Re: 'PC Speaker' Tube Amp

On Mon, 19 May 2008 23:08:15 -0500, flipper <flipper@[EMAIL PROTECTED]
> wrote:

.......snip!......
>
>I'm beginning to get the feeling I could talk till I'm blue in the
>face so a better idea might be for you to pull out RDH4 and read
>Chapter 7, Section 1 (v) "Combined positive and negative feedback at
>the mid-frequency" and  Section 2 "Practical feedback Circuits" (xi)
>"Combined positive and negative feedback."
>
>Figure 7.51a is similar (principle is the same), but not identical, to
>the one I employed . Mine has two less resistors but takes a bit more
>work balancing idle currents and gain.
>
   OK, I pulled that old book out and checked it out, and I see the
light.
  I haven't opened that book for a number of years, but I was
surprised to see how well they covered feedback issues, that dozens of
other engineering texts that I have don't even suggest. 
  In my words, you are generating extra (local) gain using positive
feedback, to increase your (global) loop gain so as to reduce
distortion in another amplifer section (usually the final stage).
  This was an enlightening argument!
Thanks,
-Paul