yeah so maybe get amp to stop farting..and check what work and what doesn't
the farty tone is most likely to be the actual circuit design and the fact that it's not voiced for guitar.
the EF86s used in that amp are quite high gain so you're likely overdriving (blocking distortion) each stage putting a guitar through it.
wire up the preamp like an AC30/4 with the single EF86 front end straight into the ECC83 phase inverter - it'll sound killer, trust me.
