VPI Prime Sig/Lyra Delos / Feedback ...help!

@tommypenngotti You learn something everyday. I can slam my Sota with a mallet and you can not hear a thing. That is because the "butcher block" is hanging inside from 4 springs. Edgar Villchur was fascinated by the problem (which he also created with his loudspeakers) and Came up with the AR XA in the late 50's. It sold for something like $67.00 and within a couple of years everybody had one. They were outperforming turntables costing over $500. You could not get one to feedback if you tried and they didn't sound like an express train in the background. I never got an AR. My first suspended table was a Linn LP12. You need to get a real suspension platform. I am familiar with MinusK and Vibraplane. To isolate a turntable you have to use a mechanical filter, three of four springs tuned to a resonance frequency below 3 Hz. Bob your head three times in a second. That fast. You have to use springs just stiff enough to support the turntable.  

So I just bought a 2" butcher block that's (solid AF) & 4 IsoAcoustics pucks,

@tommypenngotti Just so you know, a 2" butcher block doesn't do much to kill vibration. If you bonded it to a substantial slab of marble or Corian (or other dissimilar material) the two materials could rob energy from each other and thus actually be able to absorb resonance.

I had a problem with foot falls near my equipment stand being audible despite some very nice anti-vibration platforms (I didn't have a problem with feedback otherwise). That was solved by placing bearings beneath the equipment stand, which relieved side to side energy.

When I was having footfall issues in my office setup, the ISO Acoustics pucks didn’t do jack to help. A maple butcher block was also completely ineffective. The shockwave of heavy footsteps on bouncy floor induces a (relatively) huge displacement (mostly lateral) in your turntable / tonearm system. The displacement is going to excite every subsonic resonance (e.g. cartridge suspension) and cause skips. It also excites a Clearaudio ceramic-magnetic bearing, btw. And also their magnetic bearing tonearms (good luck with that lol).

Spring suspensions (and maybe roller bearings) can help to some degree, but they won’t always be enough it if the problem is really bad. The old "bang a hammer straight down on the plinth" test is NOT a good simulation of this issue - though it was great gimmick for selling tables! Other platforms (e.g. butcher blocks, HRS, Symposium, CMS etc) and isolation feet are completely useless here. Bracing the rack against a strong wall, or a solid wall mount, is the only "real" solution in these scenarios - because they’re the only techniques that limit the displacement. One of worst audiophile "anti-patterns" might be sticking a turntable atop a tower style rack, unbraced. 

But OP’s problem is NOT that. It’s a resonance - in the audible bass frequencies - which I’ve noticed myself in the VPI arms, especially the 3D printed ones (especially the earlier ones - it’s a bit less on Fatboys).

You know, a lot of people switched from the VPI metal arms to 3D printed and commented that drums sounded so much more real and powerful! Well, guess where that resonance frequency is positioned and and what it sounds like...lol.

@mulveling 

I think Im chasing ghosts here...rabbit hole of trying to isolate came up with Hana ML & metal tonearm (which does not feedback) just looking for best possible isolation. When I get the Lyra back I'm going to switch it from the 3D printed arm to the metal arm to test...but I think I already know the answer 😃 plastic vs metal. 

end result - 

received completely rewired arm back from VPI and it works fine with Lyra now 

2 variables : 

1. Changed out to HW-40 feet 

2. Moved TT to middle of cabinet away from speakers