Designing a discrete op amp feedback loop clipper w/ diode compression

Started by aab0mb, September 22, 2013, 09:08:44 PM

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aab0mb

I've been reading up on the BD-2 :

BD-2 schematic: http://www.freeinfosociety.com/electronics/schemview.php?id=116

http://www.diystompboxes.com/smfforum/index.php?topic=8258.0

http://www.diystompboxes.com/smfforum/index.php?topic=90098.0

http://www.diystompboxes.com/smfforum/index.php?topic=7640.0

http://www.diystompboxes.com/smfforum/index.php?topic=10580.0

It seems as though a few of the vets have broken down the basic topology pretty well. I basically get the discrete op amp set up. I've previously moved the clipping in a BD-2 to the feedback loop of the first op amp.  This is addition to the other common mods made the pedal a really gainy squishy compressed feeling overdrive but the voicing really maintained that full range thing the bd-2 has going for it.  The feedback loop clippers helped to tame some of the harsh highs as well.  So as i'm mourning the loss (stolen) of my sweetly modded bd-2 and contemplating another bd-2 hotrod, i got to thinking "what else can be done to this beast?". 

The common mods are typical coupling cap voicing stuff, clipper variations etc. BUT! 
1)The three band tone stack is just sitting there waiting for pots to replace the resistors. (rehouse is an option if the results seems promising)   
2)The other thing that's been mentioned is reversing the dual gang gain pot on one side so the gains in the stages are adjusted inversely with the knob turn.  Seemed like a cool idea. How else can that dual gang be played with?
3) possibly implementing diode compression in a discrete op amp http://www.diystompboxes.com/analogalchemy/sch/diodeopamp.html
4)feedback loop clippers in one or both op amps and clippers to ground (all possibilities switchable) could really open up a lot of different sounds
5)How are the op amps tuned with the intention of voicing and breakup within the op amp itself?

I'm just seeing all kinds of possibilities with this pedal and or basic three stage circuit block (op amp>eq>op amp) and i'm thinking on the page here. Has anything like this been done? Maybe i missed it if something like i'm talking about is already out there...

I really did like the feedback loop clippers and the voicing of the pedal I had modded before.  It seemed to step outside the typical voicing of most overdrive pedals i've played yet it still had that lovely compression i've grown fond of.  Might as well try to take it up a notch since I have to do it all over again, eh?

I'd like to hear some thoughts or ideas for everyone since i've yet to start the project and i'm in the planning phase right now.