Why is the mid-scoop so inherent in the Big Muff design?

[south_saturn]

I have had numerous USA and Sovtek Big Muffs plus a Triangle clone that I have recently built as well as my newly accquired Euthymia ICBM and they all, predictably, have a lower amount of mid-range frequencies than I would like. What is it, specifically, about this circuit that leaves us with that all too familiar scoop?

I ask because when using them in a band setting (unless you have a massive boost in volume) they just get loast behind the drums and bass. Are there any well known modifications to add some kind of mic control or maybe to give the Muff a flat EQ?

Thanks.

[Mark Hammer]

If you want to sell a distortion to pro musicians,that's one thing.  If you want to sell millions and millions of distortions to bedroom rock stars, you need to make the bass sound huge and the treble sound sizzling.  You can do that by attenuating the mids. 

And it isn't just the BMP.  The list of distortion pedals with some form of midscoop is very very long.

[Fender56]

Using this free software: http://www.duncanamps.com/tsc/index.html, you can simulate the BMP tone stack. You clearly see the notch in the mid. Change the values until you find something that you like and implement the mods into your pedal!

[russv]

That is a pretty cool program. Is it really as easy as changing C1 to a 10n?

[south_saturn]

Thanks for the responses. I'll give that tonestack calculator a try tomorrow.

[Caferacernoc]

That is a pretty cool program. Is it really as easy as changing C1 to a 10n?

Yes.
R1 to 10k is cool too. Fattens up single coils nicely.

[John Lyons]

Bypass the tone control and you'll get a lot more mids!! Not to mention a lot more level...
Duncan's TSC is great because you can get rid of that mid notch easily by plugging in different cap values.

Take a look at the Big muff, BSIAB2 , Hot Silicon, box of rock and a few others that use the big muff tone stack.
Some of them have a mid notch some do not.

Also takle a look at AMZ above for the Lab Notebook and "presence control" which deals with the
BM tone stack and getting the mids back with a "body" control.

John

[tcobretti]

Since were talking about BMP tonestacks, don't forget about the Wayhuge Swollen Pickle which is a BMP with an even deeper mid-scoop.

[bwanasonic]

There is A TON of info here (archives) about fiddling with the BMP tonestack, and other tips for your *holy grail* big muff.

Kerry M

[brett]

Wait.... before everyone decides they've seen the frquency response of the BMP tone stack. The BMP tonestack *isn't* quite the same as the one shown in Duncan's tonestack calculator.  The architecture is good, but not values.  Specifically, the output impedance of the previous stage is about 15k, and the input impedance of the next stage is only 80k or thereabouts (TSC shows 1k and 1M for these, respectively).  Putting the correct values into the TSC shows bass getting cut less than treble (and much less than the middle of the "scoop").  This fits the common perception of lots of bass in BMPs.

The BMP tone section could have been made much more independent of prior and post stages by usig a 10k linear pot (and changing the other values to fit) instead of a 100k pot.
cheers

[Mark Hammer]

A suggestion....

The BMP tone circuit consists of a 1-pole lowpass, and 1-pole highpass filter, whose outputs are mixed by the tone pot.  Each of those filter sections has one component tied to ground.  If you stuck a resistor between them and ground, there would be less bleedoff.  So, to effectively "bypass" the tone circuit, try sticking a 470k fixed resistor between the ground side of the resistor and cap on each side of the tone pot, and ground.  A SPST toggle can be used to shunt it and restore the tone function.

[Branimir]

I have found reducing the mid scoop in the BM tonestock horrible sounding, but leaving the tonestack as it is in big muff and boosting mids on the amp's tone control helps alot, I know, it's boosting something that's been cut out of the soundspectrum already, but it does work...

Not all pedals are plug'n'play like fuzz face, big muff can sound good with a bit of a knob fiddling on the amp itself...

[Gus]

Look close at one of the big cheese settings.
  Like Brett posted don't neglect the source and load resistance that the control sits in between.

[earthtonesaudio]

This is good also:
http://www.muzique.com/lab/tone3.htm