Pesky capacitor; Guitar example

[haandruss@xxxxxxx (Harvey A. Andruss, III)]

I did some re-reading in the _Guitar Handbook_ by Ralph Dreyer (no BSEE
needed :):).  FJM is probably right about this being a treble bypass
circuit, since this is done with guitar wiring all the time (thanks for the
use of your CAD system, Rocket Rick :) :)

CTI's comeback doesn't really make sense since even though a larger volume
pot would certainly make it 'less loud' throughout more of it's range, but
'full on', or nearly so would be the be equivalent to the regular pot
(right?).

The single guitar pickup example:

                   -------|  |-------
                   |       C2       |
                   |                |
       -----------------/\/\/\/\---------Vout(to amp)
       |      |            R2a      |
       |      = C1                  /
     -----    |                     \
     | X |    \                     / R2b
     -----    /  R1                 \
       |      \<---|                /
       |           |                |
       ----------------------------------Ground(shield)

X = 3K to 14 K at DC (w or f --> 0)

 3K represents the single coil w/lotsa twang and hi freq components, but
less volume;
14K represents the humbucker w/lotsa warmth, less high freq components,
more volume

R1 = 0 to 500 K log for passive tone control
R2a + R2b = 500K log for volume control
C1= 0.02 mf (lower gives you more tone affect from R1)
C2 = 0.001 mf

So I bet it's a pretty small capacitor, but what is X for a crystal element
itself (10 or 100 K)?  I get 318 Hz for f (3 db break) in this circuit (did
I do that right, seems too high,as does Rick's 100 Hz?)  Other comments?

============================================================================
=============

Reference what Rocket Rick Barker offered to the list on Wed, 26 Oct 1994
21:15:46 -0500:

>>The capacitor is in paralell with the potentiometer.  It seems to me that
>>if the potentiometer wasn't wide open the capacitor would pass the high
>>frequencies on through. Could it be that's what it's for. To boost the
>>highs at lower volume?   Just a theory.  FJM
>
>Not on mine(but maybe it's hooked up wrong). It's wired in parallel with
>the input side of the pot and the wiper. Here's the circuit(notice the
>lovely CAD system):
>
>              -------|  |-------
>              |        C       |
>              |                |
>       ------------/\/\/\/\--------------------Vout(to amp)
>       |              R1            |
>       |                            /
>     -----                          \
>     | X |                          / R2
>     -----                          \
>       |                            /
>       |                            |
>       ----------------------------------------Ground(shield)
>R1 + R2 = 500K
>
>When the mic is turned down all the way, R2=0 and Vout is at the same
>potential as ground.
>When the mic is turned all the way up, R1=0 and the
>cap is shorted. So in both extremes, the cap is out of the circuit. Also,
>an RC network in this configuration acts as a high-pass filter -
>essentially passing everything except sub-100HZ. This is what led me to
>believe it was there for smoothing out transients.




Regards,
Harv       haandruss@xxxxxxx - opinions my own