Understanding how things work?

[wormfooduk]

Hi i've built and moded quite a few pedals now and am starting to learn how to make my own designs. Can some one read though this and give me some pointers if im getting anything wrong.

1. As far as I can tell there is 2 main ways of getting overdrive/distortion either you use a clipping stage with diodes or another (second) gain stage using one opamp or transistor to overdrive another?

2. Silicon gives hard clipping germanium gives soft clipping, leds give hard ish clipping with a more open sound and are quite loud?

3. 9v is only used because of batteries and more voltage gives you more headroom?

4. Pull down resisters are a good idea to stop popping by draining caps to ground when in bypass?

5. A boost pedal could be made into an overdrive by adding a clipping or 2nd stage and an pot at the end to control the output volume?

If anyone has a link to a guide to how drive pedals work (fet based ones would be great) that would help me allot.

Thanks Pete

[R.G.]

1. As far as I can tell there is 2 main ways of getting overdrive/distortion either you use a clipping stage with diodes or another (second) gain stage using one opamp or transistor to overdrive another?

While those are two ways of getting distortion, the number of ways to get distortion are both infinite and singular at the same time. The singular thing is that any time the output of a circuit is not exactly like the input excepting only for the size, it's been distorted. Exactly how it's distorted and how much are the infinite ways.

As a practical matter, guitar effects use clipping diodes and overdriven stages as the primary ways, because these two are easiest within the constrictures of the other practicalities of the stompbox technologies.

2. Silicon gives hard clipping germanium gives soft clipping, leds give hard ish clipping with a more open sound and are quite loud?

That's the conventional wisdom, but it's a vast oversimplification. First, read http://www.geofex.com for the Guitar Effects FAQ. It's now over a decade old, and is getting long in the tooth, but has some good understanding for you. Second, understand that hard versus soft clipping is a matter of perspective; what matters is how much of the signal waveform is "compressed" into the transition between not-very-distorted and fully-limited by the clipping mechanism. If the signal simply flat-tops (or bottoms) instantly, the clipping is harsh. If it's a softer transition, the clipping is less harsh. The circuit around any clipping devices, whatever they are, matters more than the devices themselves. Baldly stating otherwise is akin to mistakes made in Kipling's Blind Men and the Elephant.

3. 9v is only used because of batteries and more voltage gives you more headroom?

A.Yes.
B. Maybe. It depends on what you mean by headroom, and whether it matters. More supply voltage gives the *capability* to have more headroom in the sense that it's possible to have bigger signals. Whether that is practical or realized depends on the circuit.

4. Pull down resisters are a good idea to stop popping by draining caps to ground when in bypass?

Yes.

5. A boost pedal could be made into an overdrive by adding a clipping or 2nd stage and an pot at the end to control the output volume?

Maybe. Depends on what you mean by "boost", "overdrive", and also "distortion", "fuzz" and all the other words overused to death in the pedal biz. All "overdrive" means is that something, somewhere is pushed by a signal too big for it to respond without distortion (see above). A booster makes signals bigger. This may or may not overdrive the following stages. If you arrange either the boost to be big enough to overdrive something, anything, you have made an overdrive.

If anyone has a link to a guide to how drive pedals work (fet based ones would be great) that would help me allot.

Read http://www.geofex.com. All of it.

[wormfooduk]

  Thanks very much for spending your time responding to my post. I will start reading the GEO pages looks like theres alot of good info there. I really want to know about how Gain/clipping stages are setup and how different transister interact to make overdrive/distortion. But i will read the GEO site and check back if i have any questions. thanks again