how do I set op-amp gain?

[any]

Mayebe I've overlooked something totally obvious, but using the search function
and looking into the stompbox wiki I couldn't find an explanation as to how I can set
the gain of an op-amp.

In my example I actually need to know if I can also lower the gain or output volume.
I've built a PWM (from circuit snippets) but with a passive volume control I loose
an incredible amount of Bass when I turn the volume down. (And I'm using it on bass guitar)
So I've placed a simple buffer between the pwm and the volume pot, but now even a 1k
pot is not small enough to get a good range on the dial.
So I figure I need to either lower the gain or the output of the op-amp or ask you for other clever idea's! 

[Seljer]

well you have 2 common implementations of an opamp as an amplifier

http://en.wikipedia.org/wiki/Operational_amplifier_applications#Inverting_amplifier
http://en.wikipedia.org/wiki/Operational_amplifier_applications#Non-inverting_amplifier

its also described in here http://www.generalguitargadgets.com/richardo/distortion/index.html

[Mark Hammer]

On my site (hammer.ampage.org), around page 10 or 11, there are some pdf files of an old newsletter called DEVICE.  Craig Anderton has a bunch of nicely written articles throughout the different issues on working with op-amps that explain about setting gain and other issues you probably want to understand more about.  There ARE plenty of on-line resources, but these are written for folks like us.