Big Muff tone section: Researching the mid scoop and excess bass.

[brett]

Hi
Using Duncan's Tone Stack Calculator, I get these results for the standard Big Muff.



With results like these, it's not surprising that many people feel there's too much bass in it.  But it is surprising that people blame the large coupling caps (1uF) rather than the tone section, which is obviously the place where the treble is being lost. 

If you turn up the tone control, it comes into balance, and there's a scoop, but it's very small, and at about 500Hz rather than the 1kHz that is often described:



But here's a muff tone section, with only two resistors changed, that gives that looks much better.  The notch is deeper and its frequency is quite responsive to the tone control setting.  (I haven't built this in a muff yet, but it worked very well in the Whisker Biscuit).



Why the myths about BMP bass and mid-scoop?  The defaults for the BMP tone section in the TSC indicate plenty of treble and a definate mid scoop.  But the default values for source and load impedances (1k, 1M) are quite different to the actual values (23k, 100k).  The actual values for those parameters make large differences.  These differences  seem to have been overlooked in the threads that I found by searching through in the forum.

Comments?

[Meanderthal]

    *  Triangle version: R1=33k, C1=4n, R2=33k, C2=10n;
    * Ramshead version: R1=33k, C1=4n, R2=22k, C2=10n;
    * 1975 version: R1=39k, C1=4n, R2 = 22k, C2=10n;
    * 1977 opamp version (1): R1=5.6k, C1=100n, R2=1.2k, C2=120n;
    * 1977 opamp version (2): R1=8.2k, C1=100n, R2=1.2k, C2=120n;
    * Green Russian version: R1=20k, C1=3.9n, R2=22k, C2=10n;
    * Late model: R1=39k, C1=4n, R2=100k, C2=10n
    * Reissue version: R1=22k, C1=3.9n, R2=22k, C2=10n;
    * Little Big Muff version = reissue version.


By "standard Big Muff" you are referring to the black sovtek version?

[Meanderthal]

 I got rid of the mud by changing the coupling caps to .1uf. And I play bass. The mud's no myth. And it ain't the tonestack that makes it get muddy, that's what causes the notched mids. Which might cause you to "drop out" of the mix in a band situation.

[Meanderthal]

Flat mids: R1=33k, C1=5.6n, R2=33k, C2=5.6n
Swollen Pickle (way huge mid notch hehe): R1=33k, C1=3.3n, R2 = 22k, C2=47n

These are only different tonestack values. And then there's the rest of the circuit... There is no Standard Big Muff. And each and every one I've ever heard, even the same year, model, version, or what have you, sounds different. Now that's what I call "loose tolerance"!

[brett]

Hi
The results for the most popular versions that you mention are:
Triangle = 3dB scoop at 1k, 10kHz=6dB less than 100Hz.  ie weak scoop and a moderate treble cut.
Ramshead = same scoop, bit more treble cut.
Breen Russian = No scoop, 10kHz = 9dB less than 100Hz ie large treble cut.
Late model = what I called the standard = no scoop, 10kHz = 5dB less than 100 Hz.  ie no scoop and moderate treble cut
Re-issue = small scoop, 10kHz = 8dB less than 100Hz.  ie large treble cut

So it doesn't matter too much which tone section is in your BMP.  They all have little or no scoop and knock several dB off the treble.   For the purposes here, none of them have a balance between bass and treble.

Those 0.1uF caps will roll off the bass for sure, and give a rough and ready result.  BUT it probbably doesn't make much sense to roll off bass with filters in the gain sections to "cover" a tone section that boosts the bass.

There seems to be consensus that a decent scoop (5dB) and no loss of treble would be good (ie flat from 3kHz to 15kHz, and at the same level as the bass).  As I pointed out above, that can be done very easily by making R1 = 100k (39k in late or "standard" models) and R2 = 33k (100k in late or "standard" models).

PS Those "flat mids" values take the notch out, but treble is still down on the bass.  The Swollen Pickle results are amazing.  The notch is very deep, and wide on the bassside.

[Meanderthal]

 Years ago I knew a guy who had one called the "little big muff", not to be confused with the new one in the hammond enclosure. This one had one knob and one switch. I think the knob was volume, no "sustain" control, and the switch said "tone" and was apparently a mid notch.
Sounds sweet, huh? Nope. It was easily the worst "big muff" I ever heard. Absolutely drowning in mud. That's why I contend that the mud ain't from the tonestack- I've heard it without, both in this case, and by deliberately bypassing mine.
It IS, however, a different sound without it. Even more intense...
BTW, I built a whisker biscuit about a year ago... noisy as hell, but a VERY impressive character to the sound! They said their goal was to create an alternative to the big muff, and they very much achieved that goal! Mud isn't a problem in mine...
 

