Help organizing ideas with new electric guitar project

[xander]

Hey guys I'm about to start a new project and am looking for some advice. I would like to build myself a two stage circuit that I can fit inside the body of my electric guitar. The first stage will be a distortion circuit, likely an op-amp or two and some diodes for clipping. The second stage will be a headphone amplifier so that I will be able to play the guitar without the need of a standalone amplifier.
I would like both circuits to have bypass functionality. My questions for the experienced are:

1. Best op-amps for this application, any audio op-amp do? noise, slew rate matter much for this frequency range/application?

2. Would 2 9V batteries provide enough juice for both circuits? 1 for +9V, other -9V. Is it okay to power them both from the same power source?

3. I want this to work with a full sized pair of koss headphones. How do I know how much gain I will need from the amplifier to drive a pair of headphones? I don't know much about this. Do I need a power amp?

There are volume and tone pots currently in the guitar. I plan on just cutting the wire to the output and routing it into this circuitry first and then to the output. I have a Dremel to cut out some of the body of the guitar to fit these electronics inside. Any help appreciated. I'm sure I will have more questions if I get any responses. Thanks!

[pzung]

for the preamp try a tl074 op amp. most people like jrd4558 but they are noisy which may be super annoying in headphones. try a stripped down tube screamer type circuit for low parts count.

for the headphone amp look into the lm386 chip. the datasheet gives better examples of uses with values than most implementations that you will find, ie:smokeyamp. also plenty of circuits at runoffgroove website but they drive the lm386 to clip, since it is your power amp, i wouldn't make it clip because it will probably sound terrible in headphones and possible damage the small earpiece drivers. not sure about that one, but just guessing.

you should be able to get the whole thing to run off one 9v battery.

the attacks might be over powering in comparison to the decays, consider putting a simple compressor on the front end and perhaps an input buffer so as not to load down your pickup.

it will most likely have too much high frequency content when you put it together because there is no guitar speaker to roll off at 5k, you will need some kind of band pass filter, a couple of resisters and a cap to ground between the distortion and the power amp.

again whatever you build i suggest looking for the lowest noise version. standard guitar equipment is noisy but the noise is over powered by tremendous volume when used live. you won't have that volume to swamp the noise in your headphones.

-zung