[sdiy] diode war, steps in clipping

[Dave Krooshof]

What ledje*?

Thanks for all the answers. Especially JH's, although
it didn't really end up in this mail, it's was a clear explanation
of the opamp issues.

If I were to make a guide to make a suitable fuzz,
with your insights, it would be much like this:


Discussed here is the use of diodes in the feedback loop
of an opamp with the goal to gain a nice distortion/clipping.
Decide on your cliping style: with or without opamp saturation.
It matters here at which voltage you'll clip: respectively
close or far away from +-VCC.
Decide on how much edge you want by using a pot in series
(~500K log) it's a knob you might want to control constantly
is stead of leaving it where it is.

Low saturation:
                        Below 1.5 volt? Then LEDs are out.
                        tastes:
                        - smooth, soft distortion with a fixed maximum signal
                        level ("hard ceiling").: 4148 with 100k resistor paralel
                        - Mellow: 1N4148 as long as they do not clip fully.
                        - shottkey diodes like 1N5817...
                        these start to clip at such a low level... its possible
                        to put an inverse-parallel pair in your guitar with a
                        toggle switch... and have a passive fuzzbox.  ;^)
                        - Try a germanium diode bridge rectifier configuration
                        with the 'AC' input across the signal (or in 
the feedback
                        path) and a variable load across the 'DC' output part
                        of the bridge rectifier.

With saturation and/or higher clipping voltages:
                        tastes:
                        - Fender M-80, Danelectro style: Red leds.
                        - The bipolar red-red LED... this way its just 
one component
                        - Try the LEDs in a bridge rectifier cinfiguration...
                        - High voltage (3.6 volt clipping): White leds.
                        They look and sound different on the scope
                       - Crazy: Red leds, light up the most!
                       - Cold, clean clipping: Blue leds
                       - Green: ?
                       - IR: yet unknown

Uneven:
            Unevenly clipping sounds a bit voicelike. The human voice- 
soundwaves
            can also look softclipped on one side (if the phases are 
still correct),
            but maybe also the uneven behavior of the different leds matter.
            Low voltage:
                       germanium and silicon diodes in the feedback
                       loop of an op amp, each pointing the opposite
                       direction as the other.
            High voltage:
                       try one white going one way and two green in
                       series going the other. Substitute red, blue etc.




Bright leds, big city.
More experiences on ledcolor/diodetypes in relation to subjective
soundquality/soundcolor are very welcome.
I'll put it on my sit to share knowLEDge, OK?
This is the info you won't find in the electronics books.


DAve



* little word joke for the dutch here...

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