Soft ticking noise when using Amp Selector

[drchevalier]

Hi,

I have a very old and proven Amp Selector. I have three amps connected to it right now, two Marshall heads with 4x12s and a PRS Dallas

When I select either of the Marshalls and am not playing, I can hear a subtle ticking coming from the Marshalls about every two seconds or so. My guess at the timing may be off but the pattern is regular. Trying different outputs on the Amp Selector makes no difference. I do not hear the ticking in the PRS. If I go straight into the Marshalls, I do not hear the ticking. When the amp is not selected it is dead quiet as expected. The Amp Selector goes direct to the input of the head. The 2500 has a UA OX between the head and the speaker cabinet, the CSL is direct to a pair of 4x12 cabs. I probably never noticed this before because I am now able to play a bit louder and that has raised the base noise floor as would be expected. I do not notice a difference in the ticking regardless of channel on the 2500 and the CSL is single channel only. The CSL has no effects loop, and the GMajor that was in the effects loop of the 2500 was removed.

In front of the amp switcher is a Cusack Loop Switcher. Each effects pedal is in its own loop, and the buffers in the Cusack are on. The guitar signal runs into an Ernie Ball volume pedal and then to the Cusack. The Cusack loops are isolated.

The amps are plugged into Furman power conditioners and the only place that I could see some weakness is that the Amp Selector, the pedals and the Cusack are all running off a Donner isolating power supply. It is an admittedly inexpensive device and I can replace it with something better (or multiple somethings due to power needs) but I wanted to know if I had missed anything that anyone could see. I am only using input A, and am not using the Tuner/Thru output as the Cusack has the Tuner in a dedicated connection that silences the device when the tuner is engaged.

Thanking folks in advance for suggestions.

Ross