Resurrecting Richard kaplan's "Bigger Muff"

[Gus]

Another set of GUESSES

Looked at the Prem web site it might be a 20VA transformer.  I measured a tube and did a fast scaling of the picture and got close to the dimensions in the link.
http://www.premmagnetics.com/Products/Details/SPW-611-D
Note it has a dual primary.  Maybe one primary winding is used to power the transformer and the other for the B+ supply, not the best thing to do.  It is not something I would build

PRR might want to post about this

Not many parts on the PS PCB
A crude 9vdc power supply was a 6.3VDC full wave rectified 6.3VAC X 1.414= 8.9VDC with ripple maybe it is a 12.6V tube heater at about 9VDC or a 6.3V at 9VDC
OR it could be 12.6VAC powers the heater and a diode(s) is used to the two smaller caps to filter the DC.  Problem is I can see any diodes in the picture   One diode, 12.6 x .7 = about 9VDC

From the picture the output electro looks like it does not have the - band pointing at the last transistor stage if the + is pointing to the transistor I would guess a NPN version HOWEVER if they are not polarized it is still a 50 50 guess to NPN or PNP build

If the 430K is missing base to +9VDC the last stage might be a crude noise gate distortion stage.  If the signal is big enough it will turn the transistor on in a distorted way

The input 39K? body might be under the sustain control shaft

[illuminatiNPS]

Prem the transformer company confirmed the transformer:


0102024-002
prem8732

Input 115v in paralell 230v series

output:
3 secondary windings.
2 are same at 12vac at 50ma
3rd 200vac at 100ma

[Gus]

.1amp x 200V = 20VA
12V x .05amp = .6VA

21.2VA.  I was close with the 20VA rating guess

200VAC at 100ma is way more then needed B+ current for a small signal tube

Now this is a puzzle 100ma(50ma + 50ma) at 12VAC.
A 12ax7 is rated 150ma at 12.6V
Maybe the transformer is being used beyond it current rating at 12VAC 
The 200V winding should not be stressed I would guess about 1ma

R.G. would this allow more current to be drawn from the 12VAC without overheating the transformer?

BMP like circuits without a led should be under 2ma

I wonder what tube it is?

EDIT one could use a "Real Mctube" type power supply with a voltage doubler instead of a full wave bridge

[illuminatiNPS]

Gus,

   I know we have been kind of ignoring that "Harmo" word on the left side of the board. But part of me is starting to think it has to do with the tube. That is not an E next to the "Harmo", its a dash. Part of what comes before it is covered by duct tape. I'm think the word stands for Harmonic Distortion/Even Order Harmonic provided by the tube. This makes sense because 1) Wes Borland said the pedal "was always on" and 2) Kaplan said when he made the 2nd one for Andreas he included a "hard on/off" switch. Also evenb order harmonic distortion includes octaves which essential would make the Big Muff sound 'fatter/bigger". I am starting to believe the middle switch on the board activates the tube stage.

Also if you looking closely at the volume pot, you see a pink wire attached. If you follow it under the perfboard, you can see that the wire travels underneath the brown resistor to the switch. Coincidentally, there is another pink wire coming from that switch heading towards the sustain Pot. Maybe the pink wires represent Input and output.  Good possibility the tube is the first think the signal hits. And with that pink wire traveling from Vol to the switch, that could be the feedback loop that creates feedback/oscillation with only the pedal being plugged into an amp without a guitar, which is activated by the red switch

Still doesn't explain the rogue brown resistor traveling from left to right, unless of course that is the missing 430k from Q1.



 

[illuminatiNPS]

Very confident that the word below the red switch says "EFFECT" not ECCFat. Thanks to my buddy with graffiti experience.

[Gus]

Bump
I am surprised by the small amount of posts in this thread. 
A number of things have been figured out, still a few unknowns

[Derringer]

I think it's just difficult for most of us to test out the ideas being tossed around because, I assume, most of us don't have the supplies lying around to easily wire up a 12AX? with 100+ plate volts.

I have been keeping tabs on this thread though .. just don't have anything to add really.

[Rob Strand]

The subject title is enough to scare anyone.

[Gus]

Anyone know what the power supply PCB might have been from?

It looks like it might have three caps on it stock the two small electros(I see PCB traces to the two in the picture) and the blue Mallory, looks like it has print on the PCB under the bigger blue cap.

The reason I ask is this will give a hint to how the circuit is powered and how the circuit reacts.
I don't see any diodes, could it be the two 12VAC windings are rectified(two small blue caps)so the PCB has two about 12DC outputs with another output somewhere around 200VDC

[BuGG]

I think it's just difficult for most of us to test out the ideas being tossed around because, I assume, most of us don't have the supplies lying around to easily wire up a 12AX? with 100+ plate volts.

I'm using a little Nixie SMPS to bump 12VDC up to around 190VDC (unloaded)....

[Derringer]

cool BuGG, any cool results mucking around with permutations of this circuit?

[BuGG]

Almost done....   

[stonerbox]

Almost done....   

Me right now ↓

[caspercody]

Sorry, nothing to add. Just want to know what BuGG's results are.

[BuGG]

Oh yeah, it's up and going like it should.   

Just have to apply graphics to the enclosure then this one will be on it's way to Nick (illuminatiNPS).

[Derringer]

Looks awesome BuGG!
a sound sample would be awesome if possible!

what design did you go with ? where do the triodes sit in the signal path?

[ulysses]

bugg what schem are you working from?

[leito79]

Is there ever going to be a layout/schematic for this? Or at least some pointers such as: What BMP version was used (russian, triangle, ram´s head, etc)? Transistors? Values of coupling caps (since is intended for lower tunings)? Where in the circuit are the tube triode stages applied? Man I friggin´love that sick over-the-top guitar tones from Sepultura and early Korn records, the mystery is eating me inside!!!!

[illuminatiNPS]

Yes, of course I'll give some pointers. It follows a ram's head layout/schematic. The mods done to the muff board are mostly in the capacitors. The input cap  and ouput cap is  10uf. the coupling cap that is at the end of Q2 is also 10uf. This can be seen by the 3 grey electrolytics in the original image. The feedback caps which are normally around 470pf are dropped down to 47pf for extra buzz(these are the 3 big lollipop looking caps on the board). the 12ax7 gain stage sits between the 2 diode clipping stage. Being that its high voltage, the transformer powers the anode, the heater, and the muff board itself. The original schematic calls for 125vdc at the plate, so you will  need 200+vdc for b+ or more if you use an SMPS instead. Its is single triode and heaters are in series. The brown resistor running across the board is most likely a 2ns feedback path that caused extra fuzz as well s as feedback and ooscillation when the strings are muted, much like a Fuzz factory. This can be heard on Life is Peachy and Roots.

  I apologize for not responding to the hungry requests on the pedal. I have since built one for Ross Robinson himself as well as building for an indigo Ranch engineer and one for Soulfly. If you wish to attempt to build one just contact me at nickspera@hotmail.com or 954-802-1969 for notes/layout etc.. merry Xmas everyone   

[Hatredman]

This interview?

https://www.youtube.com/watch?v=VKv8tmLPZEE