NYC Big Muff Pi Re-issue Modifications (3003-A Circuit)

[Big Monk]

So I was able to grab a sort of "bombed out" NYC BMP Re-issue off reverb a few months ago. I've always steered clear of the Big muff but I have been listening to a lot of clips for the EQD Hoof and Blackout Musket and thought i'd take a shot:



As you can see, at least aesthetically, it's the perfect candidate for mods. It actually turned out to be a good "bedroom blaster" (I have been having a ball playing at low volume through my Marshall MS-2 mini amp) pedal when combined with my Small Bear GE "Flathat" Ge Mid Booster.

So, of course I couldn't leave well enough alone. When playing at normal volumes, it was very woofy without the treble/mid booster. Looking through the kitrae site and doing general research, I checked through my parts bin. I wanted to change out the DC jack for a barrel type, I had some extra switchcraft black box style jacks (the jack were a bit dodgy), some NOS Amperex Ge diodes from Small Bear, and enough 0.1 film caps to replace at least the input cap and the coupling caps in the clipping stages. Also, I drilled an extra hole on the face to mount the treble/mid boost into the circuit.

So last night I was able to get the diodes in, all three caps, replace the signal jacks and the DC jack. I did lift a few traces from late night, overzealous soldering (I have put off a new tip for my Weller and last night was the last stand) when putting the coupling cap replacements in but was able to just tie them in at an upstream trace.

My first thoughts? The gain was significantly reduced. This was bedroom level so I have not had a chance crank it up, but a lot of the low volume "Big Muffy-ness" is gone. I'll mourn the loss of my bedroom blaster for sure! When boosted the tone seemed very nice but less wild. I definitely ruined my late night, low volume riff monster but think the cranked up tone will be much better.

More to report later.

[j_flanders]

V9 is the perfect candidate for a conversion to Russian (V8) specs. Not much that needs to be replaced but it'll sound very differently.
You'll loose the woofy bass, which, in the V9 and V10 versions, is way over the top anyway.
V10 even adds more gain on top of that woofy bass. It becomes a muddy mess imo.
V8 FTW!
Here's an overview of the differences between V8(black russian) V9(NY RI) and V10 (Little Big Muff XO):




I modded my V9 and V10(smd...) to V8 specs and they sound pretty much identical to my EHX black Russians.
I didn't bother replacing components if the difference was too small (like 470k vs 510k or 20k vs 22k).

PS: don't go by the pcb component numbering found on KitRaes site. They are often incorrect.
IIRC he has some of those emitter resistors r10, r16, r20, r21 incorrectly numbered or reversed for V9.

[Big Monk]

PS: don't go by the pcb component numbering found on KitRaes site. They are often incorrect.
IIRC he has some of those emitter resistors r10, r16, r20, r21 incorrectly numbered or reversed for V9.

Thanks for this. I made some edits which i think brings it in line with the circuit I have (3003-A):

[j_flanders]

Thanks for this. I made some edits which i think brings it in line with the circuit I have (3003-A):

Yes, that appears to be correct as far as I can remember.
3003-A is what I have as well.
I think C6 and C7 are on the 'wrong' side of the diodes in the schematic.
C6 is connected R18 to and C7 is connected to R11.
Not that it matters circuit-wise...

Somewhere on his site he does explain why numbers Q1,Q2,Q3,Q4 in reverse order.

[Big Monk]

Thanks for this. I made some edits which i think brings it in line with the circuit I have (3003-A):

Yes, that appears to be correct as far as I can remember.
3003-A is what I have as well.
I think C6 and C7 are on the 'wrong' side of the diodes in the schematic.
C6 is connected R18 to and C7 is connected to R11.
Not that it matters circuit-wise...

Somewhere on his site he does explain why numbers Q1,Q2,Q3,Q4 in reverse order.

Got the booster wired in tonight but now I'm getting a weird oscillation. It only happens when I have my mini-amp and the big muff both plugged into the power supply. If one or the other has a battery in, the oscillation goes away.

Gotta figure that out but otherwise I'm happy with the revisions.

Update: I'm going to fix some wiring inside tonight. I've got grounds all over, I tapped off the 9V jack for the booster power feed, etc. If after cleaning up it still oscillates, i'll go back to the drawing board. I will say this: before I hardwired the boost in front of the muff, I had no issues with the muff, my marshall mini-amp and other pedals plugged into the power supply with daisy chain plugs. The boost had no power jack so it was running off the battery. So if I eliminate wiring issues/ground lead dress, i'll focus on the boost portion of the revised circuit.