Feedback Loop Clipper tone/gain Control

[WGTP]

OK, It looks like to me there are 2 commonly used methods

The pot/cap to ground coming off the loop, which rolls off the lows (if the cap is set right) as the gain is increased by reducing the resistance.

The pot/cap in parallel, which (if the cap is set right) rolls off the highs as the gain is increased by raising the resistance.

Is there an advantage of one over the other???

Second, I'm thinking with folks using dual op amp clippers, Chaos, RoseyRay, HMP, Strong Gout, Blues Breaker, etc. the first type could be used to control the lows in the first stage and the second could be used to control highs in the second stage.

Of course you could do both in a single stage if you preferred.  

This would be an easy way to adjust for different guitars and amp without having to re-tune the pedal.  

[cd]

Is there an advantage of one over the other???

Well obviously, if you wanted to cut lows, a low pass filter (cap in the feedback loop) would be useless.  Where it gets sticky is the examples you've cited adjust the frequency response of the clipping stage itself.  What about pre/post clipping?  Cut the highs and lows AFTER clipping (i.e. make the clipping stage all-pass) and it sounds completely different.  Same with before.

Google Baxandall tone controls, high pass and low pass filters, there's a ton of info out there.  You might also want to start with the book "DIY Projects for Guitarists" by Craig Anderton (check your local library) there's a whole chapter there on designing your own preamp which delves into frequency response, another chapter with an EQ/tone control, etc.

[WGTP]

You still may want a tone control of some variety afterwards, but what I'm thinking, it that by varing the gain/tone of the different stages, one higher and one lower, it would produce different flavors of distortion.  A bright stage and a dark stage.  

For the first stage, a 1K resistor and .1uf cap produces a 1600hz roll off and a 10K produces a 160Hz roll off.

For the second stage a 1M pot in the loop and a .001uf cap, the roll off is at 160Hz, but with the pot turned down to 100K, the roll off is 1600Hz.

The gains and roll offs can be changed by the balance of the 2 op amps.

Next is using diodes to ground for the first stage and diodes in the loop for the second, for 2 different types of distortion to throw into the mix.