Help with high pass filter switching

[armdnrdy]

Not too long ago, I posted a project for the Maxon AD-900. (4-MN3008 version)

The repeats of this delay sound a bit "dark" so, I had the thought to add a switch to choose between the stock delay, and brighter repeats. A bright switch if you will.

I would like to add the switch instead of making permanent changes to the delay because I see the usefulness of both sounds...both dark and bright.

I tried a daughter board which switched in and out the complete anti-aliasing and reconstruction filter sections equipped with lower value capacitors.
This didn't work. For reasons unknown to me, this changed the bias at the BBD input.

I have a few more things to try but would like to get some advice from those more knowledgeable on the subject of filters before I plot my next move.

My thought is to concentrate my efforts around the area between the wet output of the "level" pot and the summing amplifier/de-emphasis filter at the output.

Reading up on high pass filters, I've found that the combination of C40, (4.7µf) R52, (10K) R54, (10K) and IC1A make up a first-order, non-inverting high pass filter. What I'm not sure about is if this holds true with the de-emphasis filter in the feedback loop of IC1A.

Would adding a "bright switch" be as simple as switching in a lower value capacitor for C40, and possibly a lower value for R52 to make up for loss in signal by changing the bass response of the wet signal?



Here is a link to a PDF which is easier to read:
https://dl.dropboxusercontent.com/u/53299166/DIYstompboxes/AD-900%20MN3008%20version%20schematic.pdf

[armdnrdy]

Okay...

I ended up pulling C40 and soldering a couple of wires to the pads to experiment with different configurations on a breadboard.

When C40 (4.7µf) is replaced with a much smaller value cap, it does cut the bass (muddiness) and lets the higher frequencies pass.

I'll experiment with different values to find something that I feel is good for a "brighter" sounding delay.

Edit: I do hear an apparent volume drop in the wet signal when I connect the smaller cap (bass cut) so, I'll have to experiment with lower values for the weighting resistor (R52) to achieve a good wet/dry ratio.