[Elektrojänis]

BUT it probbably doesn't make much sense to roll off bass with filters in the gain sections to "cover" a tone section that boosts the bass.

Yes it does.

In distortion circuits, it matters very much where the tone shaping is. Usually it helps to cut bass before distorting the signal to make it sound less muddy. If needed, you can boost bass after distortion and it will not make it more muddy (as long as you don't boost it too much).

So, modding the input caps and modding the tone section are two different mods that will produce two different sounds.

In marketting terms the one with the smaller input cap would probably be called distortion, while the one with bigger input caps would be called fuzz.

[MartyMart]

Absolutely, removing bass "mud" pre-distortion is almost always a "good" thing !
My recent BM has a mix of 100n/1uf caps, I tried to keep the distortion thinner
then get some bass back in, worked great , it's my best BM sound yet
( Tone stack was triangle version 33k/3.9n/33k/10n )
I did find my original triangle build to be too thin will all 100n caps though .

MM.

[brett]

Hi
What are the popular opinions about the bass-treble balance of various BMPs built with the 1uF caps out and the 0.1uF caps in?  Are they good?

I guess I could build and compare a couple of BMPs: one with flat gain/distortion sections and a scooped tone section, and the other with the 0.1uF caps and the bass-boost, scoopless tone section.

One reason why I'm being quite sceptical about this bass cut then bass boost thing is because there's no equivalent in excellent distortion/fuzz circuits like the Bosstone, MXR D+, Fuzzrite, MFZ-1, tube sound fuzz, easydrive, fuzzface, bazz fuss...

cheers

[Elektrojänis]

One reason why I'm being quite sceptical about this bass cut then bass boost thing is because there's no equivalent in excellent distortion/fuzz circuits like the Bosstone, MXR D+, Fuzzrite, MFZ-1, tube sound fuzz, easydrive, fuzzface, bazz fuss...

It all depends what you are after... Usually the more bass you feed the clipping part of the circuit, the fuzzier the sound.

Many circuits cut bass before the distortion but usually the bass is not boosted afterwards... Usually tho post bass boost is not even needed (at least with guitars).

Pedals that cut bass before distortion: Tube Screamer, Rat and most things that say "overdrive" on them.

[Mark Hammer]

Years ago I knew a guy who had one called the "little big muff", not to be confused with the new one in the hammond enclosure. This one had one knob and one switch. I think the knob was volume, no "sustain" control, and the switch said "tone" and was apparently a mid notch.
Sounds sweet, huh? Nope. It was easily the worst "big muff" I ever heard. Absolutely drowning in mud. That's why I contend that the mud ain't from the tonestack- I've heard it without, both in this case, and by deliberately bypassing mine.
It IS, however, a different sound without it. Even more intense...
BTW, I built a whisker biscuit about a year ago... noisy as hell, but a VERY impressive character to the sound! They said their goal was to create an alternative to the big muff, and they very much achieved that goal! Mud isn't a problem in mine...

The "Little Big Muff" was essentially a BIg Muff, except that:
1) the Sustain setting was preset rather than pot-governed.
2) The 100k Tone control was replaced with a 100k fixed resistor, and the switch selected from one end or the other of the 100k resistor.  Essentially, it mimicked turning the Tone control all the way to one extreme or the other.  As Alfred E. Neuman would say, "Blecch!"

[Elektrojänis]

One thing that might be cool experiment is a pedal that has one big muff tone control before the clipping part an one after it. It would be nice if those controls had somewhat balanced responce when centered. Different center frequencies could be tried too ofcource.

[Mark Hammer]

The contour control on the Marshall Shredmaster, and some of their Valvestate amps, looks like a really flexible control and worth exploring,.  I wrote up a little bit about it here: http://www.diystompboxes.com/smfforum/index.php?topic=31514.0

[Meanderthal]

 Thanks for straightening that out for me Mark! Well I was certainly wrong about the LBM. It sounds horrible BECAUSE of the "tonestack". Not in spite of an absence of one. I had forgotten how shrill the non- muddy switch setting was ! Instant headache!
You know, the more I think about it, the more attempting to fix the sludge through tonestack manipulation intrigues me... might lead to a fix-all solution...
That's the wierd thing about BMPs- some sound great with the .1uf caps and some with the 1.0uf. I've owned a few and opened up a few more... they're ALL different.
And then some just sound ... frighteningly WRONG and need fixin'.