spring loaded platform non-suspended turntable

I put my Rockport Capella II on a pneumatic anti-vibration table, similar to that under the Sirius III, and experienced considerable improvement in term of background blackness with no negative effect that I could hear.

My friend put his Technics SP10 MK2 on a Minus K and got similar improvement in background blackness, but I was not familiar with the system so couldn't tell whether there was any negative effect.

However, the Minus K is not self leveling, so if the CG of your TT is not exactly at the centre of the platform you need to add some weight and move it around the platform to level it.

Let's see, if you have an unsuspended turntable on a solid unsuspended base, the structureborne vibration can get right up into the turntable platter, the tonearm and the cartridge. That being the case, I would probably opt for some kind of vibration isolation system.

I believe a cheap experiment would be to put some sort of inner tube, perhaps from a motorcycle tire, under the table and inflate it till it "floats". That should let you know more for little $. I have a VPI Classic that sits on a very old VPI isolation base. It has a sandwich platform, metal outsides over wood, and four foam wrapped springs in the corner. That sits on a wood rack I made, and on a hardwood floor. I can make the arm skip if I step near too heavily, but there is no acoustic feedback.

Fingerpaws...oh yes you do have acoustic feedback...its just not at a frequency that you can call it that..however, it is blurring the sound coming from your turntable. Your fix (given the springy floor), is to mount a shelf on the wall for your Classic - affix it to studs. ( had one of those VPI spring things too). Get it off of that.... Get Bearpaws to replace your mini feet, and be delighted at how much more clear sound you get...more definition, more bass, clean, clean, clean.

Stringreen, I respect your musical knowledge and experience, but I believe you are wrong about "acoustic feedback". My simple understanding is that it is the airborne (i.e. acoustic) waves from output back to input. The most common example most of us have heard is an improperly set up microphone in a auditorium which howls from the sonic loop from PA speaker back to the mic.

Similarly, a turntable/arm/cartridge system is subject to the sonic energy, particularly low frequency tones, from the speakers. Wall mounting will only be effective if it moves the tt system away from a bass node loading area. It is not related to a springy floor. In extreme cases I've seen the tt system placed in a separate room from the speakers to minimize acoustic feedback. Fortunately most of us don't need to go that far.

This is why I suggested consideration of all three conditions for unwanted energy in my post above.