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RabbitHole2020

FX TYPE: Distortion

Based on the EHX® Big Muff™

Enclosure Size: 1590A
“Softie” compatibility: none

© 

2020 

madbeanpedals

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 file 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 filter, CW - LP filter 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 fine, 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 benefit.

Summary of Contents for RabbitHole2020

Page 1: ...es 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 filter CW LP filter 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...

Page 2: ...Parts RabbitHole2020 madbeanpedals ...

Page 3: ...Values RabbitHole2020 madbeanpedals ...

Page 4: ...Traces RabbitHole2020 madbeanpedals ...

Page 5: ...tors 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 ...

Page 6: ...l 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 L...

Page 7: ...trolytic radial low profile 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 switchc...

Page 8: ...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 cl...

Page 9: ...Wiring Diagram RabbitHole2020 madbeanpedals ...

Page 10: ...dals 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 ...

Page 11: ...Voltages RabbitHole2020 madbeanpedals 9 42vDC One Spot Current Draw 2mA Q1 Si Q3 Si C 4 12 C 4 12 B 0 64 B 0 64 E 42mV E 42mV Q2 Si Q4 Si C 4 12 C 4 96 B 0 64 B 1 55 E 42mV E 0 96 ...

Page 12: ...Schematic RabbitHole2020 madbeanpedals ...

Page 13: ...had only one clipping section The input section has been replaced with a BS170 for a different flavor The tone section has been dialed for a flatter response when the knob is set to the middle position It is also tweaked for less low end I pretty much made it up as I was putting it together and I think it sounds very cool Not quite a Muff but not not a Muff All four transistors are the opposite pi...

Page 14: ...nsistors R4 1M C4 100n Q1 BS170 R5 220R C5 470pF Q2 Q4 BC550B R6 4k7 C6 47n Pots R7 1k C7 47n SUS 100kB R8 10k C8 470pF TONE 100kB R9 100k C9 47n VOL 100kB R10 470k C10 10n R11 220R C11 10n R12 12k C12 100n R13 10k C13 100n R14 100k C14 47uF R15 470k C15 100n R16 470R R17 12k R18 15k R19 22k R20 470k R21 100k R22 12k R23 2k7 R24 100R R25 4k7 ...

Page 15: ...8W 4k7 2 Carbon Metal Film 1 8W 10k 3 Carbon Metal Film 1 8W 12k 3 Carbon Metal Film 1 8W 15k 1 Carbon Metal Film 1 8W 22k 1 Carbon Metal Film 1 8W 100k 3 Carbon Metal Film 1 8W 470k 3 Carbon Metal Film 1 8W 1M 3 Carbon Metal Film 1 8W 150pF 1 Ceramic MLCC 16v min 470pF 2 Ceramic MLCC 16v min 10n 3 Film 16v min 47n 3 Film 16v min 100n 5 Film 16v min 47uF 1 Electrolytic 16v min 1n914 4 IN4001 1 BS1...

Page 16: ...ou ll notice D5 is missing It s because I put the damn thing in the wrong way Took the pic before replacing it I used 100kA pot for the Vol This is more of a personal preference for me All Muffs have plenty enough output that there s no reason to use a linear taper instead of audio ...

Page 17: ...Bonus Section RabbitHole2020 madbeanpedals ...

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