Jeff Rowland Model 2: need help troubleshooting standy noise

I recently acquired a Jeff Rowland Model 2 amplifier for my main system. It sounds fantastic and is a great match with my speakers (KEF R107). Overall, I’m thrilled with its performance.

One issue I’m having is that the amp will send a "hiss" signal down the right channel...only when the amp is off/stand-by mode. When, it’s powered up, there’s no noise. The noise "sssssshhhhhhhhh" will start loud and fade to quiet, then start again a few seconds later (like waves crashing on the beach). This doesn’t happen right after power down, it’s usually the next day (8-12 hours in "off/standby" position). It’s only the right channel and my first thought is a capacitor slowly discharging.

The switch design in this amp is not a hard on/off like say a SS Conrad Johnson amp. It’s a soft push button affair so I don’t think "off" is really off. Some might suggest to just leave it on 24/7, but I’ve never been a fan of this idea. I could auto cut the power at the plug via relay my Belkin Pure AV PF60, but JRDG states in the manual to only use the on/off switch.

I am considering having a professional look into it, but wanted to see if the Audiogon community could help narrow down the search. Thanks for any assistance.