A Copernican View of the Turntable System

Dear DT, All I'm saying is can you direct us to such a diagram or help us understand how you would go about constructing it? One major force, for sure, is the torque of the motor, which is angular by the definition of "torque". And we all know that the torque of the motor trying to compel the platter to revolve in a clockwise direction will in equal measure compel the chassis to revolve in the counter-clockwise direction (which is one reason, IMO, why there MUST be at least a certain minimum mass to the chassis of a direct-drive turntable, where the motor is firmly a part of the chassis, lets say it needs to be much higher than the mass of the platter). Apparently the no-plinthers have observed that Newton's Third Law is not much of a problem in this regard. What next, I mean what other major forces are in play? VTF, skating, gravity.....?

One of the senior members in the other forum I am part of said something about isolated arm pods in a way that I think “nailed it” as far as what I am hearing.

"These are said to break the rumble feedback loop through the plinth as it contacts the arm at both ends - through the arm pillar and cartridge via the platter".

That’s it for the theory part.

Dear Lewn:

I thought in the other thread that you were going to attempt this with your Denon. I was really looking forward to your impressions based on your vast experience.

Your comment:
“Apparently the no-plinthers have observed that Newton's Third Law is not much of a problem in this regard”.

Btw - Thinking of having T-shirts made up that say NO-PLINTHER – just kidding. Just remember I still have another TT with a plinth that I enjoy.

Anyway to answer the question - When I start my sp10 there is a slight split second vibration that can be felt in the motor casing. After that it might as well be dead – can’t hear or feel anything and it hasn’t moved at all since it was last set up.

All

I have to admit I am a little dumbfounded at some of this. Vector diagrams?

If trying a separate arm pod and no plinth “around -holding ” the TT meant lots of investment in time and $$ - I would understand the reluctance– but its been discussed many times by Raul and Halcro - all you have to do is take the motor/platter unit out of its plinth, put it on some type of legs and construct some type of temporary arm out of some cheap material to hear the difference.

My first attempt was an arm pod made from glued MDF layers! I believe Halcro used a can of some vegetable!

What I am trying to say is from my experience you will know right away whether you like what you hear or not - It is that evident. Then you will know whether you want to pursue this further. Having a hard time understanding the reluctance to try it ? Are you concerned you might like the sound?

Not sure if everyone feels this way - but - To me in this hobby nothing is more satisfying than when you come upon something - a component, a process, some setup change - whatever - that makes such a big difference to your system – that it is almost like a revelation to your listening. I have spent days moving speakers around. My floor looks like a police scene with the tape markings. This experiment took the weight of that plinth off my shoulders. It now sits in another room and my wife is asking me what is going on since I disappeared for weeks when I was involved with it. I am wondering too.

I find it ironic that most of these moments for me did not equate to a lot of money having to be spent.
How many have re-positioned speakers after having them in the same place for years. It was enlightning. This might be like that.

I don’t see the need for a debate or dispute here at all – if you are passionate enough to discuss it you should try it.

Cheers Chris

Well said Chris.
Couldn't agree more.

Regards
Henry

Dear Dertonearm,
I, like many others here, am not quite sure what you mean by the force vector diagram?
I assume that you mean a diagram of all the forces inherent in the turntable but split into parts.....plinth/platter/cartridge/tonearm/armpod/plinth?
If so, I assume you want a complete circuit whereby all the forces 'balance out' diagrammatically resulting in 'Nil'?

I have a problem with this model (apart from Raul's point that it won't tell us anything about the sound) in that it takes the accepted paradigm with a 'plinth' being part of the equation and the 'armpod' being related to this 'plinth'?

When you state that

With the "nude" TT the surface/corpus underneath the motor and the armbase IS in fact the plinth and does act as one.

I also assume that you mean either the shelf or stand or even the floor acts as the defacto plinth?

The 'Copernican' view in my Posting does not accept this standard paradigm.
It does not accept that the force vector diagram be a circuit in the terms that you are proposing.

I believe that in the case of magnetically elevated platters, the diagram is forced into a disconnect although you may argue that the guiding ceramic spindle completes the vector diagram despite the fact that it transmits no load?

To avoid this argument, imagine if you will, an entire DD turntable (with plinth if you like), magnetically elevated above a shelf.
I can imagine it so it's logically possible?
Now imagine my rigidly held, isolated armpod fixed to the shelf so that the geometrical relationships with the elevated turntable/platter remain correct and immovable.
I believe that we then approach your "platter floating in outer space" analogy and I'm not sure that your Force Vector diagram completes itself unless through the magnetic field itself.....which I suppose is possible?

At any rate, as you say on many occasions, I'm happy for you to believe what you like and I'm sure my thought is reciprocated :-)

Cheers
Henry

Dear Ct0157,
Maybe some day I will find time to test the Denon without its plinth. Right now there are at least 3 major home audio projects that come first. I am a DIYer, and I have been extensively revising the circuits in my huge Atma-sphere monoblocks. This has already taken months, since I am very anal about making the necessary decisions. It will take at least 2 months more. Then I intend to install a new attenuator in my MP1 preamp. Then I may build an LCR phono stage dedicated to MM cartridges that we have been discussing. In the spaces of time between these projects, I have all those MM and MI cartridges to evaluate in all those tonearms I now own. Once I have a handle on that, THEN I might even think about trying the no-plinth idea, but I have no clue how I would mount the Denon in space, and to make an arm pod....sheesh! I am just as smug as you no-plinthers; I like what I have, and while I enjoy this discussion, I really don't buy any of the arguments thus far put forward in favor of no plinth and especially in favor of independently mounted outboard arm pods. (And as either Syntax or DT wrote, no one is really talking about no plinth, because absence of a surround still leaves you with a casing or something around the motor and drive assembly.) The only thing I WILL say, and I am rather tired of repeating it, is that obviously there are such things as "bad" plinths. I have heard two such. I can readily believe that no plinth may sound better than a bad plinth. But I think possibly the attraction of no plinth is primarily that it may introduce euphonic colorations that are ablated with a really good plinth that can render the turntable "neutral". (Of course, one man's neutral is another man's "lifeless".) And the beat goes on.

By the way, I certainly don't think I have "vast experience". Thanks for the compliment (assuming it was not facetious), but for most of my 35-year audiophile career, I owned only one tt, one tonearm, one cartridge at any one time. I am into this multi-everything craziness for only 2-3 years. Audiogon has been my undoing.