Need help with designing a simple clipping circuit (beginner project)

[stkmtd]

Hi all, first post.

I recently attempted to put this design together:
http://www.rabbathrecordings.com/Distortion.html

I've had it sitting on the breadboard for a day, and after more debugging than I care for, I'm beginning to think it might be best to scale back my expectations and start with something simpler. The schematic is missing some documentation, so I'd rather do something simple than waste my time debugging that monster. (I've pulled out enough hair)

I would like to create a very simple clipping circuit with an op-amp and some diodes.

A number of questions immediately come to mind:
1. How does the diode clip the signal? Is a voltage limit exceeded, forcing the diode to put out a constant value beyond some threshold?
2. Is the purpose of the op-amp to "overdrive" the diode? or does it contribute to wave clipping in some way?
3. What sort of external components are needed to get the op-amp working properly? I know many semiconductor products need caps to smooth out the power supply.

Here's what I'm NOT looking for:
- Pages of winded suggestions about how I should insert {STRANGE, HARD TO FIND COMPONENT} due to {DUBIOUS REASON}
- A pedal that sounds like absolute heaven
- Any kind of controls beyond drive amount, and output volume

I am open to suggestions, but the aim of this project is to get a better grasp on the fundamentals of distortion. If filtering noise, and tone controls are an interest in the future, I'll pursue them when I can get the basic waveshaping done first.

Any resources and advice are greatly appreciated, and I'd like to share the results of this project when I finish. With a quick glance through the forum, it seems most beginners are a little more ambitious than I am. I'd be happy to just chop the tops off some sine waves. I'm sure I'm not alone in this.

For reference, the op-amp chips I have are dual op-amps (MC4558C, datasheet: http://www.datasheetcatalog.org/datasheet/motorola/MC4558CP1.pdf)
Addendum: The diodes I have are 1N914

[aron]

Take a look at this:

http://www.diystompboxes.com/smfforum/index.php?board=33.0