buffer help

[nognow]

is there a way to add a gain adjustment pot to the following buffer?:

[ashcat_lt]

Yep!   

Put the pot as a variable resistor in place of the jumper under the opamp.  Put a resistor in series with a capacitor from the left side of the second row down (pin 2 of the opamp) to ground somewhere.  Or swap the resistor and pot.  The form a voltage divider (google it), the inverse of the voltage divider ratio is the gain of the circuit for frequencies which pass the cap.  The values are almost arbitrary, except that the cap should be very big to pass as much of the guitar spectrum as possible. 

You really should have maybe a smallish resistor in series with 9V going to the board, and a big cap from 9V to ground, and another relatively large cap rom where the 10Ks meet (the bottom row) to ground.  Not quite such a big deal if you're only running off battery, but if you're going for a wallwart...Actually, a diode in series with the resistor from 9V would be nice for reverse polarity protection also.

[nognow]

is there a way to add a gain adjustment pot to the following buffer?:

should I do all three things you've listed in the first paragraph or just one?
what do you mean by "the board"? and what would you consider a "smallish resistor" and a "big cap"?

Thanks

[ashcat_lt]

should I do all three things you've listed in the first paragraph or just one?

You need to make a voltage divider between opamp's output and the inverting input.  That means you need one resistor between the output and the inverting input, and one from the inverting to ground.  There needs to be a cap between the inverting and ground.  In order that it be adjustable, one of the resistors needs to be variable (the pot).  Actually, it's a heck of a lot less messing around if the pot is the one between output and inverting, else you'll never get down to unity, and you'll need another resistor to keep it going toward infinity, so, that's what I'd probably do.

what do you mean by "the board"?

The piece of perf upon which you are building.

and what would you consider a "smallish resistor" and a "big cap"?

IDK, like 100R seems reasonable.  For the power supply, go like 100uF or so.  For the cap to ground from the inverting input, it  kinda depends on the value of the resistors you're using, but 10uF is more than big enough for reasonable values.

Operational Amplifier - Non-Inverting Amplifier apres wiki