Digitech - Bad Monkey  [schematic]

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

So, got one in and traced it.

Speaker sim out is similar to the Screamon Blues pedal
Digitech - Bad Monkey.JPG
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Post by Cups »

This is supposed to be similar (or identical) to the DOD juice box. From memory they look quite similar. I had a Juice Box and liked it a lot.

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Post by atreidesheir »

Cups wrote:This is supposed to be similar (or identical) to the DOD juice box. From memory they look quite similar. I had a Juice Box and liked it a lot.
I thought this was a poor man's bb preamp
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Post by Bernardduur »

Must say that this was a b*** to trace; I don't like SMD...... so there could be some errors...... also some caps I can't measure and did not have any signs so there are left blank. I'd guess that most of em are in the pF region..........

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Post by Dirk_Hendrik »

Bernardduur wrote: I don't like SMD......
sissy :mrgreen:
Sorry. Plain out of planes.

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Post by atreidesheir »

Is there a good method to mod smd? it might tip me more in that direction someday. Eyesight and steady hand are also a concern.
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Post by Bernardduur »

Small note:

All vref resistors around the FET's are 100k; the FET's messed up my measurement (and I see that they are marked the same on the PCB)
There is one diode missing in the PSU; it is marked SK14 and is in line with the DC power
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Post by eatyourguitar »

what kind of FET's and what kind of transistors are in this thing?

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Post by J0K3RX »

I have 2 of them that I got from pawn shops... spent $30 total for both :D I love them but they are so cheap it's hard to bring myself to build one... Maybe I will open them up and see if I can id some of the parts in question. I have 2 different versions I think? The speaker sim not so good.

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Post by Ice-9 »

eatyourguitar wrote:what kind of FET's and what kind of transistors are in this thing?
All fets are J201
All transistors are 2N3904
C1 = 120p
C10= 220p
C18 = 47p
clipping diodes = 1N4148
These are the missing values, i havent checked other values.
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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Post by Ice-9 »

ohh and the opamps are NJM4580
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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Post by IvIark »

Is Q11 the wrong way around? I thought the collector would be going to V+
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Post by Ice-9 »

IvIark wrote:Is Q11 the wrong way around? I thought the collector would be going to V+

Yes Q11 is drwan the wrong way around, it is just a standard gyrator circuit andthe collector does indeed go to +ve
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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Post by Chugs »

Are the tapers on the High and Low controls B type or W?

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Post by Ice-9 »

Chugs wrote:Are the tapers on the High and Low controls B type or W?
From memory I think they are both 100k W
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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Post by touringbubble »

Hi everyone! I'm just now getting in to building and am getting a lot from browsing the forums here. Thanks a ton for all the schematics and tips!

I had a question about the Bad Monkey schematic here. I've been looking at schematics of pedals that I'd like to try out, and this was on the list. I can tell it's a bit more complicated than a standard boost pedal, and I can appreciate that at my non-existent skill level.

If I wanted to build the main instrument circuit of the BM without the emulated output, would it be as simple as not building the circuit for the speaker output and simplifying the adapter circuit to match a standard +9v setup? Or, is that power schematic important for the proper voltage to the main circuit?

Thanks for the input!

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Post by Ice-9 »

touringbubble wrote:Hi everyone! I'm just now getting in to building and am getting a lot from browsing the forums here. Thanks a ton for all the schematics and tips!

I had a question about the Bad Monkey schematic here. I've been looking at schematics of pedals that I'd like to try out, and this was on the list. I can tell it's a bit more complicated than a standard boost pedal, and I can appreciate that at my non-existent skill level.

If I wanted to build the main instrument circuit of the BM without the emulated output, would it be as simple as not building the circuit for the speaker output and simplifying the adapter circuit to match a standard +9v setup? Or, is that power schematic important for the proper voltage to the main circuit?

Thanks for the input!
You need the power supply part of the schematic as it divides the voltages to supply the correct Vref voltages.
Yes, just leave out the speaker output part of the circuit.
If you want to uses try bypass then some other parts can be left out a s well.
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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Post by touringbubble »

Ice-9 wrote:You need the power supply part of the schematic as it divides the voltages to supply the correct Vref voltages.
Yes, just leave out the speaker output part of the circuit.
If you want to uses try bypass then some other parts can be left out a s well.
Thanks! I would like to do true bypass if it's fairly straight forward. What other parts are you referring to that could be left out?

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Post by Ice-9 »

touringbubble wrote:
Ice-9 wrote:You need the power supply part of the schematic as it divides the voltages to supply the correct Vref voltages.
Yes, just leave out the speaker output part of the circuit.
If you want to uses try bypass then some other parts can be left out a s well.
Thanks! I would like to do true bypass if it's fairly straight forward. What other parts are you referring to that could be left out?
Looking at the schematic that has been posted at the top of this thread all the parts around Q3-4 can go all the parts between C3- C4 can go including either C3 or C4 but not both, and all the parts between C28 C29 along. That's pretty much it.

Look at the schematic and see if you can follow these components and identify what they do in the circuit.

I only had a quick glance at the schematic by the way.
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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Post by Frank_NH »

touringbubble wrote:Hi everyone! I'm just now getting in to building and am getting a lot from browsing the forums here. Thanks a ton for all the schematics and tips!

I had a question about the Bad Monkey schematic here. I've been looking at schematics of pedals that I'd like to try out, and this was on the list. I can tell it's a bit more complicated than a standard boost pedal, and I can appreciate that at my non-existent skill level.

If I wanted to build the main instrument circuit of the BM without the emulated output, would it be as simple as not building the circuit for the speaker output and simplifying the adapter circuit to match a standard +9v setup? Or, is that power schematic important for the proper voltage to the main circuit?

Thanks for the input!
Here's a bufferless version of the Bad Monkey on vero. I may build this one because it is different than your standard tube screamer. I would probably try using two different diodes (e.g. 1N4148 and a 1N4001) to get some asymmetric clipping as that is my preference for op amp overdrives.

http://tagboardeffects.blogspot.com/201 ... rless.html

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