Chuck D. Bones
Circuit Wizard
"You can't have too many Dirt Pedals."
This one is loosely based on the Krank Distortus Maximus. The DM is basically an LPB driving an LM386 with a Marshall TMB stack at the end. The LM386 is largely responsible for the sound. The DM is a great sounding pedal in stock form, but I saw an opportunity for some improvements. The 1st stage is now a Sziklai pair, using a JFET & a Si PNP. It has a higher input impedance and more gain. I changed the way the GAIN control is implemented for easier adjustment and lower noise. I added a bass cut switch (FAT) up front and a treble cut switch (BRITE) between stages. I stuck a 3-way gain switch (CRUSH) on the LM386. Lastly, I rescaled the impedances in the TMB stack to take full advantage of the LM386's drive capabilities and switched it to a Fender-style tone stack to increase the available Bass boost. The higher input impedance and lower output impedance enables this pedal to stack well with other pedals.
I'm digging the sound. With CRUSH at max and the FAT and BRITE switches off, it sounds like a DM. Chords hold together pretty well. Turn the FAT switch on and it's a BEAST. Either way, there's plenty of sustain and it's great for feedback. Has a great chunk sound when I dig in with the pick. Lots of bass available at low to moderate GAIN settings. Bumping up C3 and C8 will extend the bass response at higher GAIN settings. There is a provision for driving a back-to-back pair of red LEDs for the magic-eye effect, that's the red wire at the bottom that goes nowhere. Tried 'em out on the breadboard, but have not yet installed them on the boxed-up unit.
As a nod to Krank, I retained a Roman-style name, but changed it to one of the characters in Monty Python's Life of Brian: Biggus Dickus.
Controls are (L-R):
Top row: Volume, Crush, Gain
Middle Row: Brite, Fat
Bottom Row: Treble, Mid, Bass
It's not nearly as pretty inside as one of HamishR's boxes. There's some clear heat-shrink on the power jack terminals and LED leads.
Here's the fit check, before wiring it all up. Those three switches were a pretty tight squeeze.
Here's the board with enough wires for an aliveness check. I managed to not muck anything up this time and it worked right out of the chute. The final verision has a JRC NJM386 in place of the TI LM386.
This one is loosely based on the Krank Distortus Maximus. The DM is basically an LPB driving an LM386 with a Marshall TMB stack at the end. The LM386 is largely responsible for the sound. The DM is a great sounding pedal in stock form, but I saw an opportunity for some improvements. The 1st stage is now a Sziklai pair, using a JFET & a Si PNP. It has a higher input impedance and more gain. I changed the way the GAIN control is implemented for easier adjustment and lower noise. I added a bass cut switch (FAT) up front and a treble cut switch (BRITE) between stages. I stuck a 3-way gain switch (CRUSH) on the LM386. Lastly, I rescaled the impedances in the TMB stack to take full advantage of the LM386's drive capabilities and switched it to a Fender-style tone stack to increase the available Bass boost. The higher input impedance and lower output impedance enables this pedal to stack well with other pedals.
I'm digging the sound. With CRUSH at max and the FAT and BRITE switches off, it sounds like a DM. Chords hold together pretty well. Turn the FAT switch on and it's a BEAST. Either way, there's plenty of sustain and it's great for feedback. Has a great chunk sound when I dig in with the pick. Lots of bass available at low to moderate GAIN settings. Bumping up C3 and C8 will extend the bass response at higher GAIN settings. There is a provision for driving a back-to-back pair of red LEDs for the magic-eye effect, that's the red wire at the bottom that goes nowhere. Tried 'em out on the breadboard, but have not yet installed them on the boxed-up unit.
As a nod to Krank, I retained a Roman-style name, but changed it to one of the characters in Monty Python's Life of Brian: Biggus Dickus.
Controls are (L-R):
Top row: Volume, Crush, Gain
Middle Row: Brite, Fat
Bottom Row: Treble, Mid, Bass
It's not nearly as pretty inside as one of HamishR's boxes. There's some clear heat-shrink on the power jack terminals and LED leads.
Here's the fit check, before wiring it all up. Those three switches were a pretty tight squeeze.
Here's the board with enough wires for an aliveness check. I managed to not muck anything up this time and it worked right out of the chute. The final verision has a JRC NJM386 in place of the TI LM386.
