As Ecca says especially with single coil guitars there's all kinds of interference just waiting to show itself, the strings do make quite a good aerial you know

Can you be more specific about the noise Dave ?
Is it mains hum, is it constant or modulating, is it rustling/hash type noises, is it a hissing type noise ?
You could try pulling then re-seating the valves in the etap, costs nothing & might just throw up something
Dick.
You didn't mention the DeArmond pedal, good to hear there's some progress.