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previous: Daver On some schematics I've seen, a res... -- 10/5/2003 11:37 PM View Thread

Re: Resistor Before Coupling Cap?

10/8/2003 3:06 AM
Wild Bill
Re: Resistor Before Coupling Cap?
Daver, I don't believe there's any difference. Whatever the designer thought was convenient, I guess.  
Capacitors have an AC resistance (called reactance) that goes down as the frequency goes up. At a given frequency you have X ohms of capacitive reactance and the value of the fixed resistor. Who cares about the order of 2 resistors in series?  
There can be other factors, I suppose. One would be the Miller effect of the capacitance of the following grid. In effect you'd have a PI or lowpass filter with a C-R-Cg combination. Whether this is significant or trivial in the usual case is beyond me! :) Mr. Aiken has a great FAQ on the Miller effect on his Aiken Amps website. If the effect is to be significant I would expect the values involved to be critical. If the coupling cap was large enough it would probably swamp any audible effect out.  
Just my .02 :)  
---Wild Bill

Daver WB,Thanks. I thought I remember... -- 10/9/2003 12:16 AM