Effect of PT2399 anti-latchup circuit

[Pimpom]

I'm not exactly new to electronics but this is my first foray into echo/reverb.  As a first experiment, I built a simple reverb unit based on the PT2399 and it works as expected - except that, when the unit is switched off while the amplifier is still on, there's a whooshing decaying squeal as the unit powers down (I used a separate regulated supply to test the reverb unit). This doesn't happen if the unit and the amp are turned off at the same time.

The delay control pot has a fixed 2.2k resistor in series to avoid latch-up, but then the minimum delay is around 55 msec. This was also expected. Further reduction of the delay time would need an anti-latchup circuit and I've designed one using a MOSFET.

I could just go ahead and build another unit that includes the anti-latchup circuit but I was wondering if I could save time by making use of other people's experience. Does the PT2399 produce some extraneous sound when it comes on with the anti-latchup circuit?

[Pimpom]

Somehow I failed to notice that there's a "Building your own stompbox" section (but saw the Digital & DSP section just below it). Could the mods please move this thread there or is it OK if I just repost it?

[nejir]

During the power-on of the circuit, if the delay resistance from pin 6 to ground is less than 2kΩ then the PT2399 may latch-up, which will make the chip to crash and stop. ... After the first 400ms, the pin6 resistance to ground can go as low as needed.