Nude Turntable Project

The Gyro testing table had 6 cast iron legs. Five of them were height adjustable with wooden decoupling pads. The sixth leg had no adjustment and it directly coupled with the concrete floor.

Interesting

gave this more thought. My current version Sp10/Armpod testing TT is different from the Gyro as it is a rigid structure bolted into the base/plinth. No provisions for height or level adjustments. All height and leveling adjustments are done by the three adjustable AT-616 pneumatic footers under the base/plinth. In this case the actual TT system feet are these footers and I use three.

As noted earlier the ET2 tonearm has its own leveling system independent of these feet for final leveling. I level the platter as best as possible then the tonearm. My SS legs are acting as supports and are not the actual TT system feet. I would want to keep all four for stability and rigidity. Sounds to me like trying this out means changing out one of the AT-616's for an alpha leg ? The one under the tonearm in the pic ?

Halcro/Pryso
We are in agreement on the "stability" of 3 feet.
My comments on stability are in the context of draining unwanted energy using single point mechanical grounding. I also assume the tripod is correctly designed for weight distribution to give stability and deal with rotational energy around the central axis. I also assume we are not driving the TT down to the grocery store and we are not in the habit of sitting on it.
Very few surfaces that the gear is mounted on are truly level, and in that context 3 feet will naturally load predictably, whereas with 4 or more feet they will have to be adjusted precisely to provide predictable loads through each foot. This is almost impossible unless you have pressure pads under each foot. The Mana stand manufacturers' recommended set up procedure for their 4 legged stands were to adjust the 4 feet with a stethoscope and tapping technique. Imagine doing this on each shelf as well as the feet ! And if you have a wooden floor that moves, you'll need to retune them each season.
In my 30+ years of audio I have applied the Goldmund mechanical grounding principles on all my components ( and many others ) and in all circumstances converting equipment ( TT's, amps, speakers ), speaker stands etc to 3 feet, single point mechanical grounding has yielded significant improvements in clarity, focus and the removal of resonances and tonal distortions.
In the Goldmund amplifiers, the mains transformers are grounded directly by bolting the transformers to the Goldmund footer, and the transformer is attached to the chassis by lossy connectors. The electronic circuitry is directly coupled to another of the 3 feet for optimum grounding and that foot has a lossy connection to the chassis. The net outcome is that each of these sources of resonance are single point mechanically grounded, and separate from each other, even though they exist in the same chassis. The chassis is decoupled from the others and grounded through the third leg. With non Goldmund amps the "alpha" leg is best placed under the mains transformer which is usually the largest source of resonance.

I haven't been on this site for a while and just caught up with Halcro's brave changes. I admire your "out of the box" thinking, Halcro. I could never feel comfortable looking at the electronic guts hanging out of my TT.

My TT-101 is now seated on a "SolidSteel WS-5" brand wall shelf - which is bolted to a brick wall. This wall shelf is a heavy steel perimeter frame supporting an mdf shelf which is leveled by 4 spikes into the steel frame.

This excellent support - perfectly leveled (plus I did another adjustment to the height of the bearing thrust plate) has solved all of the start-up problems it was having. It starts immediately and runs at exact speed without hesitation at the push of a button - just as it should.

The turntable sits on that mdf shelf using it's original steel can resting on 3 perimeter brass heavy points and a 4th heavy point sitting dead center under the can. That 4th point is a drain for the can and is important even though the can is damped.

I have discussed at length how the can is a major problem and needs extensive damping. Mine is lined with bitumen damping sheets (about 1/4 - 1/3 of the venting holes remain open) and has a heavy rubber strap around the top where it mounts to the structure of the TT. Even though only a fraction of the ventilation holes remain in use there is no heat build up - the can stays cool to the touch after spinning for hours.

I believe that I have reached a stable point and will leave well enough alone. Ella Fitzgerald is scatting in agreement.

Aigenga wrote---"This excellent support - perfectly leveled (plus I did another adjustment to the height of the bearing thrust plate) has solved all of the start-up problems it was having. It starts immediately and runs at exact speed without hesitation at the push of a button - just as it should".

Is it possible to explain further how this is accomplished and also post some pictures to help a layman like me to fully understand what you have done.

Which part interests you - the leveling or the thrust plate adjustment?