Why are my woofers pumping?

If you’re hearing a periodic bump and it’s keeps a perfect rhythm, has to be in your transport, except you said it does it on cd too. 🦄

Yes I will tell, once I find the culprit. The subsonic pumping does not occur with CDs, only vinyl. It does occur when I play digital recordings (rips) of my vinyl. Since these were made with zero speaker volume, acoustic feedback is unlikely. As I've said before, my phono preamp needs balanced out, single ended sounds far less good, so the single-ended KAB would need some kind of cludge to work. If KAB had lived next door I would of course have tried it, but it requires ship across the atlantic, tax etc - for what probably degrades the sound even if it takes away rumble.

Dear @o_holter : ""  full SS phono pre - yes, good idea. But again, I wonder, if this would solve the mystery. ""

you will know when you try it. It does not needs to be a top SS unit because is only to make some tests.

If you have the opportunity to do it then you must to do it. You can lost nothing but time consuming.

R.

O_holter: Sorry I misunderstood you, conerning the bump during cd playback.  Since it's only when playing vinyl, common sense dictates it has to be in your TT.  Too bad u don't know someone who could bring their TT over for an A/B comparison.  Good luck. I'll be very interested to know what u find.                                                 Steve in Tennessee. 

@o_holter , if its happening once per revolution regardless of the LP, its a defect in the turntable. Could be a bad bearing (which is why I specified grease earlier, rather than oil), could be something that rubs on the platter or it could be the platter out of balance, and shifting on its spindle as it rotates.

The preamp is clearly off the hook. To test this I would simply borrow a turntable, it does not have to be expensive, just to try out.