# Distortion 250 to Gray Specs



## Jovi Bon Kenobi (Aug 24, 2019)

To build this at late 70s gray specifications I would need to change a few values, yes? Silicon clipping diodes for sure. Different pot values as well. Does anyone have info on which components to change to get it there? Thanks!


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## Robert (Aug 24, 2019)

Add 25pF cap across R2

R3    47K
R5    470K
R6    20K
R7    20K

C1    2n2
C4    22u  (positive lead in left pad)
C5    2n2
C6    10u

D1    1N4148
D2    1N4148

Gain    C500K
Volume    A10K


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## Jovi Bon Kenobi (Aug 24, 2019)

Wow, that was fast. You are amazing! Thanks!


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## Mourguitars (Oct 3, 2019)

Thanks for the Grey spec's..wrote mods on the build sheet for next order of PCB's


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## benny_profane (Oct 3, 2019)

Just saw this. I’m a bit confused about some of those values. As far as I know, the 1M feedback resistor is in all 250 variants and the 25pf feedback cap wasn’t in the circuit til the ‘82 yellow 250. Also, where did that C5 coupling cap value come from? I’ve always seen 4u7 (except in some schematics that don’t have citations). And the A10k level? I’ve always seen A100k?

EDIT: Missed the word 'add' in the original post.


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## Jovi Bon Kenobi (Oct 3, 2019)

benny_profane said:


> And the A10k level? I’ve always seen A100k?


I followed everything above but added an a100K and it sounds great.


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## mralanmorgan (Dec 18, 2022)

Robert said:


> Add 25pF cap across R2
> 
> R3    47K
> R5    470K
> ...


By across R2 do you mean just add it to both pads on the reverse side or something?


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## Barry (Dec 18, 2022)

mralanmorgan said:


> By across R2 do you mean just add it to both pads on the reverse side or something?


Yes


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## cdwillis (Dec 19, 2022)

Here's a little graph showing different versions throughout the years


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## mralanmorgan (Dec 19, 2022)

Barry said:


> Yes


Thank you. I'm having trouble finding 25pf ceramic disc's. Will 22pf or 33pf monolithic work?


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## spi (Dec 19, 2022)

mralanmorgan said:


> Thank you. I'm having trouble finding 25pf ceramic disc's. Will 22pf or 33pf monolithic work?


yes, I'd probably use the 22.


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