No no, I wasn't suggesting that.
I don't have one of these built at the moment to try this myself, but if you're feeling experimental....
Try each one of these modifications one at a time, test it after each one and see if there is any improvement.
- Remove R3 (100K)
- Disconnect lug 3 of the Depth pot, reconnect it using a 1uF electrolytic cap. (Positive lead to the Pad, Negative lead to Lug 3 of the pot)
- Increase the value of R7 (currently 470R) to 1K - 2K2.
- Increase the value of R6 (currently 39R) to 100R
Let me know if any of this helps.