cascading LPB stages suggestions

[jishnudg]

Hey!
Seen this tried before on this forum,by pinkjimiphoton and Rick Holt, I've been trying to draw out a similar approach, would love suggestions on how to improve this thing.

http://i64.photobucket.com/albums/h169/jishnudg/20141205_120702_zpsf2c0689b.jpg~original

[jishnudg]

The Dual gang pots are cause I ended up with a huge batch of these 10k and 100k stereo pots by mistake and am trying to get rid of them   The sound I'm gunning for is a modern, mid scooped, tight, compressed and focused distortion in higher gain settings, and warmer and more open at lower gain settings. Would a schema like this work to that effect? A few more questions -

1. For the 2 transistors - -all I have is 2N3904s.. should I be biasing them differently?

2. Should the cap values around the first transistor be smaller? (around 0.047uf maybe?)

3. Is the 100k dual gang pot for the notch filter in stage 2 overkill? Would it be better with 10K?

4. is there any way I can make a diode pair interact with the notch control, so the clipping increases with the scoop?

5. Pinkjimiphotos LPB has a diode pair attached to where the "gain" pot is on my schematic - -I still don't get how this would work, would love some inputs on whether adding something similar would improve this.

6. A schematic I saw once on Smallbear Electronics had a modified LPB with diodes in a feedback loop (can't seem to locate that drawing) - - would this help here in any way?

EDIT - jack ormans "muffer" http://www.muzique.com/schem/muff.gif   seems to have it too....is this "soft clipping" ?

[antonis]

Just to make the scheme easy visible..





About soft clipping: It's common practice to consider a clipping stage as "hard" when it's involved straight to the signal path (i.e. between signal and ground) and "soft" when it's in the feedback loop (gain stage)

edit: The biasing point is about 1.6V (if you connect the second BJT to +9V also.. ).. You have a variable gain from 1 to infinity so you can get an assymertrical distortion with a gain over 15 - 20 (depending on you guitar's signal..)

Caps values for first BJT are "generally" OK.. You may reduce their values if you want more bass scooped..

[jishnudg]

Thanks,Antonis! couldn't figure out how to get that image to display here...yes, so I guess it would be 'soft' clipping...but would it make any sense to put it here in the feedback loop of the first 2N3904? if it is followed by hard limiters right after the gain stage...?

[antonis]

I'm no sure about it..

I've seen additional clipping stages but all of the same "kind"..

I don't think that an allready soft clipped signal should have any affect on the hard one...

But there is a quite interesting discussion here: http://www.diystompboxes.com/smfforum/index.php?topic=106650.0