Adding Clipping Section to Mosfet Booster

[tristanplaysguitar]

Hi

I'm trying to build a simple overdrive pedal by adding diodes shunting to ground after the AMZ Mosfet Booster. The booster works really well, I've replaced the gain pot with a 100ohm resistor, which gives it tons of gain but no clipping of the booster itself. I'm also using a 2N7000 instead of a BS170.

This is great, but I want to add in a switchable diode clipper afterwards. The best sound I've gotten is two Ge diodes in parallel from signal to ground. But it won't clip LEDs or silicon diodes. And two Ge diodes facing opposite directions just sounds super fuzzy, not bluesy overdrivey, if you know what I mean. I feel like I'm missing something obvious. I've been putting the diodes after the decoupling capacitor (C4).
Do I need more gain? Could I put two Mosfet boosters in series to get more gain if needed?

I'll be putting in a saturation control per AMZ labs as well, and maybe a Stupidly Wonderful Tone Control. Also a master volume at the end. I might replace R6 with a trim pot if I can get the right range.

Thanks for any and all suggestions,

Tristan

Here's the schematic:
http://www.muzique.com/schem/mosfet.htm

[midwayfair]

Poke around on AMZ more ...

http://www.muzique.com/lab/sat2.htm

http://www.muzique.com/lab/zenmos.htm

I think Jack removed his article about basic clipping options ...

Anyway, you don't need more gain. Parallel diodes facing the same direction always sound very mild.

You don't say whether you've tried silicon diodes or LEDs back to back. Did you?

Pull out your multimeter and measure the forward voltage of all your diodes. Plug them in and observe how the forward voltage interacts with the amount of distortion you get. Think of other components that can change the voltage. Experiment with using them to change what the diodes do. You may surprise yourself and find something unusual and different that you like.

[Kesh]

If Ge is clipping but not Si you may well need more gain, as Si needs about twice the voltage to clip. Maybe change that 100R for a small trimmer pot.

To tame the fizz you could put a simple RC filter after the clipping, like the Proco Rat.

You could also try putting a 4k7 in series with one of the Ge diodes, like the Harmonic Percolator.

[Jdansti]

Good points by Jon and Kesh.

You can also try symmetric vs asymmetric  arrangements. For example, two of the same type in series, and a third of the same type in parallel with the other two, but reversed. You can also use two different types of diodes for asymmetric clipping. For example, an LED and a reversed Si in parallel. The sky's the limit on choices.

[Quackzed]

you might need a series resistance before the diodes. i'd put a 10k resistor before the c4 cap and place the diodes after the 10k and before the cap
like this

A--10k--C4--out
            l
          ---
         d  d
          ---
            l
          grnd
without the series resistance the diodes may not conduct ...

[axeman010]

I know this is an old post but this is exactly what I've be been thinking about doing for some time now. I'm almost ashamed to admit it but back in 2006 I ordered and built the pcb for AMZ mini booster. Since then many pedals and an amps have been built and this board has remained populated and unused.

I appreciate that its a booster circuit and there are many, many overdrive pedals out there that achieve a specific sounds but I'm just curious if any body else has added a clipping / warping section with a tone control to achieve something wonderful or even something awful to be avoided!