wierd germanium tone control?

Started by electricteeth, November 23, 2011, 08:47:27 AM

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electricteeth


I put these on the input of transistorized fuzzes to get some different tones. Could make for a sweet standalone box though.
(No battery required.) It uses germanium diodes. Can anyone tell me exactly what I am doing here? I kind of get it and it seems
like it shouldn't work but it does! Explanations?

DavenPaget

Quote from: electricteeth on November 23, 2011, 08:47:27 AM

I put these on the input of transistorized fuzzes to get some different tones. Could make for a sweet standalone box though.
(No battery required.) It uses germanium diodes. Can anyone tell me exactly what I am doing here? I kind of get it and it seems
like it shouldn't work but it does! Explanations?
I don't know what you are trying to do but it looks like you are half wave rectifying the signal when in the middle of the pot ,  :icon_eek:
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electricteeth

It goes as the first stage of a fuzz face (before the first tranny) and makes a decent range of different clipping sounds. When set to 12o'clock it is at its "cleanest". Works well enough but that doesn't stand well when I don't understand exactly why it is doing what it is doing...

DavenPaget

Quote from: electricteeth on November 23, 2011, 09:24:40 AM
It goes as the first stage of a fuzz face (before the first tranny) and makes a decent range of different clipping sounds. When set to 12o'clock it is at its "cleanest". Works well enough but that doesn't stand well when I don't understand exactly why it is doing what it is doing...
Halfwave rectification , the same way (some) AC power supplies are rectified  :icon_mrgreen:
That's not actually a tone control but can make a sick fuzz
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electricteeth

Yeah! Exactly, Much less of a tone control and more of a "shape" control (Because of rectification). Gives all sorts of weird clipping and crackling! I know that diodes are active components but does this count as a passive circuit? If so we could call it the "passive face"?

nexekho

I've got something similar to this in a little experimental pedal I made a while back.  Very synthy buzzy sound.
I made the transistor angry.

DavenPaget

Quote from: electricteeth on November 23, 2011, 09:37:27 AM
Yeah! Exactly, Much less of a tone control and more of a "shape" control (Because of rectification). Gives all sorts of weird clipping and crackling! I know that diodes are active components but does this count as a passive circuit? If so we could call it the "passive face"?
Throw it in any tone circuit and label it Shape , that should do the trick ( yea , it's a passive circuit , as long as no external power supply is required . )
Epic ideal you got there !
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Scruffie

At halfway you have coreing diodes, they're allowing signal to pass at the threshold of the diodes.

stringsthings

Quote from: electricteeth on November 23, 2011, 08:47:27 AM

I put these on the input of transistorized fuzzes to get some different tones. Could make for a sweet standalone box though.
(No battery required.) It uses germanium diodes. Can anyone tell me exactly what I am doing here? I kind of get it and it seems
like it shouldn't work but it does! Explanations?

if the input is an AC signal, then the diodes will pass either the positive part of the wave or the negative part ( as long as the signal is big enough to get the diodes to conduct ) ... with the pot, you're controlling the symmetry of the output wave ... a symmetrical wave ( pot centered ) is the cleanest sounding signal ... as you move the pot away from center in either direction, the output wave becomes asymmetrical and "less clean" ...

DavenPaget

Quote from: stringsthings on November 23, 2011, 09:59:14 AM
Quote from: electricteeth on November 23, 2011, 08:47:27 AM

I put these on the input of transistorized fuzzes to get some different tones. Could make for a sweet standalone box though.
(No battery required.) It uses germanium diodes. Can anyone tell me exactly what I am doing here? I kind of get it and it seems
like it shouldn't work but it does! Explanations?

if the input is an AC signal, then the diodes will pass either the positive part of the wave or the negative part ( as long as the signal is big enough to get the diodes to conduct ) ... with the pot, you're controlling the symmetry of the output wave ... a symmetrical wave ( pot centered ) is the cleanest sounding signal ... as you move the pot away from center in either direction, the output wave becomes asymmetrical and "less clean" ...
It's basically a variable phase halfwave rectifier , depending on how much travel is on the pot , i do lots of power supplies to know what's happening next ;)
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mrmoo1337


[/quote]
It's basically a variable phase halfwave rectifier , depending on how much travel is on the pot , i do lots of power supplies to know what's happening next ;)
[/quote]

No, theres no rectifying going on there, the output signal will be able to swing both positive or negative.  The previous posts were right, its allowing you to shape the wave by changing the resistance for the positive and negative sides of the signal independently.  But the behavior is likely to change depending on whats driving and loading it. 

DavenPaget

Quote from: mrmoo1337 on November 23, 2011, 10:38:13 AM

It's basically a variable phase halfwave rectifier , depending on how much travel is on the pot , i do lots of power supplies to know what's happening next ;)
[/quote]

No, theres no rectifying going on there, the output signal will be able to swing both positive or negative.  The previous posts were right, its allowing you to shape the wave by changing the resistance for the positive and negative sides of the signal independently.  But the behavior is likely to change depending on whats driving and loading it. 
[/quote]
Well you may disagree , but that's how i understand diodes setup that way will react to a AC source , this is clearly (to me) a variable positive or negative halfwave rectifier . If you mean fullwave then that's definitely different , because halfwave allows a either positive or negative to swing to 0 .
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joegagan

#12
this diode thing is a nice simple control. i like it.
more complicated but really fun in front of a fuzz is a dual gang wired like a dpdt bypass switch, switching between buffer/non-buffered signal. anytime it is anywhere but full cw or full ccw, there is a bit of phase cancellation going on.
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FastJunkie

I could be wrong too but I think that should just be a variable "crossover distortion" of sorts?

Mark Hammer

You're not wrong.  You're actually the prizewinner.  The circuit, as shown, will introduce clipping of the rise and fall of waveforms.  If it gets "buzzy", that is likely because the diodes will require the input signal to be above +/-220-250mv or so, in order to yield anything at the output.  And in the absenceof any boost prior to the input, only small portions of the raw guitar signal will exceed that threshold, yielding something akin to a signal with maybe 10% duty cycle, or less.