[sdiy] Twin diode clippers

[ezion]

Hi Andrew
Your may be over thinking this.
Take a good look at the MESA schematic, without the interconnecting wire
the path trough the diodes is always blocked.
Why draw the schematic like this?
Well just a guess, but this may be a incomplete schematic or a leftover
from a other design that was modified, cause this looks very familiar.

If you replace the interconnecting wire with a diode (often a LED) the
other diodes make sure the current path is always through this
"interconnecting" diode.
There is a good reason to do this.
If the interconnecting diode (LED) has a higher forward voltage than the
others (1N4041) the transfer characteristic (voltage v.s. current) is that
of the LED.
This makes for a nice symmetric distortion curve.
Different LED types give slightly different sound, personally I like plain
old "standard red" for this.

I like to use of this distortion circuit as the buffer amplifier for diode
bridge type VCF.
In this setting the "normal" audio signal should not distort (well maybe
slightly) the self-oscillation however drives the distortion and gets a
warmer tone instead of a squeak.

Cheers Theo
Back to lurking...

Groetjes Theo

On Sun, Jun 25, 2017 at 5:00 AM, Andrew Simper <andy at cytomic.com> wrote:

> In my research into diode clipping I noticed this circuit where there
> are two diodes in each direction to soften the clipping, but there is
> an interconnect in the centre:
> http://www.parasitstudio.se/uploads/2/4/4/9/2449159/5838251_orig.png?487
>
> I did a quick LTspice simulation using this schematic to see what the
> difference is between adding this wire and having no wire and the
> plots looked identical:
> www.cytomic.com/files/circuits/diode-clipper-dual.png
>
> Does anyone know if there is some reason to add the extra wire with
> real world diodes?
>
> Cheers,
>
> Andy
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