Voltage limiter for a guitar distortion circuit

A clamp. Put two diodes in antiparallel with each other, in shunt from the signal path to ground. That will limit the voltage to about .6V peak; for 1.2V peak, use series diodes.

Good Luck! Rich

P.S. Do googlies ever come back to look for answers, or do they expect them to be lying on the desk in the morning?

Diodes are as close as you are going to get. Note that this distortion is not good sounding. Most analog "distortion" pedals either are transistor based(overdrive a transistor so it clips) or based on diodes but with op amps and some filtering to smooth it out.

The reason is that semiconductor based clipping is very good... too good. The cliping is almost perfect and creates very distorted sounds(even when just a little). This creates a ton of harmonics on the signal. This is more used for metal type of distortion. Generally it is called "distortion".

Tubes, OTH, clip gradually and tend to be much more pleasing(they sorta round the edge of the sin wave rather than a sharp clip). This is generally the "overdriven" sound. Generally called "overdrive".

You have digital distortion methods now that emulate the above and can vary between both extremes. Generally it is not as good as tubes but better than silicon because silicon is easy to emulate since it is so perfect. Tubes are not perfect and are extremely complicated when you consider all the other circuitry that works together in complex manners(each tube section and the EQ and stuff all interact in a complex way that may or may not have been designed that way and hence it's sometimes hard to emulate). Good digital distortion can come close to tube's but tubes offer a feel that nothing else gives. It's probably the headroom that one gets but I'm not even sure that can explain it.

In any case, there are many circuits online for making distortion boxes. Some are very simple and some are very complex. The general idea though is always the same.

Be sure to use some series resistance ahead of the diodes, to limit current.

You can also use two LEDs instead of regular diodes. This will not only give a higher peak-to-peak (depending on diode color) but will also give razor-sharp clipping for more harmonics... if that's what you want.

The amount of gain you use ahead of the clipper will determine the point where clipping starts. You may want to use a lot of gain here to get full distortion even on fairly low levels.

You can also use an op-amp wired as a comparator, perhaps with a bit of positive feedback for hystereis so it stops in silence and doesn't trigger on background noise.

You can mix the clean and distorted signals together using a pot as a balance control. Use a 10K to 100K pot, connect one end to the clean signal and one end to the distorted signal, and use the wiper as the output.

Best regards,

Bob Masta DAQARTA v4.51 Data AcQuisition And Real-Time Analysis

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