New Overdrive project for ya: The Microdrive.

[scottso]

 

I would love someone to enlighten me on what is the difference between having one clipper diode or 2 in series in such circuits. I feel that all that adding another diode of the same type in series will do is to increase the output levels. Which could have been done with the level control anyway. Now maybe if the second diode was of a different type or had a resistor in series or parallel to it ...................

 

 

Quoting from this site (click on the mods section):

 

http://www.geofex.com/Article_Folders/TStech/tsxfram.htm

 

 

Sweeter distortion - the stock units use a pair of silicon signal diodes, which look identical to the 1N914/1N4148 devices. If you change one of these diodes, chances are that the resulting pair will not clip at the same voltage for positive and negative signals, giving you asymetrical clipping, and the resulting even order distortion. If you pick something close, like maybe a silicon power diode like the 1N400x series for the second diode, the resulting second harmonic will be very subtle, not audible as an octave effect at all, just a "sweeter" or more liquid tone. You can try a number of things like putting one germanium (1N34A from Radio Shack works) diode in series with one of the silicons to add a bit more threshold voltage to one side. A more radical treatment would replace one of the silicons with three germaniums; even more radical would replace one of the silicons with TWO silicons. These last will start to make an octave effect just barely audible at some notes on the guitar neck.

 

[Web Surf]

The geofex site refers to having only two clipping diodes and changing one of them to a different type. Thats easy to understand.

 

This circuit here is about two identical diodes, or 4 identical diodes

 

Please explain the reason of switching in 2 more of the same type of diode.

[scottso]

 

The geofex site refers to having only two clipping diodes and changing one of them to a different type. Thats easy to understand. This circuit here is about two identical diodes, or 4 identical diodes Please explain the reason of switching in 2 more of the same type of diode.

 

 

Its explained pretty clearly here:

 

 

You can try a number of things like putting one germanium (1N34A from Radio Shack works) diode in series with one of the silicons to add a bit more threshold voltage to one side. A more radical treatment would replace one of the silicons with three germaniums; even more radical would replace one of the silicons with TWO silicons. These last will start to make an octave effect just barely audible at some notes on the guitar neck.

 

 

Changing the amount of diodes in series changes the threshold voltage which will change the sound of the distortion. It will also make the distortion asymmetrical if you use different quantities or types of diodes on each side which tends to subjectively sound better when used before a tube pre-amp. Solid state symmetrical sounds better to some people. But the key word here is subjective.

 

The schematic posted on this thread pretty much says as much by telling you to swap out different diodes for a range of sounds. The schematic shows 4 identical but if you read the text next to the schematic he says to switch them up for a range of sounds to taste. Considering the vast amount of distortion circuits available on the Net that use differing amount of diodes for their distortion, I'm a little amazed you question whether they have an effect. Have you built a DIY distortion circuit before?

 

This site gives a bunch of different circuit designs by "big names" that use differing amount of diodes for their characteristic sound:

 

http://users.chariot.net.au/~gmarts/ampovdrv.htm

 

If you want more technical information you should probably get a basic electronics book and look up the chapter on diodes or Google for more info. It's easy enough to build out a basic distortion circuit (or this one) on a breadboard and plug in differing amounts of diodes and you will hear the changes to the effect as you swap them in and out.

[konsole]

Thanks scottso, good explanation. It's basically all to do with threshold voltages and clipping levels. Singular diodes will clip the waveform way more than double diodes - resulting in a greater deformation of the original waveform. If you build up a few distortion circuits and experiment you can easily see that different diode types/numbers have a great impact on the overall tone.