MI Audio Crunchbox Mods

A forum devoted to mod, tips and suggestions for upgrading and rehousing your VERY CHEAP commercial stompbox to near boutique excellence.
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SpikeVelvet
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Post by SpikeVelvet »

Are there any mods for the MI Audio Crunchbox that will enable it to clean up better with the guitar volume knob? I built a BSIAB II and I like the way it cleans up with my guitar volume. It seems like the CB would be less of a one trick pony if there was a way to address this.

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roseblood11
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Post by roseblood11 »

Not really, I think. It`s just an opamp and diodes to ground that cut the signal. It`s possible to make simple diode clipping circuits more responsive, but it needs a few more parts. The Mad Professer Sweet Honey is a good example

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Manfred
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Post by Manfred »

Both OP-amp stages got a high gain.
Maybay reducing the gain of the second OP-ampstage could help.
Make a trial and connect a potentiometer (500kOhms, 250kOhms) in parallel to the feedback resistor (1MOhm) to find a suitable value.

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SpikeVelvet
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Post by SpikeVelvet »

Manfred,

To be clear, you are suggesting using the trimpot to find a value that achieves the desired result I am looking for, measuring the resistance and then placing that value in the circuit?

Thanks,

Kevin

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SpikeVelvet
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Post by SpikeVelvet »

roseblood11 wrote:Not really, I think. It`s just an opamp and diodes to ground that cut the signal. It`s possible to make simple diode clipping circuits more responsive, but it needs a few more parts. The Mad Professer Sweet Honey is a good example
Roseblood,

Can you elaborate on what the MP Sweet Honey is a good example of?

Thanks,

Kevin

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Manfred
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Post by Manfred »

SpikeVelvet wrote:Manfred,

To be clear, you are suggesting using the trimpot to find a value that achieves the desired result I am looking for, measuring the resistance and then placing that value in the circuit?

Thanks,

Kevin
This was the point I made with regard to the trial.
Don't forget to calculate the required resistor after reading the potentiometer value because the 1 Megohm resistor is in parallel connection,
unless the resistor is soldered out during the measurement.

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roseblood11
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Post by roseblood11 »

SpikeVelvet wrote:
roseblood11 wrote:Not really, I think. It`s just an opamp and diodes to ground that cut the signal. It`s possible to make simple diode clipping circuits more responsive, but it needs a few more parts. The Mad Professer Sweet Honey is a good example
Roseblood,

Can you elaborate on what the MP Sweet Honey is a good example of?

Thanks,

Kevin
Clean up... But it's an overdrive, with much less gain than a Crunch Box

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MoonWatcher
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Post by MoonWatcher »

roseblood11 wrote:It`s just an opamp and diodes to ground that cut the signal. It`s possible to make simple diode clipping circuits more responsive, but it needs a few more parts.
The issue with the cleanup in a design like the Crunchbox has to do with the tone circuit. You're losing a lot of treble being shunted to ground, to give the strong mid-emphasized effect.

So rip out the tone circuitry on the Crunchbox's output after the clipping diodes and second op amp stage, and put something else in there, particularly something that scoops the mids and leaves emphasis to the highs and lows (maybe not as extreme as a Big Muff, but that tone circuit would probably be a good start).

The problem becomes that it really won't end up sounding much like a Crunchbox any more.

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