A Copernican View of the Turntable System

The base as an island, I am not sure?

The fundamental objective of turn-table design is to maintain an optimal geometrical relationship between the stylus and the groove in such a matter to allow, as Halcro so eloquently said it (paraphrasing), the cartridge to transmit perfect information by moving up and down frictionlessly to allow for correct VTA as the groove modulates.

This in turn consist of two factors the geometry and the maintenance thereof. Geometry is the initial location (for the lack of a better term) of the tone-arm pivot point, stylus contact point and center of rotation of the disk, such to achieve Baerwald or Stevenson setup (or whichever one you believe to be best) and including optimal azimuth and VTA. Maintenance is the ability to prevent outside factors such as vibration and noise to change the optimal geometry.

Now to separate and isolate the arm pod from the platter, in perfect world, seems to address the maintenance issue. If the arm pod is isolated, any vibration from the motor or bearings will not be transmitted to the tone-arm or stylus.
This raises the question how is the arm pod accurately located in relation to the platter? Many of the systems in this thread show the arm pods simply placed alongside the platters with no means of accurately locating relative to each other (this is an appearance based on the photos) clearly these tone-arms are properly setup, but how accurately (initial geometry) and what prevents them from moving over time?

Ultimately, the arm pods must sit on a surface that is shared with the platter. The platter is isolated from this surface by pneumatic footer or other method, which no doubt prevents the platter vibrations from transmitting through the surface back to the tone-arm. But now since the platter location is no longer rigidly held relative to the tone-arm pivot, other environmental factors, such heavy footsteps on the floor or ambient noise, can cause these distances to change momentarily (vibration) or permanently (until readjustment). Is the arm pod as an island truly ideal?

A rigid location of the platter vs. the tone-arm pivot ensures optimal geometry, and high mass plinth minimizes the impact of vibrations and noise from the platter. Then isolate this assembly from the room. Is this approach not superior?

Halcro, I am not opposed to your approach, in fact I find it attractive. Your idea of the concrete arm-pod seems like a fun DYI project that I have considered for use on SL-1200 table. But that got me to analysing this approach and the big hurdle I see is locating the arm-pod.

Really my question is how can you guarantee this geometric relationship when considering using a Baerwald type set-up. With this type of setup we are taking about degrees of precision in fractions of milimeters. I have trouble seeing how simply placing, with out any means of mechanical fine adjustment, an arm-pod on flat surface(albeit very diligently and carefully)can provide such a degree of precision. Can you explain the approach you use?

One Idea I came up with would be to have mounting locations machined into the base used. But in doing so you then be coupling the arm-pod and turn-table to the mounting surface, and you would essentially be back at square one.

Dear Raul: I feel that your posted of 9-11-11 was a direct response to my posts. I would like to make two points in this regard.

First: Being critical of a given approach or "road" as you put it, does not mean that one is against it. I doubt that the purpose of this thread or Audiogon in general is to host forums where people spend there time complementing each other's system. (BTW you have a very impressive system). Being critical challenges these approaches and helps them evolve. While receiving complements is pleasent (I enjoy receiving them as much as anyone) they will only lead to status quo or possibly shinnier and more expensive systems.

Second: you suggest that unless we try a given approach we cannot comment on it. Once again, then why participate on A'gon. I thought the point was to gain from the other participants' experiences and mutually advance. Moreover, I do not have the means to try all that I would like to.

With this said, Raul and the others, please explain the following. With the TT mounted on a suspension system above a mounting surface and the armpod rigidly seated on this same surface how is the distance that must remain fixed between the pivot point of the TT and the tonearm fixed?

The trade off, is between the variations in this distance, most likely in scale of 1/10 to 1 mm vs the variations caused by the micro vibrations from a bearing of a shaft turning at 33 or 45 rpm with a scale in likely 1/1000 to 1/100 of mm. My instinct would lead me to believe that the first problem is far more problematic then the second.

I view placing my rack between my speakers a lesser evil. I have very small room (16x10x8ft or 5x3x2m LxWxH). I simply do not have anywhere else where it can be placed other than in a corner, which is worse.

There is one place where the rack could be placed but I would then require long interconnects (20ft RCA's). As result I would trade off mechanical problems for electrical ones.

This sport is all about trade-offs, at all levels from the tone-arm to the room.

This thread moves fast, so pardon me for stepping back a few days.

Jcarr: Thanks for the response to my post regarding the placement of my rack. I recently changed my rack from an Ikea shelve that was low and wide to a proper rack that is tall and narrow. The change in dynamics and bass response was dramatic. The new rack as far back as it can go but less than 500mm (20") back from front face of the speakers.

Besides the the interconnects there is also the issue that my dedicated power line runs to an outlet located on the wall between the speakers. Moving the rack would require pulling the wires again or a long extension cord.

All this is to say, that my experience with the change of rack leads me to agree with Tuchan's statement that the most limiting factor to good sound is the room. Understanding and taming your room and its contents will likely have bigger impact than any gear upgrade. That is not say that good gear is not required, it is necessary but not sufficient.