Diodes with low maximum voltages?

[varialbender]

I'm looking to clip my signal with a pair of diodes. The way I understand it, diodes have a maximum voltage that they let pass, but it's usually quite a lot higher than the voltage that a guitar produces right? Are there any diodes that have a lower maximum voltage, closer to a guitar's signal, so that I can be close to squaring the wave?
Thanks

[Processaurus]

Schottky diodes (Is that how its spelled?) have a lower turn on voltage than Si and Ge diodes.  Thats whats in those passive "in guitar" distortion units (like black ice, I think one of 'ems called).  Realize the clipped output would be lower than your guitars clean output though, unless you made the clean quieter too, which might give an inferior sound to the full output of the guitars pickups.  An onboard preamp could fix that, though.

Schottky diodes are also good for protection from reverse polarity DC power in effects, because the voltage drop is smaller than a series Si diode.

[Paul Perry (Frostwave)]

Some crystal set radio designs, have a bias battery for the diode. The idea being, you can move the bias point of the diode by passing a small DC current thru it. Maybe this can be exploited for fx!!
There is a little at teh bottom of this page: http://www.techlib.com/electronics/crystal.html note, best results were with a schottky with bias.

[Processaurus]

Some crystal set radio designs, have a bias battery for the diode. The idea being, you can move the bias point of the diode by passing a small DC current thru it.

I remember someone here said that's how the Green Ringer works.  Innaresting...

[R.G.]

Are there any diodes that have a lower maximum voltage, closer to a guitar's signal, so that I can be close to squaring the wave?

The short answer is no.

There is a whole slew of exotic diodes, but there's no diode with a usable characteristic like you're asking. There are so-called backwards diode that begin conducting at substantially zero volts, but their reverse characteristic is not usable for what you want. A diode with bias may help, but we'll get to that.

Shottky (yep, correct spelling) are essentially half a silicon diode. They are a metalization on a piece of doped silicon so that only one half of the normal silicon diode junction voltage happens. Silicons conduct at about 0.5 to 0.7V, Schottky diodes conduct at about 0.25 to 0.35V.

Germanium diodes have a more sloppily defined conduction region. They have a nominal clipping voltage somewhere between 0.2 and 0.35V, but there is significant conduction all the way down to 0.1V in some of them, depending on type.

There are ways to make a "perfect" diode, with essentially zero forward voltage. These involve using an opamp and feedback to make the forward voltage insignificant. These circuits are the basis of things like Craig Anderton's Octave Fuzz and John Hollis' octave fuzz. Generally this kind of circuit is used for octaves where you want to have zero forward drop on the diodes.

The trick of passing a small current to remove some of the forward voltage is used in the Fox Tone Machine and the Green Ringer distortion pedals.

[DDD]

As far as I remember there was an article describing RF detector using "reversed" silicon NPN trannies (maybe 2n3904). Voltage drop (as per oscillograms) was about 40 (forty) millivolts.
The described schematics looks quite good.
I tried to simulate the schematic with my PC, but in vain. I think my simulation soft has too poor abilities.

[Paul Perry (Frostwave)]

I tried to simulate the schematic with my PC, but in vain. I think my simulation soft has too poor abilities.

Simulation software rarely works "outside the envelope". It is usually intended for stock standard circuits at "normal" currents and voltages.