Subwoofer rumble issue

No not telling you to, would never do that Paul, but beside putting the TT in another room, it was the only other fix for me with bass that goes to very low frequencies.

Just dawn on me, if you have any tubes in the chain, these can go "microphonic" some call it "euphonic" (w**k w**k) and this can cause runway bass oscillation also.
If you have then do the finger nail light tap test on these just like the plinth test, but without the stylus on the record this time.

Cheers George

Ok I’ll try that test and report back. Thx

years ago I lost a bass unit on a rega jura. The combination of TT, room, track and record warps led to a loop that saw the drivers very quickly oscillate more and more until the paper cone literally tore open around the center area, this took less time than I could get over and turn the volume down....the other driver survived the experience, I don’t think the voice coil burnt out but somehow the extreme excursion caused the cone to rip.

Hey George - tubes seem to be ok. I’m running the Phonomena II through the aux so I’m assuming the preamp tube(s) in the amp aren’t being utilized, right?

Where and in what are these tubes situated, if in a tube preamp (model?) and your using the aux input you are still fully using the output buffer tubes of the preamp, but you say they seem to be ok?
So then I'm affraid we come back to the air-born feedback.

Cheers George