Build Your Own Clone Message Board

Hey all. Just starting out the Orange Distortion, and looking at the options for modding the clipping. There are the 4 diode pads on the pcb, and I understand the stock option (2 1n4148s, jumpers in the other pads). The build docs mention other options, like the "Marshall mod" (2 symmetrical leds, which were included in the kit), but also mentions diode "stacking".

I like the idea of the marshall mod, so would that just be to put the leds where the 1n4148s go (with cathodes laid out the same way), and jumper the same way as in the stock layout?

Is there an option/advantage to using all four placements (is this what the directions mean by "stacking" the clipping?)

The kit included 2 extra 1n4001. Are these meant as a clipping option as well?

I think i will also do the muff mod with the additional diodes off to the side.

In short, can someone tell what my other options are AND how to lay them out?

Let me start with a few words about how audio signal clipping works (though you may already know this): When the amplitude of the audio signal exceeds the forward voltage threshold of the clipping diode that it's passing through, the signal above that threshold gets "clipped", that is it's shunted out of the audio signal path. Because audio signals are AC in nature and are a sinusoidal waveform, they have both a positive and a negative side. This is why clipping diodes are paired in opposite polarities, to be able to clip each of the sides of the waveform. The lower the forward voltage threshold (FVT) of the diode, the more of the audio signal that will be clipped off. Silicon diodes like the 1N4148 have a FVT of about 0.6V, while a red LED is much higher at about 1.6 - 2.0V. So using a pair of LED's for clipping will give a louder, less distorted and less compressed output than a pair of silicon diodes, because less signal is clipped off by the higher FVT. Germanium diodes like the 1N34A or 1N60 have an even lower FVT than silicon diodes, down around 0.2 - 0.3V.

When the same type & number of diodes are used to clip both sides of the waveform, that's called symmetric clipping. But asymmetric clipping is quite commonly used as well, and gives a somewhat different character to the output. Examples of asymmetric clipping diode combinations would be a silicon diode paired with an LED, or a single silicon diode on one side paired with two silicons in series on the other (this would also be an example of "stacking"). BTW, the FVT's of two diodes in series is additive.

So the bottom line is that you have a LOT of choices with how you set up your Orange Distortion build. If you want to be able to "audition" some different diode combos, I would suggest installing single inline (SIL) sockets in the clipping diode eyelets of the PCB. These will let you try different combinations without needing to solder and desolder each diode change. The thicker leads of the 1N4001 diodes won't fit in the sockets, but they sound virtually identical to the 1N4148's, to my ear.

There are a number of other modifications that can be made to the Orange Distortion circuit as described on pages 8 & 9 of the instructions. The SIL sockets can be used to experiment with those, as well, if you so choose.

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