Big Muff versions - What really matters...

[Hides-His-Eyes]

For resistors it's easier to use a pot. 

yes but what if you don't want to check the pot with a multimeter everytime you found a desired value. these things were "invented" for a reason.

Hey, whatever makes you happy; but it's not a big deal to me to measure one value when I'm decided...

[Projectile]

I was wondering if you changed C1, C4, C7, C12 & C13 (GGG schm). I would have thought changing these coupling caps would also change the bass responce?

According to my calculations and experimentation, the cutoff point of these caps are situated below the audible range at .1uf, so changing them to to any value above .1uf shouldn't make much of a difference. None of the Muff schematics I saw used anything less than .1uf, so the effect of changing them should be pretty minimal. I only tried changing them two at a time because doing all of them at once is a pain to put on a switch, but I only detected a very tiny change in bass response when swapping out two. It was hardly even noticeable. Messing with c6 and c9 produces much more dramatic changes in bass response.

You could theoretically lower the values of the coupling caps well below .1uf if you wanted to remove some of the muddiness of the Muff (as mentioned by alex frias), but my goal here was more to determine what the differences between he schematics, so I didn't go down that path.

This is very usefull for tinkering around with caps, diods and so on:



Also give this doc a try:
http://www.beavisaudio.com/bboard/projects/bbp_DiodeMods.pdf
Especially Jack Orman's Warp Control did a nice job in a muff with one clipping stage.

Thanks, I need to build one of those. I realized near the end of my testing that there were several things I could have built that would have made the process a lot more efficient. Next time.

I'll also check out those diode mods. I messed with the diodes a bit, and wasn't really keen on any of the results, but I didn't ave any schottkys or germaniums lying around, just 1n914s and LEDs.

This thread might help, "Technology of the Big Muff - What Does What?":


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

I hadn't seen this thread. Thanks!

[culturejam]

Great post! Thanks for the taking the time to write up your findings.

I'll have to say that from my own experimentation with the Big Muff (and I've built about 10 of them), the value of R1 can have a big difference on the overall gain. Lower gain = more of the input signal being amplified by the first (boost) stage.

Using a pot in place of R1 is actually a pretty cool mod. You can get crazy gated distortion or much lower gain, almost OD-like tones with the same Muff circuit.

I'm curious to hear if you played around directly with swapping values of R1 in real time to hear the difference. I have one Muff with two values for R1 on an internal dip switch setup, and the difference is pretty clear to my ears (and I do NOT have golden ears).

[Projectile]

Great post! Thanks for the taking the time to write up your findings.

I'll have to say that from my own experimentation with the Big Muff (and I've built about 10 of them), the value of R1 can have a big difference on the overall gain. Lower gain = more of the input signal being amplified by the first (boost) stage.

Using a pot in place of R1 is actually a pretty cool mod. You can get crazy gated distortion or much lower gain, almost OD-like tones with the same Muff circuit.

I'm curious to hear if you played around directly with swapping values of R1 in real time to hear the difference. I have one Muff with two values for R1 on an internal dip switch setup, and the difference is pretty clear to my ears (and I do NOT have golden ears).

You know, it's really interesting you should say that, because the first time I tried swapping out R1 I did notice a huge difference (lots more gain, more bass, dirtier sound).  I originally wrote down in my notes that it was one of the significant parts that noticeably changed the sound. My plan was to put a pot there to experiment with it more, but I didn't have a pot of the right value soldered up and ready to go, so I put the original value back and moved on, planning to come back to it later.

Then, for some reason when I went back the next day and tried to it with a pot, I got nothing. I could turn the pot all the way down to zero and there was no change. "Well that's odd," I thought, because I could have sworn it made a huge difference when I changed that value to something smaller the other day. I double checked everything, and I even ditched the pot and just tried swapping resistor values again. Nothing. It looked to me like I must have somehow made a mistake the day before. For some reason I just couldn't reproduce what I had heard. It has been bothering me ever since.

