been a while, thought i'd drop something "new" on ya'll

[pinkjimiphoton]

nice! i gotta do a build tonite for someone, and gig tomorrow, hoping to build up something for this weekend. if i had a half a brain, i'd do it on my breadboard, but the contacts are so worn out its a mega pia!

[amz-fx]

On the (incorrect?) schematics there's no feedback resistor on the second amp but in the actual pedals there was a 470k resistor.

Thanks! I'm not sure who drew that old schematic but it has been circulated for many years, and from your pix it looks to have more errors than I thought. Or like many old EHX pedals, the values of the components may have differed over the years depending on what resistors and capacitors could be purchased cheaply on the local market (long before China sold any parts or products to the USA).

Best regards, Jack

[amz-fx]

I took a few minutes to draw up the schematic from your pictures. The board is so nasty that I'm not sure this is exactly right, but it will work.



regards, Jack

[j_flanders]

Thanks Jack. It looks correct to me.
As far as I know that is the first correct schematic for the opamp Muff Fuzz on the entire world wide web.
Edit: diodes are 1N4148:


There was another version that had 680k resistors for the bias voltage.
But I can't tell for sure if the rest of the circuit was identical. The layout is different as are the clipping diodes.
I think there's only one picture in the photo albums below with the component side and even that one shows very little.


Here are some albums for that 680k version:
https://postimg.cc/gallery/2r4pdgf2i/
https://postimg.cc/gallery/iz9485sa/


Here are some more pictures for the 1M bias resistors version:
https://postimg.cc/gallery/2351lzv4a/

These are some unsorted pictures:
https://postimg.cc/gallery/2vcayxop6/

[Mark Hammer]

I took a few minutes to draw up the schematic from your pictures. The board is so nasty that I'm not sure this is exactly right, but it will work.



regards, Jack

If a person wishes to employ the Bluesbreaker/KOT trick, consider making the 470k feedback resistor in the first stage 390k, and inserting a 100k pot.  The wiper goes to the output of stage 1, the "left" lug of the pot (looking at it from the front, with the lugs pointing downwards; i.e., the lug one would normally use as the ground connection on a volume control) goes to the free end of the 390k, and the other outside lug goes to the 10k input resistor of the second stage.

What we end up with is a circuit that will range from a gain of 16.7x to a gain of 230x.  Note that the Tube Screamer provides a max gain of 213x, so this modded version will go from a boost that has a hint of dirt when you dig in, to a nicely compressed sustaining tone.  The added 100pf feedback cap should yield a pleasing warm tone that still has some bite.  Make it 150pf if there's too much bite.  Alternatively, consider sticking a 100pf feedback cap in the first stage as well.

With the mods, it should make a nice adjustable utility drive.  Thanks for the redraw, Jack.  Much appreciated.

[petey twofinger]

whats a jellybean ?

[pinkjimiphoton]

a chip, petey

[willienillie]

Is it just me, an optical illusion, or are those clipping diodes pointing the same direction?