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Some gain calculations

Posted by Perseo on October 4, 2007 at 08:21:57:

I ran some numbers on the alternatives. I assumed rp of 44k per 6SL7 half, a book value I have seen in real life. I used the mu of 70, although I believe the 6SL7 samples I have tend to run low on mu. Operating point would affect this and I did not figure yours out when doing this.

Your 6SL7 set up: Gain of 28
Bypass the cathode resistor only: Gain of 48
Eliminate the 24uF capacitor between the two 47k resistors (increasing RL to 94000): Gain of 40
Both bypass Rk and eliminate 24uF: Gain of 56

I don't know how important the 24uF may be to limiting PSU noise and ripple, so maybe you compromise with more plate resistance but not the whole 94k, retaining a dropping resistor and the 24uF. Guys below suggest this.