In Reply to: RE: The formula: posted by danlaudionut on July 28, 2014 at 09:52:58:
"Sorry it is not that simple ...
You need to take into account the impedance
of the tube section that is in parallel
with the cathode resistor."Dan, you're right!
The formula is, bypass cap value in uf = 1000000/ 6.28 * F3 * r
r = (RK * rk) / (RK + rk) This is what is being bypassed, not just the cathode resistor value. "r" represents the impedance of the cathode itself in parallel with the value of the cathode resistor.
rk = (RL + RP) / (mu + 1)
RK = value of cathode resistor
RP = plate resistance of tube
RL = value of plate resistor (or load that the plate is seeing)
Mu = in circuit Mu of tube
F3 = the 3db down point of the filter
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 07/28/14
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- RE: The formula: - Tre' 10:46:20 07/28/14 (0)