Distortion 250 to Gray Specs

[Jovi Bon Kenobi]

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!

 

[Robert]

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

 

[Jovi Bon Kenobi]

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

 

[Mourguitars]

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

 

[benny_profane]

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.

 

[Jovi Bon Kenobi]

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

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

 

[mralanmorgan]

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

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

 

[Barry]

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

Yes

 

[cdwillis]

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

 

[mralanmorgan]

Yes

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

 

[spi]

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

yes, I'd probably use the 22.