A Copernican View of the Turntable System

Halcro, here is our 'table. We've been making it about 10 years. It looks all the part of an Empire, but looks can be deceiving. The photo is from about 2000 or 2001.

http://www.atma-sphere.com/products/208.html

Dgob, I have a little thought experiment for you. You have the platter on its stand or whatever, and you have the separate arm tower. But we are going to put a vibrator under the arm tower but not the platter, and run it. The question is, will you be able to hear the result? I think you can.

That, in a nutshell, is what the issue is. There simply can be no extraneous motion besides that of the arm tracking the LP! **Any** other motion is a coloration. So if the arm tower is able to vibrate or resonate at any slight amount that is different from the platter, you have coloration. Cheesy plinths totally allow for this sort of thing- that is what I have seen over and over- and so getting rid of a cheesy plinth is likely a good idea.

But that is simply not the same as having a plinth that is properly engineered! (This is sort of the same argument that because a particular LP is scratched and warped, therefore all CDs are better than all LPs.) And you are experiencing a step towards that, as your platform for your towers is in fact your plinth. Try coupling the platter and the arm more tightly into that platform and see what happens. The more dead you can make the platform, the stiffer you make it, the better the 'table will sound.

Atmasphere,

Thanks for sharing this. It clarifies your point well. I am still left with the issue about theory and practice though.

The Acoustic Signature Mambo shares your approach with increased mass and a rigid and directly affixed arm-column. It is simply phenomenal in its performance when well isolated. However, the seperated Technics/arm-column improves on specific areas. Key among these are the scale (depth, width and height) of the sound stage; the air/audible space that exists between performers and the ease with which the entire performance is resolved (leading to smoother sound at higher volumes).

I am still not absolutely certain what trade-offs might be happening and so I will explore this fully before determining if what I am hearing is just different or actually 'better'. One thing for certain is that it is a dramatic difference.

The questions that remain would therefore (at least for those using pneumatic devices under one component or both to decouple the arm-column/TT) seem to include to what degree and at what specific point or level do disparities in vibration of arm column/TT impair the quality of sound produced. They might also include questions of how much does appropriate VTF compensate for any such disparities. This and - 'most importantly - the obvious difference in performance that I am getting at present are important reasons why I'll continue to experiment with the phenomenon of seperation and decoupling. As part of this, I am considering trying spikes, viscoelastic and pneumatic options under the arm column itself, as I am not wholly convinced that seperation and decoupling "must" involve disparity.

Time and my hears will tell and both can only be further assisted by the kind contributions of people such as yourself.

Dgob, the problem with the Technics is that it does not have a real plinth. It is built for the platter only. If you have the deluxe base, the material that the arm sits on is something quite different from that of the platter, at least that is the case in my friend's MkII.

This use of dissimilar materials shows that there was not really a concern for the matter at the time. I would say this is one of the things in 'table theory that has advanced since the Technics was built.

So in this case, you have to come up with something- the resolution of modern systems being what it is, you can easily hear the faults in the original 'pseudo plinth' system. That is why there are some fairly ambitious plinth projects out there now for the SP-10. Its a great table, but it needs a plinth to really work.

In the case of the Technics (if you will pardon the pun) it does seem that if you can separate the platter (and ditch the original 'pseudo plinth'), pin it to a decent platform and then come up with a decent arm tower, that that would be the most expedient means of creating a proper plinth.

I've had the idea of making a massive machined metal sandwich of aluminum, brass and high grade steel, that mounted the platter and had provision for the arm. The sandwich was dissimilar metals so their resonant frequencies would be different and thus self-absorptive, while at the same time maintaining rigidity.

If there has been anything about the Technics machines that has ever struck me as goofy, the 'pseudo plinth' is it. I know its similar to a lot of radio station 'tables in that regard, but they *did* pitch it as a high-end consumer machine too.

Atmasphere,

I think what you say about the popular plinths for the Technics seems true to my experience. I know someone who used the SAEC solid metal plinth and who still swears by it. However, shipping costs for that monster from Japan are just too prohibitive: at least for me in the in the current economic climate. I think it is also made predominantly or completely from Aluminium and so there are likely to be resonance problems. However, I'm not too certain if they went along the same route as Acoustic Signature in a mixed metal approach similar to the one you have suggested.

I also agree about the most expedient approach and that is precisely (if I follow you correctly) what I and others have been trying to do. The only question is whether instead of pinning it to a platform, using the AT616 provides a suitable alternative. This leaves the question of finding a decent arm tower and the experimentation that Halcro and others seem to be undertaking seems fascinating along these lines to me. I'll try the spikes seated on some industrial absorption material and let you know how that goes.

Thanks again

Dgob,
I think it was mostly stainless steel by mass but I will try to dig up that information. I have a copy made by a metals engineer who tried to copy the SAEC plinth, and the thing has three layers of different metal with slightly different resonances. It does weigh a short ton.