Stoo wrote:
So ..is the fact that the PI is direct coupled to that cathode follower the reason why there is only 1, 1meg resistor in the pi circuit instead of one on each grid?
It's actually because the PI is DC-coupled directly to the stage in front - it doesn't have to be a cathode follower. Take a look at Merlin's example at the bottom of the page on
www.freewebs.com/valvewizard/dcltp.htmlStoo wrote:
Another question about LTPs in general...Is the NFB (on marshall style )coupled to the second grid AND the common cathodes as well? ..that's the way it looks.
Yes, that's right. Most Marshall style amps and a few F*nders inject NFB into the PI at two points. The main NFB is provided by sending the fed-back output signal into the second or 'B' input of the PI. As an option, you can also make the PI appear to be better balanced by injecting some feedback into the PI tail. This was yet another misguided attempt by Leo Fender to make guitar amps sound cleaner.