Question re speaker or amp problem???

I have a pair of KEF Reference 102/2's and have been (in the interim) powering them with an old Luxman L-80V integrated amp (1974). I have noticed on occasion with both my Monitor Audio's and the KEFs that while listening a very moderate levels that the sound in one channel gets crackly or static. When I get close there is clearly distortion. Then the channel stops working. When I turn the volume up a little bit the sound is fine. Is this the speakers or the amp?
Probably the volume pot (contacts needs cleaning) or a lose contact somewhere along the line b/ween amp & speakers.

Nothing a good contact spray or (if necessary) some soldering can't fix.