Turntable vibration from walking on wood floor

[Tomas]

Does anyone have some idea what I could do after I have tried the following troubleshooting?

Linn Sondex LP-12. Have good solid wood cabinet which it sits on.
Tried a slab of granite underneath the turntable. Still skipped when I walked on wood floor.
Tried a thick foam rectangle underneath the turntable. Still skipped..
Tried combination of foam and granite as sandwich. Still skipped...
Tried all sorts of isolation pucks, rounds, etc. Expensive and did not work!
Bought a Linn Sondex LP 12 Base. Solid wood very expensive. Did not work.
I don't want to put up a wall shelf. !!!
If I put small squares of granite or marble under each leg of the cabinet would that work? (Legs are short 3" )
CJ Amp is 75 pounds and Turntable is also heavy so I would not try this unless someone thought it had potential!

I love my Linn with Conrad Johnson Pre-amp and Amp. Benz Ruby MC/Graham custom Arm. Sound is glorious!!! Seductive!!!!
If I have to I will just enjoy it alone with me not walking while the record is playing. But it would be nice to not have to be so careful walking up to the turntable while it is playing.

Thank everyone for any help at all!

[admin]

Have you adjusted the stylus tracking force to appropriate setting? It may be skipping if the counterweight is too much.

What kind of flooring do you have? I have my listening room over a two car garage and ended up up putting a crossbeam across the garage to stabilize the floor. They build houses completely out of wood where I live (other than the foundation) so it tends to move a lot. It worked really well. But I never had skipping even with the old floor.

If you are jumping up and down on a loose floor I can see skipping, but normal walking should not really cause those problems.

[AnotherJohnson]

LP12s are tricky to set up.

The subchassis has to exhibit what Linn call a “pistonic bounce.” The leadout cable has to be perfectly dressed.

LP12s do not respond well to adding mass to their support structures.

The guideline is to have a light and very rigid support structure.

Peter Swain, owner of Cymbiosis (in my view the best LP12 setup guy on the planet) has provided a free setup manual on the old, now closed, Linn Forum. It was migrated to the Linn section of HiFi Wigwam. I’ll try to post a link.

I have been fettling LP12s for 35 years, and have learned much from Peter. Perhaps the best guy in the US is Thomas O’Keefe in Ann Arbor. Thomas is a bit more closed mouth in helping, but he knows a lot.

Where are you? And who set up your LP12?

I’m in Middle TN, US. I have the setup jig, the specific tools, and have built and rebuilt LP12s successfully. If you’re near me, perhaps I could offer help.

[AnotherJohnson]

https://www.cymbiosis.com/downloads/

Three parts. No longer on Wigwam, but available directly from Peter.

[AnotherJohnson]

FWIW, I use a Target shelf in one system and a light rigid table in the other.

The shelf works well in my situation because the wall is 2x6 construction and well braced, so acoustic feedback is not a problem.

[AnotherJohnson]

Walking is typically at the rate of near 1 foot fall per second.

But each foot fall is equivalent to a somewhat squat unit step input, which FFT analysis would show to have a fairly broadband frequency domain content.

What this means is that every step excites the floor’s natural frequencies, which are most likely in the 4 to 8 Hz range. The subchassis can only filter these out if it’s properly tuned.

The dampers should be functional (not old and hard), and the three springs should be adjusted so that when the plinth is level, and the cable is properly dressed, the subchassis/platter/arm/cartridge/record assembly should ONLY move in the vertical direction if it is displaced. No rocking allowed. That is what is meant by pistonic bounce.

Adding mass just exacerbates the problem. Adding foam and mass is a hit or miss proposition, and I’ve never seen a case where it helped an LP12. But it is cheap to try, and maybe you'll luck out.

If the Lp12 is set up optimally, and there’s still a problem with footfall, then the order of addressing it would be

1. Light rigid table mount
2. Wall Mount (not recommended for flimsy walls)
3. Upgrade floor (support to put a node at the TT installation if possible, which means a tie that location down, and alternately any additional floor supports will have the effect of stiffening, constraining, and raising the natural frequencies of the floor. Adding mass changes the natural frequencies as well, but it tends to push them down further, and so exacerbate the problem.). 'A concrete slab on the ground floor offers a lot of mass ... but it is not the mass that helps, it is the lack of deflection under loading. Acoustic response of walking on a concrete floor can be easily heard, but most of this is the sound of the air being squeezed out between the sole or heel of the shoe and the very rigid concrete. The best of all floor worlds for good vibration and good acoustic performance is a carpeted slab installed directly on the ground, hence fully supported. The pile of the carpet cuts the slapping noise of the shoe fall. The slab on the ground isn't prone to deflections. But obviously, this is not a very practical retrofit solution.

FWIW, Both Peter Swain and Thomas O'Keefe have historically been available by phone (Cymbiosis in Leicester, Overture Audio in Ann Arbor respectively).

Thomas also imports Frederick Lejonklau’s electronic gear to the US from Sweden, and last I knew, he was also handling a line of furniture that was built along the lines that Linn prefer.

Peter has a web site (cymbiosis.com) and some other staff who may be able to offer assistance. And then there is the Linn Owners Club of the HiFi Wigwam, although that's not nearly as active as the old Linn Forum was.