A Copernican View of the Turntable System

Dear Geoch and Henry – thank you for providing very valid points for consideration. My current armpod has served its purpose - it was built to determine if this approach was valid. It was not expensive to make as materials are available and cheap where I live. I am ready to setup up the next one.

It can be done in stages and allow me to use at each stage. I enjoy the DIY approach so would like to continue this way - Thinking of a 4” diameter brass cylinder pod and to mount my Tonearm directly to the top of it with three steel spike couplers on the bottom. This would be the first stage.

I then would make a decision on whether to add a top plate of aluminum to the brass. I need to think more about what has been said here about this.

I was speaking to Bruce of Eminent Technology who informed me that my tonearm uses Cone Point Set screws to level itself to the base. These come in many lengths and diameters.

http://www.radax.com/store.asp?pid=15198

I could mount the top aluminum plate on the brass using the same approach. 3 of these screws close to the perimeter to level it. 2 or 3 bolts would then be placed “just outside of the footprint of the tonearm base” that it will sit on it to secure it to the plate. The plate would ride on air as well as the tonearm. Do you feel this air is an advantage or does it not matter ? Can I get your thoughts on this.

From a DIY point of view - It seems to make more sense if adding this plate to just have it touching the brass at specific touch points with the set screws and bolts and making sure no movement and it is rigid.


I did some research today on materials and pricing.

Metal Supermarkets is located in Canada, the US and the UK.

http://www.metalsupermarkets.com/MetalGuide.aspx?CategoryID=BRASS&ProductID=TUBE_ROUND&ProductSubCategory=360

Prices are for solid brass and SS armpod cylinders. Prices are in Canadian dollars.

4" diameter brass (360 grade) 4 inches high - $152.55 (16 lbs)
3” diameter brass (360 grade) 4 inches high - $79.91 (9 lbs)
4” diameter Stainless Steel 4 inches high - $94.81 (15 lbs)
3” diameter Stainless Steel 4 inches high - $59.71 (8.5 lbs)
3” or 4” (7 mm - approximately ¼ inch) brass top plate is about $10.

Dear Chris,
The stainless steel pricing looks better than the brass. The only down side is it is harder to mill yourself so you might need a professional machine shop?
I'd go for 316 grade rather 304 as it does not tarnish and is definitely non-magnetic.
I can't quite follow the 'air' reference to the top-plate? I personally would want the top-plate connected to the mass of the armpod as securely as possible. In fact the only reason for a top-plate IMO is to allow clamping of the tonearm and connection of the Din cable, otherwise I'd happily screw or clamp the tonearm directly to the armpod.
Cheers
Henry

Dear Chris, I present to you my reservations about the possibility of ringing. The 7mm Brass is a lengthy piece and the porpotions are not quite ideal for doing this "air" mounting. Furthermore I believe that the 3 tiny bolts are not so absolute idea in terms of controlling the resonances, even if they can provide the convenience of alignment, the threaded holes together with the asymetrical body of the tiny bolts , are not comparable with some pretty harder & perfectly round bearing balls in order to detune the armboard resonance & above that, in terms of rigidity are more secure.
I'm with Halcro at this. You better try the massive & solid approach -as the more secure way- that is also more tolerant to some crafting inaccuracies. Also keeping the project simple is always the better way. I agree with your choise of Al plate / Brass pod / Steel spikes for your next project. (Although I prefer the Symposium Rollerblock JR instead of spikes)

Geoch/Chris,

I'd be careful about using Rollerblocks beneath an arm tower. The ball bearings are not secure enough and movement when lifting and placing the arm would almost certainly create ongoing alignment problems. In fact, the only place that I find the rollerblocks ideal is beneath my CDP, where mechanical movement is minute enough to never create a problem and yet the benefits can be easily heard.

Here in Greece it is common place the Rollerblock JR under really heavy mass loaded free standing arm pillars when we are using parrallel tracking arms.