# Big Monk Pi - Gilmour Monk’s Head



## Big Monk (Apr 30, 2022)

So I’ve been down a rabbit hole the past few days looking at diodes for sale at SBE with an eye toward a specific forward voltage range.

I currently have a Muffin build that is modeled on the 1973 #3 Ram’s Head from KR’s site.

In his section on conponents and their effects on the BMP circuit, he talks about and provides measured values from some of his most prized ones. “Exceptional sounding” units to quote him directly.

I went with lower gain (actually matched around 175 hFE) Amperex A104 transistors and now I’m itching to tweak the diodes. The same unit he quoted as a stellar sounding 1973 Ram’s Head had diodes forward voltages of ~0.586-0.626.

I ran some experiments last weekend subbing in some germanium diodes with forward voltages matched at around 0.495 v. These lowered the output too much and sterilized the bigger.

I originally had 1N456 from GI leftover from the ill-fated Scrambler build and those were up near 0.8 v. I ended up with a quad of matched 1N4148 at just around 0.7 v.

I ordered about 20 glass cases silicon diodes from SBE with a forward voltage range of 0.5-0.6 v and I’m going to try those. I think those will smooth out the grrr just enough for it to be perfect.

I’m rebuilding on a new muffin board and rechristening it the Big Monk Pi, Gilmour Monk’s Head edition.

New graphics are already worked up and I’ll post them up Monday.


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## Coda (Apr 30, 2022)

I approve.


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## fig (Apr 30, 2022)

Big Monk said:


> I ended up with a quad of matched 1N4148 at just around 0.7 v.


When in doubt, throw in 4148s.


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## Feral Feline (Apr 30, 2022)

Love the name!


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## K Pedals (May 1, 2022)

Have you tried some originals ?¿

I have some I could send you…


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## Feral Feline (May 1, 2022)

Original transistors or original pedals? Sure! Send both!


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## jeffwhitfield (May 1, 2022)

fig said:


> When in doubt, throw in 4148s.


4148s…4149s…whatever it takes. 🤪


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## DAJE (May 1, 2022)

I was given a pair of weird Eastern Bloc diodes that are right in that zone, I think. Let me check...

2D212A

Both around .5 at 5mA. I have no idea what they'd be useful for but they look cool.


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## Big Monk (May 2, 2022)

So this is a flippin’ SBE shipping record:





Popped a few on the TC1:


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## Big Monk (May 2, 2022)

Measured them up tonight:





Pretty tight spread from around 645-665 for about 11 of the 14. A couple outliers > 665 and one at around 641.


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## Big Monk (May 3, 2022)

Forgot to post up the graphics:


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## jimilee (May 3, 2022)

I do like muffs


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## Big Monk (May 3, 2022)

jimilee said:


> I do like muffs



I'm holding off on my PedalPCB order until the Battery Boxes are back in stock. Then i can grab the DMD-2, another Muffin board, and a few battery boxes and get on the get.


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