Making a Big Muff clone with switch to toggle a different distortion sound.

[davidjnichols]

Hey guys.  I want to make a Big Muff clone.  I'm thinking the Green Russian version.  I would, however, like to add a mod and I'm not sure exactly how to do it.  I'd like to add an SPDT switch to toggle between the regular muff sound and a more distortion/less fuzz sound (maybe like BSIAB).  I'm not sure exactly how to achieve that.  Here's my idea and schematic I'm referencing:

http://www.pisotones.com/BigMuffPi/psst/schm-green.jpeg

The fuzz comes from the two pairs of diodes, yes?  Could I install a switch that would bypass the first pair of diodes and instead run it through a pair of LEDs or something else?  Anyone else modded this thing to sound less fuzzy and more like a distortion?

[davidjnichols]

I'm still new to all of this and have a hard time identifying the different sections of a schematic (ie which section produces the fuzz, which caps change bass response, etc).  Is there an easy component swap that can be done to make it more distortiony and less fuzzy?  Kind of like how you can change the diode configuration in a Tube Screamer for a different tone.

[LucifersTrip]

Before you do too much extra work, check out the numerous mods talked about in this forum...for example, daryl took it pretty far...

http://www.diystompboxes.com/smfforum/index.php?topic=99616.0

good luck

[Earthscum]

I use mine for Bass. I have a switch that just lifts the first set of diodes completely out. At higher gain settings, you can hear a really nice combination of transistor clipping and diode clipping. Lot less "fuzz" sounding, lots of bassy thickness and more "distortion" sounding. I've been playing with the diodes out and have considered just lifting them permanently and using the switch to lift the second set so it's just full-out transistor saturation.

[pinkjimiphoton]

i like to take a 3pdt toggle, on/off/on and use that with 7 ge 1n34's on one side, and 3 in914's or green led's on the other wired as diode clippers, and i prefer that in the second clipper.
that way, i have ge clipping and more of a classic fuzz sound, or the diode/transistor sound without the clipper in the middle, and then asymetrical si clipping in position 3, really brings it to life. you can use the extra poles to use a multicolor led to change colors if ya want to even. if you do that for each clipper, you can have an insanely versatile muff really quickly, and that's before any cap or resistor mods..

[kodiakklub]

the best explanation of a BMP ive ever seen:

[davidjnichols]

Wow, you guys are totally awesome!  Thanks so much.  The circuit guide is incredibly helpful.  Also that multi-muff thread is awesome.  I'll let you know how the build goes. 

[davidjnichols]

I think I'll install a diode-lift switch just for the first clipping stage.  Anyone have any good ideas on how to add a pot to control mids?  Or maybe I could use a switch like Daryl did to change the values of the two caps/resistors in the tone section to change mids.  I'd like it to be a little more variable than a simple boost/cut mid switch.  Have any of you tried something like that?

Here's what Daryl had to say about it.  Could I maybe install a pot for one of the resistors?  Hmmmm

"Mids Mod (or a version of it anyway)
This basically involves changing the values of two caps and two resistors found in the tone stack section of the circuit.
The stock circuit has a mid cut, but this mod lets you switch between Cut Mids, Flat Mids and a Mid Hump.

Since I already have the resistors on one of the rotary switches I've added I just need to put the caps on a switch.

Here Is what I decided on:

C10 - C11
0.0039uF - 0.01uF =  Scooped Mids
0.0068uF - 0.0068uF = Flat Mids
0.047uF - 0.0068uF = Mid Hump

I've seen some people just make both Caps 0.01uF and both resistors 39k for the Flat mids. But after playing with 'Tone Stack Calculator' program on the Duncan Amps website I decided to make them both 0.0068uF instead. (and because I always wondered what i'b be able to use those for)"

[Jazznoise]

I know the Volts knob on the Germanium 4 muff is a voltage starve, but what's the bias knob? How can you alter the bias without overtly affecting gain in a series feedback stage like in a BMP? Surely you'd have to have an additional pot feeding DC in or adjust the input stage? Or maybe you could swap R23 for a pot and make C5 bigger to compensate for the additional attenuation.

I really need to breadboard this out over the summer. I like my Big Muff w/ Tone Wicker for the Tone Bypass (not so much the high shelf). But there's so many more options than that!

[Scruffie]

I know the Volts knob on the Germanium 4 muff is a voltage starve, but what's the bias knob? How can you alter the bias without overtly affecting gain in a series feedback stage like in a BMP? Surely you'd have to have an additional pot feeding DC in or adjust the input stage? Or maybe you could swap R23 for a pot and make C5 bigger to compensate for the additional attenuation.

I really need to breadboard this out over the summer. I like my Big Muff w/ Tone Wicker for the Tone Bypass (not so much the high shelf). But there's so many more options than that!

The germanium 4 shares basically nothing in common with the big muff design, just uses the name, much like the metal muff.

[nocentelli]

You can do a bias knob with a dual 50k pot set up for two variable resistors in series with two 6K8 fixed resistors instead of the two collector resistors (usually 12k?). This gives you a lower gain clipp ing sound, right up to insane levels of filth - You might like it.

[Mark Hammer]

The basic difference between the Big Muff and the Sola Jumbo Tonebender is that the Sola uses clipping diodes on the 3rd transistor stage only, while the BMP uses clipping diodes on the 2nd and 3rd transistor stages.  You can hear an example of the Jumbo (or at least a member's clone thereof) here: http://www.youtube.com/watch?v=Hoy89AUSvv4

Convertig between the BMP and Sola is as simple as using a SPST toggle to lift and reconnect the clipping diodes (and their accompanying cap) in the 2nd transistor stage.

[Jazznoise]

The germanium 4 shares basically nothing in common with the big muff design, just uses the name, much like the metal muff.

If you've a schematic to verify this, I'd be extremely pleased to see it.

You can do a bias knob with a dual 50k pot set up for two variable resistors in series with two 6K8 fixed resistors instead of the two collector resistors (usually 12k?). This gives you a lower gain clipp ing sound, right up to insane levels of filth - You might like it.

I was wondering would this route inevitably involve a dual gang, but nonetheless thanks for the interesting thought. Might be worth an experiment!

[Scruffie]

The germanium 4 shares basically nothing in common with the big muff design, just uses the name, much like the metal muff.

If you've a schematic to verify this, I'd be extremely pleased to see it.

Pop over to 'the other site' someone traced one.

Interesting design, but the topology is completely different, Op-Amps & Germanium Transistors, don't even think there's any clipping diodes from memory.

[Jazznoise]

It's an interesting topology, alright. The sounds I've heard from it are fairly Muff-y to me.

In the overdrive section the Bias knob clearly seems to determine the voltage feed to the base of the two transistors, in the distortion section it seems to form part of a divider between the inverted signal being fed to either the output of the TL072 or the Darlington pair. Gain set to 0 ohms gives you unity at the Op Amp output, 100K is max gain. Bias is effected by this, and with both set to 0 the Base-Collector voltage should be near 0, and higher as both the Gain and Bias knobs rise in value.

Or at least that's what it looks like to my untrained eyes. At any rate, I think the Bias knob now makes more sense to me. Thanks!

[davidjnichols]

I got the pedal built with the flat-mids mod in the tone section.  I installed a switch to bypass the first set of diodes&cap but I think I wired it wrong and can't figure out how to do it.  Using this schematic as a reference, I installed an SPDT before C6 with one side wired per schematic and the other side open.  Looks like this only lifts the cap and not the diodes.  When I switch it, there's a drop in low end but no change in distortion/fuzz at all.  Do I need to install the SPDT in front of the diodes on the right side?  Would that lift the diodes and the cap?  This is all still fairly new to me, so please excuse my newbish question.

http://www.kitrae.net/music/Images_Secret_Music_Page/BIG%20MUFF%20CIRCUIT%20GUIDEsm.jpg

[davidjnichols]

I got the pedal built with the flat-mids mod in the tone section.  I installed a switch to bypass the first set of diodes&cap but I think I wired it wrong and can't figure out how to do it.  Using this schematic as a reference, I installed an SPDT before C6 with one side wired per schematic and the other side open.  Looks like this only lifts the cap and not the diodes.  When I switch it, there's a drop in low end but no change in distortion/fuzz at all.  Do I need to install the SPDT in front of the diodes on the right side?  Would that lift the diodes and the cap?  This is all still fairly new to me, so please excuse my newbish question.

http://www.kitrae.net/music/Images_Secret_Music_Page/BIG%20MUFF%20CIRCUIT%20GUIDEsm.jpg

Actually I think I figured it out.  I 'll just use a DPDT to make it easier.

[davidjnichols]

I got the pedal built with the flat-mids mod in the tone section.  I installed a switch to bypass the first set of diodes&cap but I think I wired it wrong and can't figure out how to do it.  Using this schematic as a reference, I installed an SPDT before C6 with one side wired per schematic and the other side open.  Looks like this only lifts the cap and not the diodes.  When I switch it, there's a drop in low end but no change in distortion/fuzz at all.  Do I need to install the SPDT in front of the diodes on the right side?  Would that lift the diodes and the cap?  This is all still fairly new to me, so please excuse my newbish question.

http://www.kitrae.net/music/Images_Secret_Music_Page/BIG%20MUFF%20CIRCUIT%20GUIDEsm.jpg

Actually I think I figured it out.  I 'll just use a DPDT to make it easier.

Well now one side of the switch cuts the output to almost nothing, while the other side sounds similar to the pedal stock but just not as good.  A little flappy low end and not as smooth.  Could someone who has wired a diode lift switch draw for me a little MS Paint diagram of how and where they wired it?  I would be eternally grateful! 

[nocentelli]

[davidjnichols]

Nocentelli, thank you so much! You are awesome! I had the switch on the other side. I'll do that tonight and update with how it sounds.