Input Impedance (think - just a Beginners Question)

[Oliver]

Hi There,

im thinking of building an Overdrive Stompbox using the LM386, which makes a great Job in my LittleGem builded a short Time ago.

Just like the Grace Overdrive or Smash Box, but i like to get one with
Low till Mid Drive - not HighGain Distortionsound.
The LittleGem is Stockbuild and i added a 2.2uF Cap in Series with a 10K
Pot between Pin1 and Pin8 of the LM386, wich makes a Tubescreamerlike
Overdrivesound through a Guitarbox.

Now i like to do that as an Overdrivepedal.

To my question:
is it possible to add an Imput impedance without building an InputBuffer?
Im thinking of Using two Resistors as used for the LPB1 (from Vsource a 47K to the Signalinput and from there a 830K to Ground) will this make Problems

anybody a suggestion for me?

thanx
Oliver

[Rob Strand]

Im thinking of Using two Resistors as used for the LPB1 (from Vsource a 47K to the Signalinput and from there a 830K to Ground) will this make Problems

If I'm interpretting your intentions correctly that won't work how you expect, I'll try to explain.   Adding the *series* 47k  increases input impedance by 47k.  The side effect of the series resistor is that it also decreases the gain, because the input impedance of the following circuit forms a voltage divider with the series resistor (some noise is also added).  The parallel 830k is where I think you have made a mistake, the 830k is in parallel with the existing input impedance, so it has little effect when in parallel with the existing input impedance.