MXR - Badass Modified Overdrive  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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itzalak2
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Post by itzalak2 »

Has someone the schematic of this layout?

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Thanks

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POTL
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Post by POTL »

Hello everybody
I have problems with adjusting 100 hertz
Either continuous oscillation (background which reacts to a pen)
Either pen works, but the minimum value is almost no sound, 90 percent enhanced benefits, and higher oscillation begins

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POTL
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Post by POTL »

I used 3 different potentiometer
100 50 20 kilohms

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Ice-9
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Post by Ice-9 »

POTL wrote:Hello everybody
I have problems with adjusting 100 hertz
Either continuous oscillation (background which reacts to a pen)
Either pen works, but the minimum value is almost no sound, 90 percent enhanced benefits, and higher oscillation begins
did you make your own layout from the correct schematic or have you uesed the vero layout form the poster above , which i have not checked at all.
It's fairly straight forward, if you want to start it , press start. You can work out the rest of the controls for yourself !

No silicon heaven ? preposterous ! Where would all the calculators go ?

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POTL
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Post by POTL »

I am using a development board
Image
and a circuit which is represented in this topic

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TheGunn
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Post by TheGunn »

I've encountered problem with oscillations too. After placing buffer in front of it oscillations are gone (even ts9 buffer was ok). Also anybody could explain what is the role of diodes at input and output?

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Ichabod_Crane
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Post by Ichabod_Crane »

Hello, I can't answer you about the diodes you mentioned (present in the schematic, but not in the layout).
But, about the oscillation I can give you some advice, you can see if it work in your case.

1. In the input wire stripe, cut the track at the left of the 10k resistor.
2. Move the 47nF, the one between the 10k and the B of the transistor, closer at the transistor.
3. And cut the track to the left the upper side of the 47nF (after you moved, under the 9v track jumper).

This makes the input track more isolated and less exposed to others signal tracks. I don't know if it will solve the issue, but you could try it.
In theory, you can do it for every stripe not integrally used.

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TheGunn
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Post by TheGunn »

I followed your instructions and oscillations decreased but they are still present when gain is maxed and tone control is past 50% of way. Also oscillations are gone even when I put Bluesbreaker before with it's 50k output impedance.

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Ichabod_Crane
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Post by Ichabod_Crane »

I'm not so confident, but... you can try to cut the track between the 47nF and the 10k, the stripes of the pin 1 of the IC. But this is the max we can do with this trick, I guess, I'm sorry.

Are the wires not too much long? And did you try to use shielded cable fro input and output wires?

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TheGunn
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Post by TheGunn »

I cut tracks in every possible place where it could be done and now oscillations are present only when tone control is set higher than 75%. All other controls are maxed. With bump switch engaged oscillations change pitch. My wires are all about 10cm (4 inches) long from so input is about 20 cm (from jack to switch and from switch to board added together) and aren't shielded. I know it's kinda long but I didn't think it can be so problematic if pedal has integrated input buffer. Maybe it's just poor input buffer design? Anyway I will try adding shielded wire in next few days.

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Post by TheGunn »

Shielded wire made it even worse.

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Ichabod_Crane
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Post by Ichabod_Crane »

Probably you did it, but check your board again in case of some mistake.

Maybe with some pictures front and back, we can help you.

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