Tonearm mount to the plinth vs arm board vs rotating arm board vs isolated tower

@halcro 

And for the record, I never made a statement like that. One way you can tell this is so is that I don't use emojis in any of my posts. Putting up a post like this is oxymoronic; the post is false in every way.


Look, rather than kill the messenger, why not look into the physics involved? Credibility is not gained by never admitting a mistake, its gained by acknowledging the miss-step when real and correcting it.

Yes, it works fine. Bob Worzella of Sound Anchors mentioned this to me about 30 years ago- this is how he was able to prove that his stands for Vandersteens actually resulted in better measurable performance.

@halcro 

a turntable that struts and frets its hour upon the stage, and then is heard no more: it is a tale told by youtube, full of sound and fury, signifying nothing.

I heartily recommend that everyone make their own recordings in high fidelity. A nice tape machine and a good set of microphones are required. Find a nice-sounding venue and make a recording of something that you can stand to listen to over and over. Then have it mastered and pressed onto LP. A test is fine- you don't have to make a full run.

At least then you have a reference; you were there, you have the master tapes, you know what it sounds like.

Or you could use a mirror mounted on the item under test, a laser and a sound source to demonstrate how a separate arm pod will not vibrate the same as the plinth onto which the platter is mounted, even if both use the same construction techniques!


In the case of the first you have a subjective means to winnowing out how a separate arm pod is a failed concept; in the latter you have a means of measuring it.


I do agree with Halcro on one thing:

What I DIDN'T appreciate at the time....was that the same principle of weight/mass applies to the TURNTABLE PLINTH 🥴

A plinth that has low mass can't also be rigid and dead (IOW damped with no ringing). In this it appears that Halcro has realized that some of what I've said is true- so my challenge to him is to go ahead and finish the job- build a plinth that has the weight and mass, that is 'dead' and provides a means of mounting the arm **directly** to it. So far what I've seen of his efforts appear artistically wonderful, but lack a bit of science. If you're going to go through all that work, why not try both principles? Of course the same construction techniques should be used so as to minimize variables, otherwise its apples and oranges!

This was covered in detail on the Copernican thread.

I remember something about that. If the devices (such as the arm pod or the base of the platter system) use isomerics or the like between them and the plinth that **will** result in coloration. If carefully hard-coupled to the plinth the coloration is reduced. But using an arm pod is problematic as its likely that it will not be perfectly rigid and dead as the application requires.

Have you guys ever seen Halcro’s photos of the interior of his Halcro preamplifier? Something like that in black.

Yes- we donated one of our Atma-Sphere model 208 turntables to the local audiophile society and someone there used a 'paint' like that on it. It was kindof unnecessary, you can walk up to the platter and thwock it with your forefinger tensioned by your thumb and not hear it in the speakers.


You might be able to get good results with a separate arm pod, but you will get better results if the arm mounting isn't separate from the plinth.

There are anti-vibration extensional compounds that are applied similar to paint.

I agree with @halcro , it is essential to isolate the tonearm from the platter bearing and the motor.

This opens the turntable to colorations. Apparently Thorens has this sorted out:

The idea if I understood Greg correctly is that everything vibrating is concert is better than vibrating out of synch.

This is why the tonearm must be rigidly coupled to the platter bearing, and hopefully the surface of the platter as a result.

Here is the engineering principle that must be observed when designing a plinth for a turntable:

The plinth must be as rigid and as acoustically dead (damped) as possible. The mounting of the platter bearing in the plinth will be thus coupled as rigidly as possible to the mounting of the tonearm. If it is not, any vibration at all can be interpreted by the pickup (arm and cartridge) as a coloration.

IOW, if the arm and surface of the platter are able to vibrate at all, if they are always in the same plane of vibration, the pickup will not be able to pickup noise or coloration on that account. So a separate arm tower is a violation of this principle and induces coloration;  the same is true of a separate arm board. If the arm board employs damping and the plinth does not you'll get a coloration. It all simply has to be as rigid as possible and damped.