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Vintage threads from the first ten years

previous: anonymous ok.. so negative current feedback i... -- 11/8/1999 4:43 PM

Re: Advanced feedback loop questions..

11/8/1999 7:37 PM
Stephen Conner	Re: Advanced feedback loop questions.. Hi, The difference in sound is quite large. As you increase the impedance, the bass gets, well I can only describe it as more loose and flubby. The mids get more prominent, and if the speaker was bright already they get very icepick. Overall it seems to me the sound loses clarity and definition. I think too much NFB makes the sound a bit flat and boring though. As a compromise I like to use a low-gain 12AU7 tube in the phase splitter, and only apply about 6dB NFB. You need to use a different phase splitter circuit for the low-mu tube. The Art of Electronics is a great book about electronics in general. There isn't anything in it about tubes in particular. Swapping your negative feedback for positive will cause the amp to be unstable and probably damage it. It certainly won't be very musical. I can't emphasise enough, DON'T BOTHER Steve.

11/8/1999 7:37 PM

Stephen Conner

Re: Advanced feedback loop questions..

Hi,

The difference in sound is quite large. As you increase the impedance, the bass gets, well I can only describe it as more loose and flubby. The mids get more prominent, and if the speaker was bright already they get very icepick. Overall it seems to me the sound loses clarity and definition. I think too much NFB makes the sound a bit flat and boring though. As a compromise I like to use a low-gain 12AU7 tube in the phase splitter, and only apply about 6dB NFB. You need to use a different phase splitter circuit for the low-mu tube.

The Art of Electronics is a great book about electronics in general. There isn't anything in it about tubes in particular.

Swapping your negative feedback for positive will cause the amp to be unstable and probably damage it. It certainly won't be very musical. I can't emphasise enough, DON'T BOTHER

Steve.