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Vintage threads from the first ten years

Big Muff Pi Diffrences.

6/11/1997 9:07 AM
Adam Frankowski	Big Muff Pi Diffrences. I just recently bought a Big Muff Pi used off of someone.. It is not the reissue, but when I popped it open I saw Op-Amps inside. The original Big Muff's used transistors, correct? Is there a big diffrence in tone? I am quite happy with it.. But maybe a Big Muff based on transistors would sound better? Also, Is there any mods that can be done to a big muff.. I was thinking of adding an LED light and maybe increasing the bottom end if possible. Thanks

6/11/1997 9:07 AM

Adam Frankowski

Big Muff Pi Diffrences.

I just recently bought a Big Muff Pi used off of
someone.. It is not the reissue, but when I popped it open I saw Op-Amps inside.

The original Big Muff's used transistors, correct?

Is there a big diffrence in tone? I am quite happy with it.. But maybe a Big Muff based on transistors would sound better?

Also, Is there any mods that can be done to a big muff.. I was thinking of adding an LED light and maybe increasing the bottom end if possible.

Thanks

6/11/1997 10:43 AM
R.G. Keen	There is one version that is opamp based, with three pairs of diodes for clipping. The first versions were transistor, yes. I don't know about big differences in tone, but the potential is there. Of course, if you're happy with it, why go walkabout?

6/11/1997 11:48 AM
Adam Frankowski	>I don't know about big differences in tone, but >the potential is there. Of course, if you're happy >with it, why go walkabout? Well I was just wondering if the Big Muff could be made to sound even better. Maybe I will try building one from the schematic I have (the one you probally made) and compare them. In general are all Big Muffs full of noise? This one seems to be pretty noisey, I was thinking maybe due to the op-amps.

6/11/1997 11:48 AM

Adam Frankowski

>I don't know about big differences in tone, but >the potential is there. Of course, if you're happy >with it, why go walkabout?

Well I was just wondering if the Big Muff could be made to sound even better. Maybe I will try building one from the schematic I have (the one you probally made) and compare them.

In general are all Big Muffs full of noise? This one seems to be pretty noisey, I was thinking maybe due to the op-amps.

6/11/1997 12:29 PM
R.G. Keen	Pretty much any device that amplifies signals a lot is noisy, just because even the smallest noise at the input is amplified by the whole gain of the unit. This is worse for fuzz boxes because the real signal is clipped off, while the noise is not, so it is amplified by the full amount. But... in your case, it's the opamp. That's a 741, which does not have stellar noise performance. Whip in a TL071 and see what you think. You can often help by using metal film resistors in the input circuits.

6/11/1997 12:29 PM

R.G. Keen

Pretty much any device that amplifies signals a lot is noisy, just because even the smallest noise at the input is amplified by the whole gain of the unit. This is worse for fuzz boxes because the real signal is clipped off, while the noise is not, so it is amplified by the full amount.

But... in your case, it's the opamp. That's a 741, which does not have stellar noise performance. Whip in a TL071 and see what you think.

You can often help by using metal film resistors in the input circuits.

8/18/1997 4:54 PM
Paradiddle	Big Muff Pi Diffrences!!. Ok,.....I have built a few of these suckers now and i'm quite happy with them,...the Muff that RG has transcribed has a lower frequency bandwidth than the one i transcribed the EH-3003 early model however this one has more gain and more upper frequencies than its counterpart,....RG's make i have not seen the OP-amp version though i would love to see the transcription off it,.... and just for the book what the number is that is on the PC board. To get more bass you could just alter the tone cap in the tone section of the last stage. If you want a copy off the EH-3003 schematic you can give me an email and i will send it........ Later, PD

8/18/1997 4:54 PM

Paradiddle

Big Muff Pi Diffrences!!.

