[sdiy] Volume control help

[Harry Bissell Jr]

OOhhhh I know

Its to stop a huge DC thump when the cable is plugged
in hot.  Keeps the output side at ground potential...
preventing a sudden DISCHARGE through the input
impedance of the following stage :^P

H^) harry

--- WeAreAs1 at aol.com wrote:

> 
> In a message dated 7/6/05 12:37:30 PM,
> music.maker at gte.net writes:
> 
> << One thing to try is to replace the one meg
> resistor (R14)
> with a one meg pot used as a voltage divider.  That
> way, all
> of the expected impedances are what the circuit
> expects.  >>
> 
> Hello Scott and Mikael,
> 
> I don't quite understand the purpose for R14 (the
> 1Meg resistor to ground at 
> the output).  Can you explain?  Is it there to
> protect against potential DC 
> voltages (pun unintended) the mixer might encounter
> in the nasty real world of 
> DIY guitar stomp boxes?  It does form a mild
> high-pass filter with C5, but I'm 
> not sure such a filter is even needed at that stage
> (and at that Fc).  Even 
> with the 1Meg, the Fc of that highpass filter could
> be affected by plugging the 
> mixer into an unexpectedly low-impedance
> destination.
> 
> BTW, I think a good solution to the master volume
> problem might be to wire 
> that 10K pot as a voltage divider between the two
> opamps.  You would use the 
> same kind of voltage divider that Mikael described
> before -- basically, just like 
> those input volume controls at R1 through R4.  The
> pot would be connected 
> between Pin 1 of ICa and R10 (100K resistor).  That
> way, the second opamp should 
> be unaffected in its purpose as an inverter and
> output buffer amp, and that 1 
> Meg resistor at the output can continue doing
> whatever it's supposed to do, 
> unimpeded (OK, that one was intended).
> 
> Michael Bacich
> 
>