I have a WA3, and it has started making a high pitch whine. It is audible without the headphones on, very very high frequency (if I wasn't in my 20s I wouldn't hear it). A similar frequency noise happens in the headphones too, on and off.
Changed the tubes, still the same. At first I thought it was the tubes because if I lightly tap the 6080 tube (a 5998) it stops, but then comes back. Moving the volume knob doesn't affect the annoying noise, music masks it but it comes through in the silence at constant volume regardless of volume knob position.
It is quite intermittent but noticed it getting more frequent.
Any ideas? I can put up with it, but would rather not :P