Tube power amplifier low static on one channel

Hi all I have an Audio Note Kit EL34 power amplifier. When the music is off I can hear a static sound from the right channel. It is not constant it gets louder then quieter then nothing then back again. I switched the non power tubes right to left and the static stayed on the original channel.  

If it was a tube it would have switched to the other channel correct?

If it was electro interference it would come out of both channels correct? 

Thoughts on what to check next?

Thanks

jh