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previous: ken gilbert ok. i'm starting to pursue doing m... -- 5/19/2000 4:21 PM

Re: positive feedback musings...

5/20/2000 4:02 PM
andyfuchs	Re: positive feedback musings... Dynaco's Pas-3 phono preamp used a positve feedback resistor between two 12AX7 stages from cathode to cathode, but also used a negative loop for the RIAA and gain control. It could certainly be done, if used conservatively. The bypass caps on the cathodes is obviously no longer viable. Perhaps treating the input stage of the amp as a "gain block", and not coloring the tone with anything, a simple two tube gainstage could use positive and/or negative feedback to make a nice linear input stage. Since we don't use this stage for overdrive or distortion anyway, audiophile qualities like low noise and low coloration is important.

5/20/2000 4:02 PM

andyfuchs

Re: positive feedback musings...

Dynaco's Pas-3 phono preamp used a positve feedback resistor between two 12AX7 stages from cathode to cathode, but also used a negative loop for the RIAA and gain control. It could certainly be done, if used conservatively. The bypass caps on the cathodes is obviously no longer viable. Perhaps treating the input stage of the amp as a "gain block", and not coloring the tone with anything, a simple two tube gainstage could use positive and/or negative feedback to make a nice linear input stage. Since we don't use this stage for overdrive or distortion anyway, audiophile qualities like low noise and low coloration is important.

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Ken Gilbert btw andy i read your email you sent... -- 5/20/2000 4:16 PM