Eminent Technology ET-2 Tonearm Owners

Slaw
"I have to say that as regards to using acrylic as a platform for the vinyl record ......"

Further reading, TAS 40th issue.
Wayne Garcia on the new Rega RP8:

"Most notable is a two-piece, 16mm thick flywheel platter made of float glass, a technique wherein molten glass is Floated over molten tin in order to create the flattest possible surface and overall uniformity of thickness. To form the flywheel platter, Rega joins two separate pieces of float glass to the underside .... adding mass to the circumference.

Damn marvellous I say!

Yes, some interesting materials and ideas being used in platters these days. Isn't VPI also making a ceramic one?

Then the Clearaudio, in their Statement and Basis are using plastics.

Take your pick.

John I have owned 3 regas........all digital

Planet, planet2000, my current Saturn of 8 or so years ?, is one of my current digital players.
It sits on 3 symposium rollerblocks

Rega was one of the last companies to enter the digital world.

So I guess I like the company but I have no experience or knowledge of their analog items.

The RP8?

how do you put an ET2 on that ? :^)

I imagine TT designers trash many prototype materials before arriving at what they choose for their product. It should be a requirement imo, especially for some of the higher priced tables to understand the room/gear used to arrived at a turntable design.
This should be published information.

Regarding building turntables and materials used.

Here is a list of materials along with a number beside them. The number indicates the materials ability to pass thru sound (a high number) or hinder sound (a lower number).

The higher the number allows a better pass thru of sound. the lower number deadens, inhibits, absorbs.

Material Z0 [MRayls]

aluminium.........17
brass.............37
copper............42
cast iron.........37
lead..............25
magnesium.........10
steel.............45
tin...............24
tungsten..........101
araldite..........4-13
brick.............15
concrete..........7-10
glass.............10-15
granite...........27
marble............10
slate.............12
all plastics......1-4
all wood..........1-4
except cork.......0.1
carbon fibre......30

This data is informational only and was taken from this site.

http://qualia.webs.com/plinthbuilding.htm

"Another property of materials is the acoustic impedance, that is, how easily sound passes from one material to another. Nearly all the data available is concerned with supersonic frequencies of sound, typically 5 MHz, so not really useful in the audio range. However, it does suggest that getting sound from one material to another seems to be dependent on their respective acoustic impedances, easily calculated as:

Z0 = p x c where Z0 is the acoustic impedance, p is rho, for density, c is the speed of sound through the material [longitudinal wave velocity]
Some acoustic impedances of common materials: Z0 in N•s/m³ /106"

So to transfer sound from one material to another effectively may mean using materials with similar acoustic impedances, or, to hinder transfer, (as in isolation), choosing materials with very different acoustic impedances.

What about rounded edges for the plinth/armpod materials themselves over straight edge; to better deal with resonances? This is done with speakers.

Chris.

My trash bin....
Too many years ago to count, I went about building 5 off BD TTs in quick succession. The platter was aluminium, bearing had a tungsten carbide thrust plate with replacable steel ball on the shaft. All five were of the same design, the difference being the plinth material. I simply changed the bearing, platter, motor and arm from one to the other.
#1 Laminated MDF. Slooow and colored
#2 Laminated hardboard( like compressed MDF.) Better but still slow and colored.
#3 Concrete. Hard and bright
#4,5 Slate. Quite good, slightly bright, which was mitigated with a lamination of MDF on its base. I sold #5 to a then Linn owner.
After this I went on to build 4 off unipivot arms. Based on the geometry of the Hadcock CH228. They all had saphire bearing cups with ss pins. Brass pillars and magnesium headshells.The only change was the wand material.
#1 epoxy resin infused balsa wood. This was not as stiff as expected and this was reflected in its sound, smeered and soft.
#2 hard wood dowel. Lovely, glorous, romantic but colored.
#3 undamped aluminium tube. Nice and clear with a slight rising top end.
#4 damped thin wall glass tube. Easily the best. Clear and articulate. This was broken awhile later during transportation and I was too devistated to rebuild it.

Does any one else have similar war stories? I am interested in your findings.