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Big Muff PI Probs!!Help please!!

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2/7/1997 9:28 AM

***NoCarrier***

Big Muff PI Probs!!Help please!!

Hi,....everyone,...
I have built an EH Big Muff Pi and i'm having a few probs with it.....here's the scoop:
I got the schmatic off the net,....i think it was lepers,..anyway...i was told that
its the orignal schmatic it uses four transistors,.....i built the thing because it was rated very well in the
Harmony Central effects section everyone like it,....when i built it i got nothing
more than a bassy,muffled, distortion,....i went over the schmatic alot to see if i made any
errors but everything checked out ok,....i used a few subsitutes like 2n2904
transistor and 1n34 diodes could this be the problem???......also i'm not sure if
i got the capacitors on the tone section right could that possibly be the problem???
What would be your opinion on the situation???,...i gotta say if this is the distortion
that everybodys raving about then someones gotta stop smokin' bannana peels!!
heheheheheh,...anyway i know i messed up somewhere because everyone
who ive talked to likes the sound of it so any light on the subject is very much appreiciated!!!!!
Thanks alot!
Jeff

2/8/1997 11:48 AM

If, in fact, you did use 2N2904's, then that could be your problem since
they are PNP transistors and the schematic calls for NPN. I built one
from the schematic, as posted, using 2N5088's, and it is VERY nice.
Nice long buzzy sustain, great for Adrian Belew sounds, insect noises,
and charging rhinos. Good gain, great variation in sounds.
Using 2N5089's might be even better since they are supposedly lower
noise, but with the same high gain characteristics. If you compare the
schematic for the Big Muff Pi and Little Big Muff, you will note several
differences in component values although the basic design is essentially
identical. One of the useful differences between the two that might be
worth incorporating is the 100uf cap between the +9v input to the circuit
and ground, which is present in the LBM but not in the BMP.

The diodes you mention are germanium, which have a different voltage
drop (about .25-.27 volts, as opposed to the .5-.57 of silicon diodes).
Mine uses silicon diodes (1N4148 or 1N914), although the schematic does
not really specify which type to use. If the use of appropriate
transistors clears up the problem, I'd be curious about what the use of
germanium diodes does.

The caps in the tone section can be very different from those stated, yet
still provide many usable sounds. The tone control simply pans between
a crude high-pass and a crude low-pass filter, so that one extreme give
a mute sound, and the other gives a thin buzzy sound, and the middle
position gives a balance of each.

Finally, there are quite a few polarized electrolytic caps in the signal
path. Make sure you've observed proper polar orientation on them.

Good luck. Once you've licked the glitches in the circuit, you'll be
glad you invested the time. I've had at least a dozen different fuzzes,
and I like this one a lot. It isn't all purpose, but it accomplishes
its own purpose extremely well.

2/8/1997 4:42 PM

***NoCarrier***

Hey Mark!

Thanks for all the info,.....
I'm using 3904's i used 2n5088's and then changed them to 2n3904 with no
noticeable change in sound all my caps are in right. 1n34 germanium diodes
create more fuzz than there counterparts 1n914 thats the difference
so i'm gonna put an order in at electrosonic in Ottawa and order some transistor whicich
ones are the best for stomp boxes,.......
I will go over my effect box tonight to check to see if everything cool,...
` Thanks,.
Jeff

2/8/1997 6:02 PM
R.G. Keen	What you describe is not the way it should sound. I would guess, long distance, that either you have a capacitor value wrong, pulling out too much treble, or you have a bad connection somewhere - maybe a miswiring in the tone control section? I've built a dozen or so of these, and offer a clone pcb package on my web page. They are quite reproduceable.

2/8/1997 6:19 PM
*NoCarrier*	Thanks,..... Ok well i'm gonna go over it and see if i made a boo boo some where! Its really bassy when i turn the treble up it turns more fuzzy distortion and loses a bit of sustain,....... Jeff

2/10/1997 6:17 AM
Christian Landry	Just as an FYI, the transistors used are BC239. the good old European transistors. Christian

2/10/1997 10:09 AM
*NoCarrier*	Thanks,...BC239's what about the diodes what are they???,....1n914's??? Also could you describe the sound that the muff is sopossed to sound like,...thanks,........ Jeff

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