A Copernican View of the Turntable System

By the way, in the real world there is no such thing as "complete (mechanical) isolation", which is why I take the position that I take.

So when someone claims to have built an 'acoustically dead' plinth, claims of death are exaggerated? Or what does that phrase mean? Really, I don't know. Is it something separate from isolation?

If one can create an acoustically dead plinth for one's turntable (as a whole), then mutatis mutandis why couldn't one create separate acoustically dead plinths for TT chassis and tonearm? Does that mitigate the concerns regarding coupling? Or is that a method for coupling?

Too many concepts; too little knowledge (on my part).

Banquo,
The point of weighing down the armpod is to couple it to the surface below (which in turn should couple it better to the TT). Putting separate AT616s under the table and the armpod separately negates the effect of adding on the weight to the armpod. At least in the SNL case the rabbi and baby were 'coupled' to the same backseat. Your proposed method suggests the rabbi is better off leaning through a window of another car alongside. If it were me (and it is not), I would suggest putting all four footers below a rigid layer to which both TT and pod are coupled.

Your method may work in practice, but it will limit the improvement you get and increase distortion in other ways. First, if you put ONLY the TT on 616s and leave the armpod spiked, AND that is an improvement, it indicates the footers worked. If only the armpod was on footers, and the table were not, and that also improved things, either you have a separate component-led problem to the first one or you have the same problem of resonance coming into everything from below. If your tonearm is resonating, you need to fixt that separately. If it is resonance from below, you want your tonearm and table on the same decoupling platform or the different load presented by armpod and table vis-a-vis their respective isolations will cause weird distortions.

@Chris: how did you put spikes beneath your sp10? I'm assuming there's a board in between? That is, the TT sits on the board and the board is on spikes? Or did you thread spikes directly beneath the chassis?

Hi Banquo - Each of the mapleshade footers have a dimple on top. I am using the bottom half of a two piece system. I put a dab of blue tac on the dimple.

The blue tac after setting in overnight is not going anywhere. For me to remove the footers now requires considerable force. You have to pry them off. So no threading was required.

I have a picture of the mapleshade footers in this link.

http://www.canuckaudiomart.com/view_userimages.php?user_id=5181&image_id=40437

Putting another board between the sp10 defeats the purpose of this to me. It adds one more layer and one more chance of introducing resonance going up to the platter and down.

My armboard although not pretty to look at is very functional and will not move. It also holds the bracket that the tonearm cables are connected to.

There's really no such thing as the complete absence of a plinth. In a typical DD table, the motor is often mounted to a chassis, usually an aluminum enclosure, like the SP10 or Halcro's TT81. And to me that's a plinth already.

The best experiment, I think, is take the motor out and place it bare naked on a platform, perhaps supported by tip-toes and might need to be held down by something (which can open another can of worms) because the start-up torque might jerk the the motor out of placement in relationship to the tonearm geometry, unless the casing for the motor is really hefty. Essentially, a comparison between yes-chassis and no-chassis. Naked motor and not so naked motor. Anyone wanna try that?

If the naked motor sounds better, then a NO-PLINTHER can wear his/her t-shirt proud.

____

T_bone,

I suspect the weight will be the issue and I am in the process of addressing this.

About the potential effects of this: I am deliberatley aiming to de-couple tt from arm tower. That in short is my experiment and is not (from my limited understanding) adverse to meeting the basic laws of scientific proof. Also, and given the basis to this exercise, I really do not see that by coupling the arm tower to both the Symposium Ultra and its supporting wall shelf in any way "negates the effect of adding on the weight to the armpod."

I think that Chris and Atmasphere have already suggested the potential for varied approaches to 'isolation' and to 'damping'. Beyond that, I can only reiterate that the gains already achieved by decoupling the tt (in a manner that I know you appreciate equally) has proven as huge a success as we have previously discussed. The question (and basis to my experiment) is whether further gains are to be had though the method of damping an isolated arm tower. The isolation point seems to me proven in my initial blue tac approach and the results that I obtained there. The damping of the arm tower is where my attention currently lies. To wit, weight.

I can offer no greater certainties than that and the obvious results already obtained at this early stage.