Tonearm mount on the plinth or on Pillar ?


Folks,
I am looking to buy a custom built turntable from Torqueo Audio (http://www.torqueo-audio.it/). They have two models, one with a wide base plinth where the tonearm would be mounted on the plinth (as usual) and the second is a compact plinth where they provide a seperate tonearm pillar to mount the tonearm. According to them the separate tonearm pillar version sounds more transparent and quieter because of the isolation of the tonearm from the TT. My concern is whether seperating the tonearm from the plinth would result in a lesser coherence in sound ? Isnt sharing the same platform results in a more well-timed, coherent presentation ? Any opinions ?
pani

Dear Pani,

The answer to this one depends on who you speak to.

The Cartridgeman, for example, swears by completely separate platforms i.e. motor/turntable/arm pillar for the air-bearing linear arm. For good measure he even decouples the Classic cartridge with a "spacer".

Although I like the Cartridgeman’s products a great deal I cannot reconcile the operation of the tonearm without close coupling (i.e. the so called "closed loop") but it wouldn’t stop me buying them ;^)

Technically, there might still be a closed loop even for the "separatist" approach except that the final connection is by means of a shelf or a platform. Then any variability would be introduced by whatever is being used to support/level the various elements e.g. 3 solid spikes relative to whatever material the supporting surface was made of.

Provided one could guarantee the T/T & tonearm stay in precise relationship at all times I wouldn’t see a problem. Trouble is that the tonearm is by nature constantly manipulated and messed around with by the User so personally I’d feel uncomfortable if it wasn’t locked down and immovable.....

Just my opinion though.... :(

Other posts here include testimony by folks who utilize "naked" plinths (none at all, only support columns for the motor unit) with separate tonearm pillars.  They rave about their results.

I've not tried that but I remain skeptical.  Just consider how critical the accurate set up alignment is for the stylus, then ask yourself how that can be achieved when the cartridge/arm mounting is not "fixed" relative to the platter/record?

So I agree with moonglum.  Plus I live on the West Coast where we are subject to earthquakes, some of which go unfelt.  I don't want my tonearm "dancing" around somewhere close to the correct position.

According to them the separate tonearm pillar version sounds more transparent and quieter because of the isolation of the tonearm from the TT.
This statement from the original post is false.

The problem you are up against is an engineering issue and is very similar to that of the steering and suspension in a car. Any looseness or flex in that system results in dangerous or scary handling!

Now in a turntable how it plays out is that instead of being scary or dangerous, it works out as a coloration: the platter must be as tightly coupled to the plinth via its bearing as possible, in turn the plinth must be absolutely rigid and acoustically dead while coupling the platter bearing to the base of the arm (which in turn should have no play in its bearings). Any divergence from this formula results in coloration.

The reason is simple: if the platter has any other motion other than rotation (for example a slight up and down that might be imparted from the plinth due to room-borne vibration), if there is any difference between that and the base of the arm the cartridge will compensate (since the stylus has to stay in the groove) with stylus motion and therefore a coloration.

So if the arm is sitting on a separate structure from the plinth, it is open to motion in a different plane and/or frequency as opposed to the platter and plinth. You really want it to move in the same plane and frequency as the plinth so that whatever that motion is can't be interpreted by the cartridge.

I am often amazed at how poorly understood this concept is.
 
czarivey,

As I stated, some quakes are not felt, but they occur and are registered.  So I may possibly have been listening to vinyl sometime while one happened.

But you missed my point, unless you were just being humorous.  The danger would be for my arm position to be shifted during that event so it would be out of alignment the next time I did play a record.  

I'd prefer that relationship (platter/record to arm/stylus) to be locked in place.

And thanks for weighing in with logic Ralph.