Inner groove "Rumble"

"staccato-like popping" Can you guess in what frequency range? Rumble is very low frequency stuff, as the name suggests.

Yes ...... low frequency.

Once my ground wire fell off and I heard "popping" noises. As a record spins, a static charge builds up on the vinyl surface. Normally it would flow to the spindle, which is connected to the chassis ground and out. In the absence of a path to ground, the static would discharge to the cartridge itself. In your case I think it's a coincidence that it occurs as the cartridge nears the spindle, the record has been spinning for 10 to 15 minutes building up more static electricity with each revolution.
Check your ground wire.
Rich

Thanks Heyraz ..... but Rega tables do not have a ground wire.

Rega tables do not have a ground wire.

Interesting. How do they get rid of the static charge that builds up on the record surface as the spinning vinyl platter "rubs" against the surrounding air molecules? It has to go somewhere otherwise it "sparks" to the nearest path to ground.

Before I realized the ground wire had fallen off, it sounded like a dirty record was playing (background noise) with the occasional "pop" caused by the arc to ground. I nearly tossed out a perfectly fine record thinking it was too contaminated to save.

Is it really rumble? Have you used a test record with various tones to identify your tone arm/ cartridge cantilever's resonant frequency? When my test record plays the resonant frequency, the entire arm/cartridge assembly visibly shakes. Have you moved any furniture or speakers in the room that might have affected the acoustic characteristics? If my speakers are too close to a corner, the bass can get boomy.