Mad Bean Pedals RabbitHole2020 User manual

RabbitHole2020

FX TYPE: Distortion

Based on the EHX® Big Muff™

Enclosure Size: 1590A

“Softie” compatibility: none

Overview

The 2020 version of the RabbitHole is the exact same circuit as the previous version. The PCB has

been re-designed to conform to the more recent style of 1590A layouts on mbp.

I’ve adopted the Ram’s Head as the “default” BOM for this version, as it is very popular and a good

representative of what the BM sounds like. However, there are many varieties you can build. In the

zip le for this project I have included the old spreadsheet that has different BOMs for a few versions.

Also, I highly suggest you check out the Kitrae Big Muff pages: not only for a complete history of the

effect, but for additional possible BOMS.

http://www.kitrae.net/music/big_muff_history.html

Controls

• VOL - Total Output.

• SUS - Total distortion.

• TONE - CCW - HP lter, CW - LP lter with a huge range in-between.

2.27 - Shopping List updated.

Terms of Use: You are free to use purchased RabbitHole2020 circuit boards for both DIY and small commercial operations. You may not

offer RabbitHole2020 PCBs for resale or as part of a “kit” in a commercial fashion. Peer to peer re-sale is ne, though.

Technical assistance for your build(s) is available via the madbeanpedals forum. Please go there rather than emailing me for

assistance on builds. This is because (1) I’m not always available to respond via email in a timely and continuous manner, and (2)

posting technical problems and solutions in the forum creates a record from which other members may benet.

Parts RabbitHole2020

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Values RabbitHole2020

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Traces RabbitHole2020

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B.O.M. RabbitHole2020

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Resistors Caps Diodes

R1 1M C1 100n D1 - D4 1n914

R2 33k C2 470pF D5 1N4001

R3 100K C3 100n Transistors

R4 470K C4 100n Q1 - Q4 Si

R5 100R C5 470pF Pots

R6 12k C6 100n SUS 100kB

R7 560R C7 100n TONE 100kB

R8 8K2 C8 470pF VOL 100kB

R9 100K C9 100n

R10 470K C10 3n9

R11 100R C11 10n

R12 12k C12 100n

R13 8K2 C13 100n

R14 100K C14 47uF

R15 470K C15 100n

R16 100R

R17 12k

R18 33k

R19 33k

R20 470k

R21 100K

R22 12k

R23 2K7

R24 100R

R25 4k7

Shopping List RabbitHole2020

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I’ve listed the transistors just as “Si” because there

are many BJT that will work here. If you want the

true “Rams Head” experience then I have linked two

versions of the period correct transistors used on the

next page. I’m not sure of the pinouts of the smallbear

transistors.

Value QTY Type Rating

100R 1 Carbon / Metal Film 1/4W

100R 3 Carbon / Metal Film 1/8W

560R 1 Carbon / Metal Film 1/8W

2K7 1 Carbon / Metal Film 1/8W

4k7 1 Carbon / Metal Film 1/8W

8K2 2 Carbon / Metal Film 1/8W

12k 4 Carbon / Metal Film 1/8W

33k 3 Carbon / Metal Film 1/8W

100K 4 Carbon / Metal Film 1/8W

470k 4 Carbon / Metal Film 1/8W

1M 1 Carbon / Metal Film 1/8W

470pF 3 Ceramic / MLCC 16v. Min

3n9 1 Film 16v. Min

10n 1 Film 16v. Min

100n 9 Film 16v. Min

47uF 1 Low Prole Electrolytic 16v. Min

1n914 4

1N4001 1

Si 4 NPN - medium hFE

100kB 3 PC Mount 9mm

2.27 - Updated shopping list to show (1)

100R at 1/4W and (3) 100R at 1/8W.

madbeanpedals

Parts Guide RabbitHole2020

2N5133:

http://smallbear-electronics.mybigcommerce.com/transistor-2n5133/

SE4010 (Higher gain version of the 2N5133):

http://smallbear-electronics.mybigcommerce.com/transistor-se4010-fairchild/

Low prole Electrolytic caps:

http://smallbear-electronics.mybigcommerce.com/electrolytic-radial-low-prole-16v-1-f-100-f/

9mm PC Mount pots:

http://smallbear-electronics.mybigcommerce.com/alpha-single-gang-9mm-pc-mount/

Thinline DC Jack:

http://smallbear-electronics.mybigcommerce.com/dc-power-jack-all-plastic-unswitched-2-1-mm/

Enclosed Mono:

http://smallbear-electronics.mybigcommerce.com/1-4-in-mono-enclosed-jack/

http://smallbear-electronics.mybigcommerce.com/1-4-in-mono-enclosed-switchcraft-111x/

Lumberg Mono:

http://smallbear-electronics.mybigcommerce.com/lumberg-1-4-compact-shrouded-mono-jack/

Notes RabbitHole2020

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• There are many transistors you can use in the RabbitHole. Alternatives to the 2n5088 include

BC549C, BC550, BC182L, 2n5089, and MPSA18, as well as many more. Using different

transistors can create unique variations in tone. Be careful to use the correct pin-outs, however.

Some transistors, such as the BC549C will need to be rotated 180° from the silk screen drawing

on the PCB due to its reversed pin-out. Always check the appropriate datasheet for your transistor

BEFORE soldering.

• There is a clipping mod list in the Mudbunny doc. You can certainly do any of those clipping mods

here, if you like. There’s just a lot less room if you want to get fancy with clipping switches, etc.

This is a build where I think it’s best to just keep it simple :)

Wiring Diagram RabbitHole2020

madbeanpedals

1590A Drill Guide RabbitHole2020

Note: Drill Guides are approximate and may require tweaking depending on the types of jacks, switches and pots you use.

madbeanpedals

•This template will work for either mono enclosed jacks or the “Lumberg”

style.

• It uses the “Thinline” style DC Jack.

• It also shows the 3PDT02 bypass PCB but this is not required. If you are

wiring straight to a 3PDT you can use the same LED location on the right

side or choose a different spot.

•03.19: Drill template updated (moved VOL and SUS pots slightly

outward).

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