Abominable Hail Satan Muff LED mode

[Mattallica]

I'm working on a Big Muff build, and I've done a little mod where the D3 and D4 diodes are footswitchable between 1n914 and 5mm red leds. I like the sound I get with both, but it's a subtle difference at best. I've enclosed a photo of the layout for the build by lvLark.

My question is, how in the sam hell is the Abominable Hail Satan getting such a dramatic "boost" in volume just by switching on 2 red leds? Is there something else going on here? There's no way just switching either pair of diodes to leds in a muff build would make it scream like that, is there?

I'd like to achieve the same effect with my build, but so far no dice, just a small difference in tone when switching either pair of diodes to led, though d3 + d4 make the biggest difference (which isn't saying much).

I've included a video clip, watch 1:50 for the led mode engaging: http://youtu.be/adaRQb6_GMA

[EBRAddict]

My guess is that the resistor value leading into the gain/clipping stage from the prior stage is being reduced with the same switch. That would have the effect of increasing the gain of that stage.

[Mattallica]

Gotcha, any idea how to implement that resistor value decrease on a dpdt footswitch?  I'm using one with the 1n914s on one end and the leds on the opposite end, with leads from the middle terminals going to the rows where d3 and d4 are in the circuit.

[Lubdar]

Is the hail satan just switching out the diodes in one stage or both? there are lots of combination ideas to get that "boost" with clipping alteration you're interested in.
As you probably know the diodes have an impact on the clipping characteristic. and the Feedback resistor in the gain stage is associated with more or less saturation/"gainyness".

What EBRAddict mentioned would work, either that or increase the feedback resistor in the same clipping stage as well to 1M for more gain. Or toggle off the diodes in the first stage and set the second stage to LEDs (really loud..)

[Mattallica]

Thanks for the suggestions guys! I've achieved the result I was looking for by putting a pair of 5mm green waterclear leds in stage 1 for D1/D2, and piping out D3/D4 to the dpdt switch with 2 1n914 on one end and 2 5mm waterclear reds on the other.

It's a pretty dramatic increase when kicking on the reds with the switch, pretty dang close to the hail satan. Overall, this is a really cool build with this mod.

Note: I tried the 3-way mid switch with the little green radioshack grasshopper caps and they are really "meh" overall, so tomorrow I'm going to replace them with a couple mylar film box caps of the same value and see if that's a bigger difference in the midrange content when flipping the switch. I'll report back!

Thanks again doods!

[Mattallica]

Note also that with the greens in first stage, it's *almost* like having no diodes at all, but it's slighly more "civilized" if that makes sense. Like it doesn't sputter and splatter all-out on the high notes like a fuzz factory. It's like a medium between no diodes and diodes, to my ears anyway. I probably sound like a dirty layman here, but that's the best I can explain haha!

I ended up putting sockets in for d1/d2 and trying out a bunch of stuff.

[Lubdar]

That's great news, glad to hear you got it worked out.

[EBRAddict]

This may help, looks like the diode switching is between 2x 1N4148/1N914 and 2 LED



Here's the PCB, I think the 4558 is a switchable input buffer from one of the toggles.

[Mattallica]

Awesome! Thanks for the pics on this. Project is turning out pretty cool. It's a *Much* more drastic difference between led/regular diode clipping on a super-clean amp setting than it is a slightly dirty amp setting, but it's still pretty cool. I'm thinking of trying 3 1n914 set up for asymmetrical clipping on the diode side of the dpdt to see how that pairs up with the red leds. Still digging on the pair of 5mm waterclear ultra bright green leds in stage 1/d1+d2 of muff circuit as well.

I think my next project after this will be a regular muff with leds in all four diode spots, with all of them piped out to the front panel of the enclosure in an aesthetically pleasing way, so that all 4 light up as you play and it compliments some cool art. 

Matt Dunn of Dunn effects did a "Thanos" pedal where it had a picture of him on the front, wearing the infinity rings and there was a different color led for each ring, I thought that was killer! Maybe something like that, but I digress...

[turkeypills]

This may be a noob question but won't the LEDs only light up is they are grounded? For some reason, my Muff builds with LED clipping, the LEDs don't light up. They do light up in my rat builds.