EH NYC Big Muff: Anyone know of any mods?

[Henry89789]

Anyone know of any mods for the NYC Big Muff?   Especially mods that quiet it down. Also read about mods that give the pedal a "creamy"  tone. Anyone know about that.  Thanks.

[runmikeyrun]

search the forum, tons of stuff will come up.  Search for technology of the big muff, it's got a lot of really helpful tips on what does what in the circuit.

[Henry89789]

Yes that is the problem. too much material to sort through and most of it presented in a way understandable mostly to electronic engineers.  I am used to Brian Wampler's book which tells you which capacitors, diodes and resistors to change and the value to change them to.  His book has nothing on the NYC Big Muff though. I was hoping someone could suggest some specific changes and tell me what those changes do.

[blooze_man]

Add a 47k resistor in parallel to the 100k to ground in each of the clipping stages. This quiets it alot, but only sounds good with the "sustain" at higher settings.

[petemoore]

  Notice the commonalities of the circuit topologies.
   Stages are actually quite similar if the voicing caps and diodes are removed from the clipping stages.
  Each stage's Emitter resistor is a good place to start 'large' and piggyback resistors [how I decided to have hardwired yet selectable Eresistor]. Low gain setting [high R value] can be made full gain with an AC bypass cap, no-one seems to like it...that too could have a cap value selection and variable R of some kind to adjust voicing...but going back to no Ebypass cap seemed to be what I remember those who have tried it reported doing.
   The first transistors output is multi-multiplied, so gain increase here equates to a lot more gain being generated later.
  The BMP is a good study in 'whatever...they were all sounding a bit different and the parts values have been known to 'drift' from unit to unit, ballpark value resistors and transistors that will work make a strong boost-distortion pedal tone. Four transistors may seem more than is necessary to get muff amount of distortion, but it works and is easy to whip together with just about whatever is 'there' [the sustain pots 'overdrive' is sufficient that even if it's a 'weak' BMP it is still a strong boost-distorter.
   A fifth stage was added to Billy's BMP in 1972, a couple LPB types were added, one box hung out of the input of the BMP and caused major noise-sustain-OD grind-tone with lots of feedback, but uncontrollable feedback if not somehow 'stopped' [turn the guitar of distortion off].
  Suggestion: Build stage 1 so you can mess with it's values where needed [probably just the E resistor]. Build stage 2 and 3 on a breadboard, By putting the basic boost stages on a BMP Board, then feeding the distortion generating circuits on a BB [the diode/transistor stages], you could mess with basically all the 'good stuff' to mess with on a BMP p[retty easily.
   See FAQ on modifying, look at the diode configurations etc., perhaps a more open treble feed early or bass cut early would be in you desired result...everyones desire is different, as well as the 'other gear'. 

[Henry89789]

Blooze_man:   Thanks. Your suggestions are something I can try.  How can I identify the clipping stages?   Are all the 100k resistors associated with the clipping stages?   I saw you are in Anchorage.  I lived in Fairbanks in the late 70s. Tried to work on the pipeline.  Went through the Anchorage airport once. I remember all the huge stuffed animals in glass cases in the lobby. Do they still have those ?

petemoore:   Huh?!?   "the commonalities of the circuit topologies"      I only understand topology in regard to geography ....  You wrote all that because of what I said about electronic engineers, right?   Anyway, thanks for taking the time to write it.  I wish I understood it all.  BTW:  How do you identify the "emitter resistors"?

[runmikeyrun]

Sounds like you might be in a bit over your head.  You'll need to study a simple one transistorfuzz to understand the basics before jumping into the muff.  Then once you understand that you'll see the BMP is just 3 of those put together, with a few additions.  You're going to have to do a lot of reading to learn what is doing what.  Print it out and take it to your workbench, and reference it while you experiment with the circuit.  Then things will start making sense.

To answer your questions, the emitter resistor comes off of the emitter of the transistor and goes to ground.  Usually the "bottom" leg of the transistor on the schematic.  Lower values will usually increase gain of the transistor, but go too low and you can make it unstable and it will sound terrible.  The clipping occurs in the diodes of stages two and three.  Playing with the diode types changes the sound of the distortion.  You can also use LEDs which are technically diodes.  

I suggest you socket the transistors, clipping diodes, coupling caps, input cap, caps in series with the diodes, and caps parallel to the diodes.  If you are unfamiliar with any of those terms, do a forum search.  This allows you a lot of flexibility because you can change components in the circuit without having to unsolder and solder all the time.  The sockets come on a strip, you break them off one at a time and solder them in the hole where the component leg goes.  Then the components just push into the socket and are easily removed/reinstalled.  

Order a bunch of different diodes from a place like Small Bear, they are cheap and they all sound a little bit different than each other.  Get some germanium, 4001s, 914s, LEDs, etc.  Also get some different value caps- a range of small values (100pF-0.01uF) and larger ones (0.01-1.0 uF)  Several different transistors are options too, but i've found they don't make much difference.  2N3904, 2N5088, 2N5089 are all options.  For $20-30 you can get a large amount of components and you'll have the ability to spend countless hours experimenting.

This is a good link on where to start experimenting with the BMP:

http://generalguitargadgets.com/pdf/ggg_bmp_mods.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

Good luck, and have fun!

[Henry89789]

runmikeyrun:

Thanks for that reply.  The pdf document in the link is great and exactly what I was looking for. I googled "Big muff mods" and looked at a lot of the results but didn't find that one. Your suggestions re: studying a simple one transistor fuzz,  sockets, and components to buy are also very helpful.

[boog]

you can check these out as well. one of the things that's wonderful about the BMP is that the circuit has never really changed. component values and that whole PNP v. NPN transistor thing, but the gist of the thing is the first link below (just remember that new BMP's are NPN ie negative ground). for most of the mods you just need to be able to follow directions and make good mechanical connections (add some switches). i too have difficulty comprehending exactly what is going on (still a whole bunch of magic jellybean field), but i've gotten to the point where i can identify where stuff is sposed to happen. also: GGG has the best (easiest to read) schematics for the BMP. have fun with this thing!

http://www.kitrae.net/music/big_muff_guts.html#Circuit

http://rkerkhof.ruhosting.nl/Taas/Mods/Big%20Muff.htm

http://www.diystompboxes.com/smfforum/index.php?topic=78111.0