[Stephie Bench]

Hi John,

Very nice. A couple of comments. On the screen stopper, sometimes you can get a "free" improvement in performance by tailoring the value of the stopper resistor. I think, but I am not familiar with that tube, that a slightly larger resistor may improve the distortion, particularly at moderate power levels. The second comment is the cathode bypass cap. Depending on its overall quality, bypasing that cap with another non electrolytic, say 1 or 10uF polyprop will both improve HF performance, and often lower distortion, since it removes the nonlinear effects of the cap.

Thanks for publishing those.

One further note in general note on low cost SE amps. By using a tetrode or pentode connected in triode (or UL) mode, you often get the benefit of a subtly better (more precisely, lower order) plate resistance linearity. This often doesn't particularly show up in static distortion measurements, but under the condition of a reactive load, it produces lower distortion. Nice benefit from using a "cheap" tube. You can ve4ify this by making your static load reactive somewhat, and measuring the distortion in that condition.

Stephie