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previous: SpeedRacer Hey all.. hooked up with Trace afte... -- 9/26/1999 12:44 PM View Thread

Re: Marshall Mods / Trace Allen / etc

9/28/1999 4:30 PM
Eth
Re: Marshall Mods / Trace Allen / etc
"All capacitors become inductive as frequency rises, but if we bypass them, with paralell capacitors of smallor value, the composite component can more nearly approximate a perfect capacitor"- Morgan Jones VALVE AMPLIFIERS  
Paralelling capacitors also reduces ESR as an added benifit. Look up a model of dielectric absorption and you will feel like paralelling caps.  
 
Morgan Jones also mentioned that adding too many bypass caps would create inductance at the tie points.  
 
You might want to try this capacitive bypass on cathode bypass capacitors. Cath. caps being larger usually of lesser quality ( higher ESR,d, etc). Also a more dramatic effect might happen, because the C.Bypass cap(s) form a 2nd order rolloff as opposed to the 1st order of coupling caps.  
 
Also Steve Ahola mentioned the practice of biasing a pre-amp tube with a diode, one observation is that a diode almost eliminates (linearizing) negative feedback. (being that the diode causes constant voltage, only changing current...tubes being voltage controlled devices)  

 
Replies:
Trace q{Also Steve Ahola mentioned the pr... -- 9/28/1999 4:48 PM
Mark Knapp Eth,Much better sai... -- 9/29/1999 2:49 AM
Bruce Eth!I'm still waiting for a... -- 9/30/1999 3:20 AM