The hard clipping diodes could go right after the 22uF cap after the input stage, but would benefit alot from Another stage after, to bring the level back up, as the clipping will lower the signal volume, so i would add a gain pot Before the diodes, and Another stage after.

Soft clipping, i have only seen done with op-amps. cant really say how well they would work or how to be done with a transistor.

Edit:

Found this at GeneralGuitarGadgets, uses both types of clipping.

I think you would prefer soft clipping then. (diodes in the feedback loop of a gain stage)

You can also use a boost pedal in front, which usually basically works just like adding another gain stage in front of the others. The result depends on how the circuit works. A nicer distorsion requires some tone shaping in my opinion, filtering out some frequences that would make the sound "muddy" for example. It's not easy making a heavy distorsion, although there are some diy versions out there that sounds great. (Madbean upper decker, j0k3rx's black forest) etc.

For less distorsion, but great sound. Take a look at maxon od808 or any of the tube screamers. Might take some work integrating into your preamp, but good way to learn i suppose.

To increase distortion you could either add more gain stages, amplifying past the headroom voltage avaliable to the transistor, it will then cut the peaks of the waveform creating distorsion, or you could use clipping diodes. There are several ways of doing this, but the simplest form is just 2 facing the opposite direction in parallel shunted to ground. You might wanna add another gain stage after them to keep the signal at the desired level for he power amplifier.

I'm working at a heavy distortion preamp design, which i will upload once it is done, it uses both soft clipping and hard clipping through diodes.

Using the clipping diodes on the output makes the amount of clipping volume dependant, you might get a better result using a separate gain for that and a gain stage after that amplifies the 0.7 or so volt you got after clipping to the wanted max level. Otherwise, once they start clipping the volume knob wont increase the volume, just add distorsion.

The diodes looks like polarity protection or something like that, cant say for sure. Distortion should happen in the preamp, while the power amp should be as clean as possible.

Havent heard it myself, but if you got the power supply and a heatsink already, its really cheap to build the single supply circuit jm suggested from the datasheet. 7 caps, 4 resistors, the ic and 2 diodes.

In my opinion i think you will benefit more from overdriving the preamp when it comes to solid state circuits.

As jm says, you should probably abandon that amp for a better suggestion, i just wanted to make the supply configuration clear. As a dual supply with center tap referenced ground is not the same as a single supply.

Edit: you can still split a single supply, but you will need to add a virtual ground, and remove the dc offset created that way. It wont just replace the psu out of the box.

That might explain some of the problems with the first Circuit aswell. There will be no headroom avaliable at the negative side of the signal which will distort bad.

Ok, just checking to make sure you have both positive and negative supply. (+/- 12 or 24 v), as if you used a single supply you would need to offset the voltage to 12v if using a single 24 supply, and also the "ground" would need an offset to the virtual ground at 12v.  The red circuit regardless how bad, says +/- 24 v. 48v transformer with center tap.

Yeah, i have both 4053's, a load of low current relays, and ldr's that i'm experimenting with. Im going for one clean, and two high gain channels.

There will also be a built-in maxon od808-ish boost circuit which can be switched in before the high gain channels to boost signal, and a delay instead of the classic reverb.

Now, theres quite a few components, but i really build this to suit the way i play. The footswitch can be used in two ways, either as a plain channel switch, but also programmable to activate "banks", ie. Button 1 = channel 2, button 2 = channel 3, boost and delay.

Yeah. They should clip at very much higher level than the 4148's

The zeners are clipping the signal. The orientation of them is setup that way to clip both the positive and negative part of the waveform.

Just a Little curious about one thing, just to make sure. when you say your supply is 24v, does that mean single or 2x12 with a center tap referenced to ground?

Alright. thanks again guys.  :dbtu: