A Copernican View of the Turntable System

Pardon my arriving late in this discussion.

If I can weigh in on something for a moment? I think Dertonarm and I are in agreement here: the coupling between the base of the arm and the platter of the 'table must be exact and profound. To that end, there can be no play anywhere, with the plinth being both rigid and non-resonant.

If the arm is mounted on a separate 'island', it will be impossible to reproduce the LP exactly, as any differences between the platter surface and the arm base, for example microscopic vibration or resonance, will be interpreted as coloration by the reproducer.

The system of platter surface, bearing, plinth coupling to the arm, the arm and finally the cartridge can be likened to the steering and suspension of a fine motorbike or automobile. Any slop or flex in such results in handling problems!

So quite obviously a plinth that has resonance and/or is not perfectly rigid, an arm with slop in the bearings, an arm without a rigid, resonance-free arm tube, a platter with resonance and a platter bearing with slop will all contribute to coloration in the playback.

Raul, yes, obviously if one boat is the LP and the other boat is the base of the arm, the motion between will be heard.

Absolute rigidity between the LP surface and the cartridge body is paramount! That requires no slop in the arm or platter bearings, and that the platter, plinth and arm tube are both rigid and acoustically dead.

Rauliruegas, in your prior post I am afraid that you lost me. I can't really make out what it is that you are trying to say.

Y'all realize that by going 'nude', that the platform has become your plinth, right? The same rules apply.

Now if the original plinth has problems, is not acoustically 'dead', IOW has a resonant signature, it may well sound better to switch things up.

I think you will find that the mounting for the platter and the tower for the arm will sound their best when coupled as tightly to the non-resonant platform upon which the resulting turntable is being constructed.

Rauliruegas, OK let's go with that for a moment. You hang it from the ceiling- where is the tonearm? Hanging also? On a separate string? Obviously *that* is not going to work...

So, you have to connect them together somehow so the sacred geometry is maintained. And that is just so tracking errors are minimized. So how are you going to do that?? A platform? Now the signature of the platform is the signature of the system. You could use some sort of bar or strut to hold things, again, any signature in them will be heard.

So the model does not seem to hold up.

Halcro, points are a sort of mechanical one-way diode. That is they are fairly efficient at transmitting vibration in only one direction. So if your points are pointed *down* under your tone arm: welcome to your plinth, the anti-vibration platform.

Any good anti-vibration platform will have both 'acoustically dead' and 'absolutely rigid' as a mantra.

I agree that a bad plinth is likely worse than none. I've been down this path before- my turntable has been in development since the early 1990s. So the comments I've been making are based out of experience, not conjecture.

If you want to separate something, and if the 'table is not a direct-drive, then the motor might be a better candidate. However IME the vibration of the motor will be of no significance if the plinth works right.

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.

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.

Halcro, the Empire is equipped with a belt, and an extremely robust drive motor, one that is just about unstoppable. The speed of this machine is so stable that the usual effects of soundstage drift due to speed variation don't seem to exist- its soundstage is a lot like that of reel to reel.

I am of the opinion that a robust drive is what is important, more so than the *type* of drive. If it is wimpy it will not matter what kind of drive it is!

As a result, if you look at vintage turntables, you will see a following around certain models that were better at getting things right than their competition. All of these machines have very robust drive systems too- the Empire, the Garrard 301, the Technics SP-10.

I think this topic was covered elsewhere.

Dgob, any resonance in the arm tower will be a coloration. If the feet prevent the tower from coupling to the base of the platter bearing, that too will be a coloration.

At low volume levels its not that hard to get a 'table to sound good. Its at high volumes where the rubber hits the road. IMO, the turntable should be unassailable at any volume. I found that once I had sufficient mass and rigidity in the plinth, that that helped, but I also have the 'table perched on an Ultra Resolution Technologies platform, which is one of the best passive platforms I have seen, unfortunately no longer available (and stupidly expensive when they were!).

The platform is in turn set up on a Sound Anchors stand that is custom-built to accommodate the platform. In turn the stand is mounted on 3 Aurios-Pro bearings.

My point is that it is hard to really know what is the plinth in all this. The only decoupling that occurs is the platform itself and then between the platform and the stand, that is my 'suspension' so to speak. The platform is quite heavy, rigid and inert as it is a sandwich of a special grade of marble, high tensile steel and a military-grade constrained damping layer.

Vibration and resonance can be quite insidious in a turntable, so with respect to the anti-vibration platform, the platter and now (in the case of this thread) the arm tower, it is likely that it would be really difficult to go overboard on the whole thing.

Points in use under the platter and arm tower, while being mechanical diodes so to speak, are not actually perfect diodes. Like elastomerics, they are more efficient if they are loaded properly! So if the load on them is underpar, they simply will not work so well. Load up that arm tower! Get some mass on it, so the points can do their job.

Dgob, all elastomerics have a range of operation- a minimum loading and a maximum. Depending on where you get the elastomerics you can often get a datasheet that can be very helpful in this regard.

However, I did increase the weight of the armtower to over 6kg and this brought no major improvements - save stabilizing the imaging.

In my book, stabilizing the imaging is a major improvement! One of the weaknesses many 'tables have relative to analog tape is image stability. I really could not get my 'table to do that as well as tape until I installed the solid plinth (damping the original plinth, which was hollow-cast, was not enough!).

'viscoelastic platform'?? What's *that*?

viscoelastic doesn't sound like something you want to use as a plinth, although if you do have a rigid plinth already such a material might be good for damping.

Dgob, So how do you have things set up now? What is the arm tower sitting on?

It seems that in a live performance one is very rarely (if ever) as acoustically aware of space between musicians or their three dimensionality. My suspicion is that hifi compensates for the visual stimuli that is provided in a live performance with the over emphasis of these audible features. Small ensemble acoustic or vocal performances might be the occasional exceptions to this.

Its been my impression that there are several things that can contribute to this- how a recording is made (many are un-natural) and how well its details are reproduced. For this subject though, let's throw out the un-natural recordings, at least for now.

What I have have found is that as a system looses the ability to reproduce low level detail (and consequently ambient information) the result is that the musicians in the ensemble tend to have a quality if a cardboard facsimile rather than the real person. So spaces between the instruments are larger, making the individual instruments seem to be in greater relief.

Now as the system attains greater ability to reproduce ambient information, that information tends to flesh out the performers and fill the spaces in between. This causes the soundstage to *seem* less distinct, until one realizes how much more reflection information is being reproduced!

Of course in a real music situation, the ambient information is seamless with the instruments themselves, but I think a lot has to do with the space in which the music occurs. Having done a lot of recording and listening in such spaces locally, I don't think I can agree with the comments in quotes, at least with the recordings I have heard- I hear the imaging information quite easily in those rooms and halls, whether live or recorded!

The Herzan has been integrated in my system for 6 months now, and not only is it the final 'piece' of the jigsaw for the 'Copernican' puzzle.....but it singularly is the most significant contributor to the elimination of 'distortions' and the elevation of sound quality that I have experienced in 40 years of audio.

That is because it is effectively acting as the plinth. The arm is now rigidly coupled to the platter, which is as it should be.

@fsonicsmith  +1

@halcro 

Hi Ralph,
I've noticed that both you and J.Carr have recently 'transferred' over to 'The Dark Side' by adopting the new Technics SL1200 DD turntable over your previously loved belt-drives.
The Empire in your case and the Final Labs and big Micro Seiki in Jonathan's.
Can you reveal why you have changed, and what the Technics does that the Empire doesn't?

Actually I still run the Atma-Sphere model 208 (which looks for all the world like an Empire 208 but uses an entirely different plinth).

However I also have a lot of respect for the Technics SL-1200G. We had one here in the shop recently; a customer wanted to install a 12" Triplanar on it and wanted to know if that was possible. It was.

I took the machine entirely apart and since I've had a lot of experience servicing consumer electronics in the last 45 years, I was very familier with the older SL-1200s. The new machine looks the part, but is an entirely new design with many improvements.

One improvement that impressed me was how much attention was paid to rigidity of the plinth, while at the same time applying five different damping systems! In addition, the speed stability is one of the very best in the world, being second to only the SP-10MkIII. Its a very impressive machine and anyone serious about high end audio and wanting a turntable should consider it.