Big Muff Feedback Mod

[cnspedalbuilder]

Hi, I've built a GPCB Big Muff circuit and want to box it with a momentary feedback switch. I was thinking about doing the oft described mod from one of Brian Wampler's posts that's also on Kit Rae's site:

"Connect the emitter of Q3 with the emitter of Q2 through a switch (so you can turn the loop off). The sustain will be on full when this mod is engaged"

The only thing is that I've soldered in the transistors and I'm not keen to desolder them. Is there any reason I can't just run the circuit output back to the input, as opposed to linking the two transistors?

[cnspedalbuilder]

Maybe my last message was too verbose. Here is the quick question:
For the big muff feedback mod, do I have to link the two transistors, or is it fine to just run the circuit output back to the circuit input?

[Derringer]

I'm not really following the logic of the mod, connecting the emitters of Q2 and Q3.

Those emitters usually are connected to ground through a 100 ohm resistor. I don't see how connecting them together, so that they share a resistor would do anything noticeably different, and really don't see how that will affect the level of sustain.

Can you post a link to where the exact mod was given?

[cnspedalbuilder]

Yes, I didn't quite get it either. Here's a link on Kit Rae's site:
http://www.kitrae.net/music/Big_Muff_Mods_and_Tweaks_Page.html

Coda Effects also has a page and here is their excerpt from Kit's site, along with his own comments:

Feedback mod

This mod is also not for anyone. It will give the Muff a weird drone note that will interact with the notes played resulting in octaves (up and down), nintendo sounds or a huge MUSH. Can sound quite nice and interesting!!!!! The mod is done with a feedback loop: connecting two points together and letting signal flow back. I found two of these loops in my Muff (note: more can be there; try for yourself!)
Connect the emitter of Q3 with the emitter of Q2 through a switch (so you can turn the loop off). The sustain will be on full when this mod is engaged.
Connect the collector of Q3 with the collector of Q1 through a switch. The sustain now can be varied by the sustain knob.
Great addition: add a 1M potmeter in the loop (wired as a variable resistor) or, even better!!, a LDR (light dependent resistor). With the latter, you can control the amount of feedback with the light on stage / with your foot shading the LDR from the light. Cool!

Note from Coda effects: this is really cool, but I will suggest to use a momentary footswitch. If not, you can be quickly bored with the noisy issues that will rise from this mod. However, from times to times (beginning of a song), it is a killer mod to use!

[PRR]

> I'm not keen to desolder them.

So? Tack-solder a wire to each emitter's solder-blob, and run them to a switch.

[Plexi]

I was to suggest to link Q1 collector to Q2 collector. But now I see you mentioned in your last post.
The emiters aren't direct to groud: have resistors to stabilize the gain.
As the good sir PRR says: just add a switch there.

[cnspedalbuilder]

Thanks I can certainly follow the suggested mod, I was really asking whether there's anything wrong with just running the circuit output to the momentary switch then to the input. Is there any reason not to do that?

[ashcat_lt]

Thanks I can certainly follow the suggested mod, I was really asking whether there's anything wrong with just running the circuit output to the momentary switch then to the input. Is there any reason not to do that?

Well, if the guitar is plugged into the input, and you connect that to the low impedance output, you'll lose quite a lot of treble.  If you literally just connect the two jacks, the volume pot will have some effect on just how much treble you lose, but it's kinda gonna be tone suck no matter what.

Of course, it'll also act as a sort of clean blend since if the output can to the input, the input can also get to the output.

I'm not real clear on how the suggested mod works.  Can anybody shed a little light there?

[PRR]

> asking whether there's anything wrong with just running the circuit output to the momentary switch then to the input.

NO! You would reverse the polarity of the whole Earth, it would flip-over, and the Aussies would be in the North!

Oh, OK, just do it. (We will hang on tight.) It is not clear WHAT that will do. I doubt it can be "same as" the documented mod (Note the doc says "This mod is also not for anyone.") . As Ash says, it will interact with the source in unexpected ways. It might get Very Loud, or just go dead. It probably won't eat your cat.

[PRR]

> how the suggested mod works

I'm not "clear" either. But look at Q2 Q3 with emitters connected together. Now look at an emitter-coupled multivibrator. There's positive feedback. There's filtering so whatever happens may happen mid audio band. I don't know if it will or won't oscillate on its own. A free-run oscillator with an external signal fed in will tend to shift frequency and amplitude in tricky ways. Looks horrible to me, but I guess that is why he likes it.

[cnspedalbuilder]

emitter-coupled multivibrator

I'm afraid if I look that up, some strange stuff will show up in my search history 

[bluebunny]

emitter-coupled multivibrator

I'm afraid if I look that up, some strange stuff will show up in my search history 

You've been googling "muff".  The thought police are already across the street in that unmarked car...   

[graemestrat]

I'd like to be in the North for awhile.
You do get tired of everything being upside down...........

[duck_arse]

NO! You would reverse the polarity of the whole Earth, it would flip-over, and the Aussies would be in the North!

I'd be prepared to put up with the warmer weather too. also, there is two cats here, I don't mind if they get eaten.

[Plexi]

emitter-coupled multivibrator

I'm afraid if I look that up, some strange stuff will show up in my search history 

You've been googling "muff".  The thought police are already across the street in that unmarked car...   

Be carefull of autocorrect: "muff", not "snuff"

[pinkjimiphoton]

emitter-coupled multivibrator

I'm afraid if I look that up, some strange stuff will show up in my search history 

You've been googling "muff".  The thought police are already across the street in that unmarked car...   

Be carefull of autocorrect: "muff", not "snuff"

hahah plexi, we call that hamburger syndrome.

if ya say humbucker on a lot of cell phone speech to text functions, it will change it to hamburger.

its like, MAGICK or something

[antonis]

So guys, is everything Ok with the momentary switch..??

For a moment, my sink started to drain water CCW...

[duck_arse]

So guys, is everything Ok with the momentary switch..??

For a moment, my sink started to drain water CCW...

I think you mean ".... my sink started to drain water from lug 3". [or something.]

[cnspedalbuilder]

For the archives: I tried the feedback mod as suggested in the pages linked above, and it works. I was hoping for/expecting a squeal that changes pitch uncontrollably and unpredictably. Instead, you get a thick nintendo-ish hum though it is modulated a bit by playing something. Initially I thought I'd not use it, but I've been playing around with it and on a momentary switch, you can do some interesting stuff. Also, the momentary switch I'm using seems to be kind of dodgey (it disengages if you step hard all the way to the bottom but is engaged with soft pressure) and that has allowed me to get interesting sounds.

I've got it boxed up with a switchable Green Ringer, and the ringer definitely increases the weirdness of the feedback.

[DeusM]

I hope it sounds good for you! 

I tryied and I was also expecting some weird out of this planet sounds but instead it felt more gainy and it had a high pitch note when I wanst playing but I dind't get that octave up - octave down sown described. Maybe it's beacuse I @#$%ed up the circuit  Seriously, I'be encountered a page describing some in depth things about the circuit and there are some things that I wasnt supposed to do but hey, nobody tolds me what the hell to do 
Anyway, you should try also adding a resistor in between the conection, it gives you diferent pitches but you can change that by using the feedback knob. Also there are other loops, just mess arround shorting those trans sisters