BigMuffPi diode boost

[Brymus]

I breaded a BMP a couple of weeks ago>It sounded awful...Let it sit while I been sick,
Finally got back to it this week,(ended up pretty close to the GGG tuned version after alot of trial and error)and got it sounding good,anyway...
I found that switching between two different sets of diodes at Q3 can give several dB of boost,if you choose the right ones.
Going from 1n5711s to 1n4148s gives a nice boost that would be useful for leads,easy enough to wire to a DPDT footswitch.
red LEDs were the loudest,just as loud as none being there,but better sounding than none >YMMV on that.
1N34As were the quietest I tried yet. Try some different ones for yourself and see.
Anyway sorry if this mod is common knowledge,just though I'd share since its pretty cool

EDIT I just tried on my 18watt Marshall,the difference between 5711s and 4148s isnt as pronounced as it was on my little Crate.
For big amps 4148s and 1n34s should be good or the 4148s and Red LEDs ,1n34s and LEDs will have a big boost diffrence.

[John Lyons]

The more voltage the diodes pass the more sound cones out the other end.
Germanium is about .3v or so.
Silicon about .6v
LED 1v+
Putting diodes in series raises the voltage and the volume out.

What's happening is the the diodes are limiting how much
signal passes through. The signal is "bounded" creating a squared
off signal. Amplify this and clip (off the top of the signal peaks) and you
get a mega square wave yet somewhat smooth dues to the filtering of the
470pf caps and caps in series with the diodes which set the frequencies
that the diodes clip.
Taking out the first set of diodes (as in the Jumbo tone bender) gives you
less fuzz but a big sound...think bass fuzz!!

You can also use different diodes per pair, One silicon and one Germanium
etc to create more asymmetrical clipping.

[Brymus]

Thanks John I need to learn how and why different diodes sound,different,thats some good info to start with.
I havent tried mixing the diode types yet will try tonight.
I did notice (when playing on my 18watt,it was so noticable on my practice amp)that when using the 4148s (Q3)I got that "noise" you have in your 22/7 build ?
However switching to the Ge 1n34As the noise went away,not just due to lower volume either as I cranked it and even at way louder levels there was still almost no noise with the Ge's.
So I tried the usual mods to remove the "noise" to no avail,when using 4148s at Q3 I get some disturbing "noise" just like your clip of the 22/7 you built.
Did you ever remedy that ?
Do you have any explaination why the noise is only with the higher forward V (I think I'm understanding this part right) diodes ?
I was thinking maybe the Q is to blame more than the diodes but IDK...
And have you tried Ge's in your 22/7 instead of the Si ones ?  This might be a fix for that BMP clone

[nbabmf]

I really only use 1N4148/914, 1N34a, and LED's.  Only lately have I begun to experiment with other Ge diodes that I have found surplus.  I'm curious about these 1N5711 diodes.  What are they?

[Brymus]

I really only use 1N4148/914, 1N34a, and LED's.  Only lately have I begun to experiment with other Ge diodes that I have found surplus.  I'm curious about these 1N5711 diodes.  What are they?

Here you go http://www.st.com/stonline/books/pdf/docs/3238.pdf
Mouser shows a pic of bronze/4148 looking diode,the ones I got from them are blue with black stripe,twice they came that way.
The 1N5711 sounds really nice in TS clones too.
I tried again today,I was looking at the wires wrong yesterday (trying alot of diodes) and switching between the 5711 and 4148 gives a really nice boost in volume ,without the treble mismatch of going from Ge to 4148.
Bryan

[John Lyons]

The Ge diodes make the pedal quieter and therefore less noise.
More noise with the 1N4148 is because there is more signal getting
past that stage. The aren't adding noise, just letting more signal through
to the next stage.

I didn't resolve my noise issue in th 22/7