Ok,.....I have built a few of these suckers
now and i'm quite happy with them,...the Muff that RG has transcribed has a lower frequency bandwidth than the one i transcribed the EH-3003 early model
however this one has more gain and more upper frequencies than its counterpart,....RG's make i have not seen the OP-amp version though i would love to see the transcription off it,....
and just for the book what the number is that is on the PC board. To get more bass you could just alter the tone cap in the tone section of the
last stage. If you want a copy off the EH-3003 schematic you can give me an email and i will send it........
Later,
PD

6/21/1997 10:52 AM
Charles	Re: Big Muff Pi Diffrences. Adam, I've got one of those! I really don't use it too much (my tastes have changed) but I did experiment with all sorts of op amps in it. I saw the reply by RG and he's right on, but there are lots of others. Your ears will decide which is best for you. The chips sre fairly inexpensive, so the experimentation won't break the bank. For sure.. one of the opamps is a 741, which is available in about a jillion flavors. I found some that were noisey but had a slightly better low end (a little rumbly). I seem to remember the other opamp is a dual version. I don't have my parts in front of me but I think it is the common dual-741. There's a whole host of them out there in the market too. You can add sockets to make the changeout easy. Also the EH boxes have notoriously poor wire connections, you might want to redo those, and... the flux they used is usually all over the place. Denatured alchohol and a toothbrush (old please, yuech) cleans that off and can improve the noise a little.

6/21/1997 10:52 AM

Charles

Re: Big Muff Pi Diffrences.

Adam,

I've got one of those! I really don't use it too much (my tastes have changed) but I did experiment with all sorts of op amps in it. I saw the reply by RG and he's right on, but there are lots of others. Your ears will decide which is best for you. The chips sre fairly inexpensive, so the experimentation won't break the bank.

For sure.. one of the opamps is a 741, which is available in about a jillion flavors. I found some that were noisey but had a slightly better low end (a little rumbly). I seem to remember the other opamp is a dual version. I don't have my parts in front of me but I think it is the common dual-741. There's a whole host of them out there in the market too. You can add sockets to make the changeout easy. Also the EH boxes have notoriously poor wire connections, you might want to redo those, and... the flux they used is usually all over the place. Denatured alchohol and a toothbrush (old please, yuech) cleans that off and can improve the noise a little.

6/22/1997 8:40 PM
Mark Hammer	Can't say what the tonal differences are between the op-amp and transistor versions. My guess is that any such differences are likely to wash out when one considers the variation in transistors, caps, diodes, etc. that E-H likely used. You should bear in mind that diodes show a fair amount of variation in their voltage drop. There is the usual difference between silicon and germanium but even within standard 1N914 silicon types, any given diode in a pack of 20 or so can easily show a meter reading between .52 to .7v clipping point. When you use one pair of back to back diodes in a conventional clipping circuit, such variation may provide small, marginally audible differences which wash out when you turn the gain up higher or lower, and EQ it. The BMP, however, has 3 such pairs cascaded, which I suspect can have a more potent effect on cumulative clipping, and tone. I'd be curious to see if there are any folks out there who have measured the diode characteristics in "winner" and "so-so" BMP's. Given the number of other active and passive components in the mix, finding the "magic" combination of parts for a BMP is probably more difficult than finding the combination for a winning TS-808 (or at least as difficult). Ultimately, what you go for is what your ears prefer. I find that fuzzes can frequently be made to behave differently with the right amount, and kind, of pre and post eq-ing. Noise characteristics can often be improved by goosing the signal ahead of the fuzz (cleanly), and then turning down the sensitivity of the fuzz itself. Sometimes, prudent EQ-ing can do that job too. E.g., a nice hefty lower midrange boost from a graphic or parametric EQ in the 300-800hz range can elicit a wonderfully "gronky" (think Billy Gibbons) tone from many overdrives, and provide an overall signal- level increase which allows you to set the sensitivity/gain/fuzz/drive control a bit lower and lower the noise component generated by the fuzz itself at its output. If you check the schematic, you'll see that the tone control consists of single pole (RC) high-pass and low-pass filters with a 100k pot to pan between them. The "cutoff" values (i.e., the cap values) are selected so that when the tone control is set to the middle, it is equivalent to a "flat" or "tone bypass" setting. If you want more of "scooped-mid" or "death metal", all you have to do is select cap values such that there is a larger gap between the rolloffs of the high-pass and low-pass sections. This doesn't increase the bass like some of the BOSS units that have active EQ-ing. Rather, it simply robs the signal of more of the midrange. If you would like more flexibility, then consider installing a DPDT toggle (or slide) switch, that selects between the stock cap values, and those that deliver the "scooped" tone. I haven't experimented with the values, but a reasonable place to start is to select cap values about 30% smaller for the high-pass section, and 30% larger for the low-pass section. Halfing or doubling the value changes the rolloff by a full octave, which may result in too pronounced a mid- scoop. I suppose it may have some value to someone as a valid sound, but do bear in mind that pushing the envelope a bit too much with the tone control will start to become useless as a variable control, yielding only low end fart, mosquito buzz, or a combination of the two, rather than the somewhat smoother sweep the BMP normally has. Okay. Carry on.

