Tube DIY Asylum

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RE: Slew rate, TIM hogwwash

Posted by Paul Eizik on July 10, 2017 at 17:46:51:
Gusser

The original post here by Tre' was a request for an explanation from Dennis Fraker concerning a statement Dennis made about common mode effects in amps. The subsequent post by Cris I responded to addressed the request by Chris for information explaining the SET phenomena, and I made a reference to frequency modulation distortion in speakers among other things in my post. As you have stated your comments in the present discussion were in reference to FM distortion in amps. The two things are related but they are not the same thing of course. Otala claimed that FM distortion was audible in transistor amps and he provided data to support this. You seem to be claiming that FMD in modern transistor amps is not audible and you have not supplied any supporting evidence or links for this. When I did a web search to respond to your first "hogwash" post I found some controversy concerning Otala's procedure for minimizing FMD by limiting negative feedback to a certain level in amp stages Otala specified, but I didn't find anything agreeing with your position that FMD has become inaudible in transistor amps. BTW with the post above here you seem to have moved the goal post from the 80's into the 70's, and Otala's first manuscript was submitted in 1976.

Denis is a manufacturer of SET amps and has promoted their use over other amp types. Once again the SET amp craze was introduced to the US through Sound Practices magazine by editor Joe Roberts who was a self confessed solid state Krell high end salesman who was listening to Western Electric speakers (sourced from the ceiling of a shoe store) and powered by a Western Electric 300B tube amp, and he thought this sounded better than what he listened to at work.

I would be interested to read any references you provide concerning the non audibility of FMD in transistor amps with a beginning reference point some time in the 70's as of now. My comments in the present discussion were in regards to Modulation Distortion In Loudspeakers which was the title of a JAES paper by P.W. Klipsch from 1968.

Paul