[prepress]

Originally Posted by Formerly YB-2

Nice TT/TA/cart.

However, your info makes me wonder about your cartridge alignment.
One reason is how far out the cartridge is sticking from the headshell (though I've owned a 309 and a Grado, never together) in your pic.
The other reason is how dirty your stylus was. A badly misaligned stylus will 'shave' the vinyl and build up a little brown ball of 'vinyl fuzz'.
Hope all is well.

Originally Posted by prepress

A quick inspection shows the new cartridge's body is bigger than the previous one (it's a different cartridge) and the screw holes are situated further back. I attached a photo of the headshell with the previous cart for perspective. The previous cart was a Sonata Reference; the new one's a Sonata 3 Timbre

As for the alignment theory, I will be in touch with SOTA tomorrow and plan to bring that up. Thanks for the suggestion. The "rumbling" I described was actually the musical signal but muffled as well as being very low-volume. They did play the Sapphire before shipping it, reporting that it sounded great, but I've no idea how it could get so dirty or gunked up between then and now. And since the muffled sound came out of the gate on my end, something had to happen between then and their listening session. Interesting.

I got an e-mail from Christian at SOTA a while back. The problem was using dirty records, says he, and that he would bring it up with the staff. That is plausible, so I'll leave it there for now. My (admittedly superficial) inspection shows no other issues.

I haven't had much real opportunity to play records, but what I have played sounded good. In fact, at times it sounded as if I were playing a CD, nice and crisp. On Santana's Inner Secrets, the cowbell in One Chain (Don't Make No Prison) was in the room!