In the end, I figured it was some strange mistake-- some wires must have gotten crossed somewhere. But now that you tell me changing R1 does in fact have the effect I originally heard, I'm wondering what I did wrong when I went back to test it. Weird.

Looks like I'm going to have to go back and explore this mystery a little better. I may have messed that test up somehow. Thanks for pointing it out! Unfortunately it will be this weekend before I have a chance to play with this circuit again, but I'll be sure to post an update when I get to it.

[clamup1]

Is this also true for the IC versions?

[jefe]

Is this also true for the IC versions?

Not sure which "this" you're referring to, since folks have posted all kinds of mods and preferences in this thread. That said, the IC Big Muff is a different beast entirely, so much (most?) of the info in this thread won't apply.

[DiscoVlad]

With the OA Big muff, you could:

Increase the input coupling capacitor for a bit more bass (or decrease it for less)
change the gain resistors on the opamps...

which may or may not have much effect as it's pretty muddy at low sustain + low end tone settings

Though at a quick glance the biggest changes to the sound would be removing one of the clipping diodes for asymmetric clipping, and/or changing the tone stack e.g. removing the mid scoop or adding the tone bypass circuit.

[clamup1]

sorry for asking such a vague ? the op is saying that you change a few resistors and caps and make one Muff sound like another. the ic versions have less parts. like on the tranny muffs there are two caps at the clipping section (where all the diodes are) the ic version there is only one.

i do have an ic version on the bb but i cant get it to work. i built the russian (tranny) and i want to build an ic version of the same pedal.

[DiscoVlad]

Eh, don't worry about it 

On the IC Big muff the capacitor on the clipping section is there to roll off the high frequencies, larger values should make it a bit more bassy.

These are the Eagle project files for the IC Big Muff I built recently (This is verified working). I've used a 330pF capacitor on the clipping section, and it's pretty muddy, so wouldn't go much larger than that.

Looking at the Green Russian schematic, and the IC BMP schematic, the tone stack is different, maybe trying a green russian stack on the IC version would give a similar sound.

This is probably also relevant:
With the Tone bypass mod, the output of the IC BMP is pure square wave so most of the (whatever little) Big Muff character it has comes from the tone stack.

It certainly doesn't sound like my Sovtek black russian BMP, that's for sure.

[Joe Hart]

Very interesting. I've been meaning to build a Big Muff. Hmmm...
-Joe Hart

[lars]

Great post, I'll definitely save the information. I've noticed that the input cap on a Big Muff circuit has a great effect on it's sound. Personally I think the typical 1uf or higher caps on the input make it sound too muddy. The combination of components that Kit Rae deciphered from an original triangle knob muff I would agree is the best overall sound:  http://www.kitrae.net/music/Images_Secret_Music_Page/KITS%20V1%2066-11%20SCHEMATIC.jpg

Those big .12uf green film caps do have a particular sweetness to the sound. My favorite Big Muff has to be the Op Amp version though. Since there are so few of them there isn't much information on mods. I did accidentally find a noise gate mod for the Op Amp Muff when building one on a bread board. It makes the pedal dead quiet when not playing and also has a unique side effect of "bit-crushing" the sustain on notes. You can hear an effect like this at the very end of Cherub Rock by the Smashing Pumpkins. The notes start out normal but decay very rapidly and seem to break apart, it sounds very grainy. Once I can document the mod properly I'll start a post.

[CodeMonk]

Not to bring back the dead, but here is something related to Tucksters cap switcher I did.
It set up for those 2 pole 6 position switches you can find at Ratshack.


Thought it may be of interest to those in this thread.

Basic PCB layout. Red and blue are your in/out leads. For instance I used this on a Jordan Bosstone recently, and had it switching the input and output caps.
I'm trying it tonight on a Triangle I built last week.


PCB:


Partially in use: