big muff super mods

[gdmart]

I was able to get a 1978 big muff on ebay and it will need some work to make it tone worthy again.Id like to know how to get massive fuzz,forever violin sustain but still keep reasonable bass and clairity. what mods are really necessary,for a super big muff. I have probably 200 silicon npn transistors none of which seem to be mentioned ever in this forum,what makes one transistor sound good and another sound bad. are there certain transistor specs that should be minimum standards.what are these standards??? Again thanks to this forum for the great help and assistance

[R.G.]

what makes one transistor sound good and another sound bad.

Linearity and freedom from noise defects. However, in the muff circuit, the circuit itself obscures most of the transistor characteristics for 99 out of 100 silicon transistors with gains over 100. The differences between devices will be subtle if you can even hear them.

are there certain transistor specs that should be minimum standards.what are these standards???

No. There is no substitute for knowing what the transistors do in the circuit. There are even tricks for lowering gain for certain circuits; look up "piggybacking" in the archives.

Well, OK, you have to have enough gain, usually over 100, and enough voltage, which is usally over 10V or so for 9V powered effects, but it's hard to get transistors that don't do that today.

That being said, I am obligated to put in Keen's Second Law: when in doubt, use a 2N5088.

[gdmart]

I just got the big muff in the mail and I smell big fish !The pcb inside says eh 1332.I dont see transistors either,but there is a rc 4558nb-rt7830 and a lm 741cn What do I have here??? anyone know by the eh-1332??

[RDV]

You have what's commonly known as an"opamp Big Muff". I like them.

RDV

[gdmart]

never heard of it ,what do you like?does it sound similiar to the transistor version? what would you do to get more from this model.Where can I find a correct schematic so I can make sure I start stock.  thanks

[cd]

I would trace out your pedal first, the op-amp Big Muff does not have a known correct schematic circulating.

[RDV]

never heard of it ,what do you like?does it sound similiar to the transistor version? what would you do to get more from this model.Where can I find a correct schematic so I can make sure I start stock.  thanks

Different sound. More metalish, but will still mush out. It was part of the inspiration for my HMP.

RDV

[gdmart]

I found a similiar version  schematic with 3 opamps.mine is a 2 opamp version.
jack orman said it was only made for a while ,and wasnt to popular.cant wait to hear what it does though.does anyone know if it will still get that violin type sustain? on opamp type layouts does the input and output caps still play a big role? what eles can be done? ,does changing the opamp do much as far as the sound,like changing out transistors? when you say mush out what are you speaking of?

[tcobretti]

This appears to be a schematic for the op-amp BM.

http://www.geocities.com/j4_student/bigmuffopamp.gif

[cd]

This appears to be a schematic for the op-amp BM.

http://www.geocities.com/j4_student/bigmuffopamp.gif

Nope.  Doesn't work, contains errors.  Notice I used "known correct" above

[gdmart]

cd hello, what about this layout is not correct?.Why does mine have only 2 opamps and the schematic shows 3 ,I mean to say, can you tell me the function of the 3 ,compared to 2 opamps,so I can learn

[cd]

cd hello, what about this layout is not correct?.Why does mine have only 2 opamps and the schematic shows 3 ,I mean to say, can you tell me the function of the 3 ,compared to 2 opamps,so I can learn

What type of opamps does yours have?  The incorrect schematic shows three, but one is a dual opamp (4558) so there would only be two chips on the PCB.  So if you have two chips, that's normal.

Can you take detailed photos of the top and bottom of the board?

[RDV]

...when you say mush out what are you speaking of?

The typical sound of a high gain fuzz when the gain is turned up.

RDV

[gdmart]

Ill try to get a few close up pics in a day or two.should I post them here or link to a web page,which is better

[bwanasonic]

Why do you want to hack the thing up if you just got it? Does it not sound to your liking? There are a few people on this board who might be willing to take it off your hands if that is the case    I usually wait to hear how a pedal sounds before I start planning the mods!  :lol:  Strange as it might seem, many commercial pedals sound just fine without any modification neccessary!

Kerry M

[gdmart]

well I bought this thinking it was a 4 transistor version,which in my opinion needs some help.I bought it to tinker on you see.The guy said it had been  modded and needed repair,so who needed to listen anyway.
when I opened it up to my suprize it was an opamp version.In my quest to tinker i need to learn as much as possible  about this pedal so i will hack it back to stock,(thats why Im looking for a schematic) un doing the hacked job from the prior hacker.Then ill listen to it and deside if i like it or not,If I dont Ill get rid of it.I think all pedals need modding,that way Ill always have something to do on sunday afternoons

[bwanasonic]

I was set on trying to build the 4 transistor version myself, but after meeting some rabid opamp version fans, I'm curious.

Kerry M

[bobbletrox]

I'd love to see a PCB layout for this.  Or even just a clear pic of the top and bottom of the circuitboard.

I'm pretty sure EH switched to opamps so they could get better quality control from unit to unit.  An interesting mod would be to put in IC sockets and test out different opamps.  The 4558 could be replaced by a burr-brown for instance.  The 741 is a single opamp, but I'm not sure what's available that would be an improvement.

Don't forget, you can always fool around with the diodes too.  LEDs would probably give interesting results!

[gdmart]

If its not a link youll have to copy and paste Ive checked and not all the values are the same on the schematic    coments welcome    
 


     http://buildaband.tripod.com/bigmuff/

[petemoore]

I still don't have a decent BMP clone!!!
 I have parts enough to build OA or discrete ones...
 What should I do?
 I 'tried' the transistor version, muddy, might have not been 'right'...bass player loved it...