6/22/1997 8:40 PM

Mark Hammer

Can't say what the tonal differences are
between the op-amp and transistor versions.
My guess is that any such differences are
likely to wash out when one considers the
variation in transistors, caps, diodes, etc.
that E-H likely used. You should bear in
mind that diodes show a fair amount of
variation in their voltage drop. There is
the usual difference between silicon and
germanium but even within standard 1N914
silicon types, any given diode in a pack of
20 or so can easily show a meter reading
between .52 to .7v clipping point. When you
use one pair of back to back diodes in a
conventional clipping circuit, such variation
may provide small, marginally audible
differences which wash out when you turn the
gain up higher or lower, and EQ it. The BMP,
however, has 3 such pairs cascaded, which
I suspect can have a more potent effect on
cumulative clipping, and tone. I'd be
curious to see if there are any folks out
there who have measured the diode
characteristics in "winner" and "so-so" BMP's.

Given the number of other active and passive
components in the mix, finding the "magic"
combination of parts for a BMP is probably
more difficult than finding the combination
for a winning TS-808 (or at least *as*
difficult). Ultimately, what you go for is
what your ears prefer. I find that fuzzes
can frequently be made to behave differently
with the right amount, and kind, of pre and
post eq-ing. Noise characteristics can often
be improved by goosing the signal ahead of the
fuzz (cleanly), and then turning down the
sensitivity of the fuzz itself. Sometimes,
prudent EQ-ing can do that job too. E.g.,
a nice hefty lower midrange boost from a
graphic or parametric EQ in the 300-800hz
range can elicit a wonderfully "gronky"
(think Billy Gibbons) tone from many
overdrives, and provide an overall signal-
level increase which allows you to set the
sensitivity/gain/fuzz/drive control a bit
lower and lower the noise component generated
by the fuzz itself at its output.

If you check the schematic, you'll see that
the tone control consists of single pole
(RC) high-pass and low-pass filters with a
100k pot to pan between them. The "cutoff"
values (i.e., the cap values) are selected
so that when the tone control is set to the
middle, it is equivalent to a "flat" or
"tone bypass" setting. If you want more of
"scooped-mid" or "death metal", all you have to
do is select cap values such that there is a
larger gap between the rolloffs of the high-pass
and low-pass sections. This doesn't increase the
bass like some of the BOSS units that have active
EQ-ing. Rather, it simply robs the signal of more
of the midrange. If you would like more
flexibility, then consider installing a DPDT toggle
(or slide) switch, that selects between the stock
cap values, and those that deliver the "scooped"
tone.

I haven't experimented with the values, but a
reasonable place to start is to select cap values
about 30% smaller for the high-pass section, and
30% larger for the low-pass section. Halfing or
doubling the value changes the rolloff by a full
octave, which may result in too pronounced a mid-
scoop. I suppose it may have some value to
*someone* as a valid sound, but do bear in mind
that pushing the envelope a bit too much with
the tone control will start to become useless as
a *variable* control, yielding only low end fart,
mosquito buzz, or a combination of the two, rather
than the somewhat smoother sweep the BMP normally
has.

Okay. Carry on.

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