Which pots are in an original V4 opamp Big Muff? Schematics are inconsistent.

[Delicieuxz]

The various schematics out there have many different claims on them, including:


sustain - 10K - linear
tone - 10K - linear
volume - 100k - logarithmic


sustain - 10K - linear
tone - 10K - linear
volume - 100k - linear


sustain - 10K - linear
tone - 10K - linear
volume - 50k - linear


sustain - 10K - logarithmic
tone - 10K - linear
volume - 10k - logarithmic


sustain - 10K - linear
tone - 10K - linear
volume - 50k - logarithmic


sustain - 10K - linear
tone - 10K - linear
volume - 10k - linear


sustain - 100K - logarithmic
tone - 100K - linear
volume - 100k - logarithmic


That last one is the BYOC opamp Muff clone, which they claim is an exact clone but, from owning 3 originals and the BYOC, I know that something's off with the BYOC by how it sounds.

[fowl]

From Kit Rae's site:

The volume pot was usually linear taper 100k, although I have seen one with a 50k pot. Tone and sustain pots were 10k.

I tend to trust his Big Muff info.  I'm pretty sure the transistor muffs used 100K linear pots always, or nearly always.  Good guess he means linear taper for the 10K pots also.

[anotherjim]

I noticed Sustain and Volume can be log or lin but traditional was linear (cheaper!) although log ought to be easier to fine tune. Tone can't be log - it should be balanced between bass & treble at 12 o'clock.
A linear pot, to some extent, gets a partial log taper by the load impedance on the wiper. 100k feels it more than 10k does.
Opamps low output impedance means that stage isn't affected by the load impedance on it like the BJT originals are so the Sustain & Tone pots are rescaled from 100k to 10k for less noise. The output doesn't have a recovery amp after the tone pot so the Volume pot should remain 100k. If was 10k it would load the tone pot and drop some volume at 12 o'clock but it would also change the taper of the tone control from either side of centre maybe giving it a smoother adjustment feel. There is a fixed 100k resistor loading the Volume wiper which would lend some log feel to a 100k lin pot but have no effect on a 10k pot.

[Mark Hammer]

Personally, I don't think it really matters.  Mike Matthews bought whatever parts he got a good deal on, and used them.  In recent decades, greater consistency in both supply and manufacture has been achieved, but then those aren't the issues people seem to be interested in.  And though EHX has "replicated/reissued" some issues, how representative are the reissues of what your friend's original pedal from that era sounds like?  We have no idea.

I am reticent to place much faith in the issue-to-issue differences that many find so crucial.  In a great many cases, people find ONE pedal from era X and another from era Y, and draw strong inferences about their audible differences, and the basis for them, to the complete neglect of the MANY component tolerances in the rest of the circuit.  Mike Matthews himself noted that, during the '70s, you could take any 4 consecutively produced Big Muffs off the line and they would all sound different from each other, even though they ostensibly shared the same circuit design and nominal component values.  Get me at least 10 pedals from each of two issues, listen to them critically, and identify what all pedals from a given issue share in common, sonically, and then contrast the issues.

As for pot taper, unless you're spending big bucks (which Mike tended not to do), pot resistances and tapers are largely aspirational.  If you get exactly 100k, and 50k on each side of the midpoint on a linear 100k pot, I salute your good fortune.  It might be a good day to buy a lottery ticket or ask for a raise.  If the way you use a given control makes it hard to find your own personal sweet spot, then a change in taper might be helpful.  But taper only changes dialability, not functionality.  If it works fine, why change?

[Rob Strand]

You can see in these examples that the Sustain and Tone pots are the same.  It's fairly unambiguous the Tone pot is linear so it follows the Sustain pot is also linear.

V4 1977



https://reverb.com/price-guide/guide/21367-electro-harmonix-big-muff-pi-v4-op-amp-1970s-silver



From that and fowls quote from Kit Rae, pots are all linear.

[Delicieuxz]

Here's another bit of info from Kit Rae's website.

"V4 and V5 op-amp Big Muffs were made with 10k linear taper Sustain and Tone pots (marked PO130 or ZA2124). The Volume pot was 100k linear (marked XM2184 or PO150), but some early V4's had 50k volume pots and some late model V5s had 150k."

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

Personally, I don't think it really matters.  Mike Matthews bought whatever parts he got a good deal on, and used them.  In recent decades, greater consistency in both supply and manufacture has been achieved, but then those aren't the issues people seem to be interested in.  And though EHX has "replicated/reissued" some issues, how representative are the reissues of what your friend's original pedal from that era sounds like?  We have no idea.

I am reticent to place much faith in the issue-to-issue differences that many find so crucial.  In a great many cases, people find ONE pedal from era X and another from era Y, and draw strong inferences about their audible differences, and the basis for them, to the complete neglect of the MANY component tolerances in the rest of the circuit.  Mike Matthews himself noted that, during the '70s, you could take any 4 consecutively produced Big Muffs off the line and they would all sound different from each other, even though they ostensibly shared the same circuit design and nominal component values.  Get me at least 10 pedals from each of two issues, listen to them critically, and identify what all pedals from a given issue share in common, sonically, and then contrast the issues.

As for pot taper, unless you're spending big bucks (which Mike tended not to do), pot resistances and tapers are largely aspirational.  If you get exactly 100k, and 50k on each side of the midpoint on a linear 100k pot, I salute your good fortune.  It might be a good day to buy a lottery ticket or ask for a raise.  If the way you use a given control makes it hard to find your own personal sweet spot, then a change in taper might be helpful.  But taper only changes dialability, not functionality.  If it works fine, why change?

Hi Mark. My interest is in rehousing a Little Big Muff into a new chassis with Volume, Tone, and Sustain knobs while not throwing off the resonant frequency compared to the original pedal. I'm not sure how much different value pots would shift the resonant frequency, but when I changed the pots in my 1982 JCM 800, the higher-value newer pots really changed the voice of the amp, and not for the better. The amp became much less sweet-sounding. I plan to put the original lower-value pots back into that amp.

I'm also wondering whether I should add the V5 Big Muff's Tone Bypass switch for the same reason - in case its mere presence shifts the resonant frequency, which I want to avoid.


A related question I have is, does adding a 500K resistor across the lugs of a 500K potentiometer, to produce a pot with a resistance of about 250K, result in the same effect on the resonant frequency of a circuit as if using a native 250K pot?

[Mark Hammer]

WHAT "resonant frequency"?  That part is not clear to me.

But here's a suggestion.  Make a decent direct recording (i.e., pedal to recording device) of the pedal's sound before you do any rehousing or mods, so that you can compare.  Two reasons.  First, if nailing that tone is important to you, you want to make sure it is replicated.  Second, the rehousing will take more time than your acoustic memory buffer can retain things.  You might THINK it sounds different when it doesn't or think it sounds identical when it doesn't.

The Tone bypass is interesting, but nothing life-changing.  It basically eliminates the midscoop.  You should take a gander at the various Tone control mods that Jack Orman has written up in the Labnotes section of his AMZ site.

Also, bear in mind that what a pot says on the outside, is not necessarily what it IS on the inside.  A pot labeled 250k might be 217k.  Measure the component itself, before deciding on what parallel values would get you what you want.