Tube Phonostage Causing Rumble and Noises

Thanks everyone for your feedback and advices. I think I will take the easy way out, ie play records without the sub.

Thanks a million.

@mulveling 

“With the Fatboys (both uni and gimbal) the problem is mitigated enough to no longer be a concern.”

Sadly, this is also the Fat Boy — Kevlar 3D printed.

I also have the Esoteric Grandioso turntable.  Same issue when I used the Van den Hul Frog Gold cartridge, so I think it’s the cartridge, which is otherwise lovely.
 

I two huge SVS PB 16 ultras and Bowers 800 (Diamond) to fill a big space and I like to listen loud.

I measured and had an off the charts standing wave peak about 1.5 feet off the front wall.

Regardless of what is picking up the feedback, the base trap solved the issue.

@davetheoilguy 

Interesting - still so many surprises and lessons to be had in this hobby! That's cool you were able to isolate the problem to standing waves, and resolve with acoustic treatments. I *think* the majority of my issue here was structure-borne energy, so that is indeed different (moved rack around a lot trying to avoid the worst of standing waves and structure-borne energy). I've recently had the Frog Gold on the Fatboy here. And agree - it's such a lovely, well balanced cartridge!

@mulveling 

I’d love to say I’m an acoustic genius, but I figured out it was a standing wave because every time I went to look at the turntable to figure out what was going on, the sound would rapidly fade (and my heart would start beating way too fast, which I figured out was relevant later).

A very Heisenberg’s cat situation.  I’d look and the sound would go away.

Eventually it dawned on me that my body was breaking up the wave.  Did a little trial and error and then tests to confirm.

The weird heart rate is a classic symptom of intense subsonics, which I knew from working in a haunted house when I was a teenager.

This whole OP issue is odd.