bit.