Speaker Cone movement

[Jimbo]

When I turn the gain up to maximum ,without music playing, on the phono section of my valve amp I have noticed the speaker cones fluttering with the tube rush.

Anyone know what causes this and is it a normal phenomenon with tube valve amps?

[technobear]

Sounds like subsonic seismic vibrations picked up by your turntable. Do you live near traffic?

[walpurgis]

How old is your amp? It could be a cap or other component out of tolerance and either causing LF components or allowing some LF through. My old Leak Stereo 20 did the same until I recapped it.