Queen of Bone 'Swell' when engaging???

[fman7]

Hey (hope this is right place to post this??)

Built a Queen of Bone and is sounding great, but when I engage either side of the pedal the sound swells up to volume, checked suppy, charge pump and IC voltages with DMM and they stay constant when I engage, but the audio swells.
Using MAX1044pump and 4580 opamps.

Can anyone help?

cheers