Quagmire02
New member
and what do they do?
A
acorec
Banned
Quagmire02 said:
Clipping diodes are used for limiting a voltage signal. If a voltage goes above the fixed diode threshold, the diode starts to conduct the "extra" voltage and shunt it to ground. This is one application, they are also used for eliminating ESD noise at a circuit's input.
Quagmire02
New member
Do they limit volume at all?
A
acorec
Banned
Quagmire02 said:
Yes, if they were used in the bias cuircuits for the tubes. They would limit the total gain of the tube output.
G
guitarist
New member
They're also used in pedals, solid state and some modern tube amps to simulate an overdriven sound (or to get more distortion without adding more tubes).
bongolation
New member
Note that there is much imaginary and some possibly real tonal difference in those circuits depending on the specific diode. Much of the mojo attributed to the original Tubescreamers was invested in the now-long-extinct Panasonic clipping diodes.guitarist said:
moogyboy
New member
A few notes...
The way a diode works is that it acts as a kind of one-way valve. It'll let through the "positive" part of a waveform, but not the "negative". In a distortion box, the result of this is that the peaks of your guitar's waveform are chopped off at a certain point (kind of like a square wave, but retaining the characteristics of the original signal), which your ears hear as distortion. At least I think that's how it works. I'm a little hazy on why a diode pair wouldn't simply cut out both the positive and negative parts of the waveform completely, creating silence, but then I'm not really an electronics boffin.
From what I've read on the DIY stompbox websites, there are two common clipping diode implementations: 1) two diodes in parallel in the feedback loop surrounding an op-amp (I believe the MXR Distortion+, Tube Screamer, ProCo Rat etc. are like this), and 2) two diodes in parallel between the output line and ground (several old pseudo-"fuzz" distortion boxes like the Gretsch Contro-Fuzz).
The diodes are usually in pairs, and of opposite polarity, but apparently they can be unevenly matched to provide asymmetrical clipping, ie two "positive" and one "negative". Also, different types of diodes produce different sounds; I've heard that LEDs create a tube-like crunch.
Hope this helps somewhat.
cheers
Billy S.
The way a diode works is that it acts as a kind of one-way valve. It'll let through the "positive" part of a waveform, but not the "negative". In a distortion box, the result of this is that the peaks of your guitar's waveform are chopped off at a certain point (kind of like a square wave, but retaining the characteristics of the original signal), which your ears hear as distortion. At least I think that's how it works. I'm a little hazy on why a diode pair wouldn't simply cut out both the positive and negative parts of the waveform completely, creating silence, but then I'm not really an electronics boffin.
From what I've read on the DIY stompbox websites, there are two common clipping diode implementations: 1) two diodes in parallel in the feedback loop surrounding an op-amp (I believe the MXR Distortion+, Tube Screamer, ProCo Rat etc. are like this), and 2) two diodes in parallel between the output line and ground (several old pseudo-"fuzz" distortion boxes like the Gretsch Contro-Fuzz).
The diodes are usually in pairs, and of opposite polarity, but apparently they can be unevenly matched to provide asymmetrical clipping, ie two "positive" and one "negative". Also, different types of diodes produce different sounds; I've heard that LEDs create a tube-like crunch.
Hope this helps somewhat.
cheers
Billy S.
