One of the most frustrating problems I have encountered is trying to figure out what is causing intermittent static. For over a year I struggled with it on my Paramount 2A3s. The problem didn't follow the tubes, indicating the amp was the problem (or so I thought). Tried cleaning tube pins, looking for cold solder joints, replacing tubes anyway, carefully probing for loose wires while I listened--nothing.
I bought a new rack and had to rearrange things. NOW there was intermittent static from the OTHER amplifier. WTF! In addition, another amp below the Paramount on the same side of the rack started having intermittent static.
It was one of those "how could I have been so stupid" moments. I had placed our wireless phone hub/base by the first Paramount, and when I rearranged the rack I placed the base by the 2nd Paramount. Moving the phone base 15 ft away solved the problem. Don't put noise/RFI-generating equipment near your amps!
