Eminent Technology ET-2 Tonearm Owners

I'm bowing out, while whatever I offered, maybe, somewhat remembered. ( for what, that is for you to determine) Good luck to you all! .... remember the dragonplate... I'm not associated...>

Ketchup
Yes your shim idea is a good one. I wonder if it would be possible to fashion tiny wedge shaped shims and push them in. Could maybe eliminate a bunch of trial and error with individual parallel shims.
And yes I agree, there is considerable compliance in the orings. Also in the original goose neck and arm pillar/ manifold interface.
Chris, yes I have the CAD CAM machines that could make the goose neck and a complete arm. ( excluding spindle and sleeve. ) It would however be costly due to the likely small runs.
The original Counter weight mechanism has been discarded. Adjustment is by means of two knurled discs, either side of the weight, on a M10 threaded rod. You can kinda see this in one of the pics Ketchup found.

Ref horizontal mass, I realize that this is controversial. I simply encourage those of you who feel the urge to try it. Particularly those of you that have full range systems. ( response into the lower 20s )
If we redefine horizontal effective mass as resistance to lateral acceleration we will see that magnetic and oil dampening are similar to " pure mass" all three options resist lateral movement and all three increase this resistance as the lateral movement increases in frequency.
All three impose lateral forces on the cantilever when the record hole is not centered.
The reason that I believe that the rules for horizontal effective mass are different for pivoted and linear arms is this.....
With a pivoted arm the horizontal effective mass in multiplied by the head shell offset. Only a percentage of the cantilevers lateral movement is resisted by the arms horizontal mass in trying to rotate the arm the rest of this movement is resisted by the cantilevers efforts trying to bend the arm tube itself. Linear arms do not impose the second characteristic on the cantilever. This I believe is one reason that the pivoted arm guys complain about a lack of gestalt from linear arms. We largely fix that with oil troughs or magnets. Pure mass is another option

Lead is strategically placed in an ascending hierarchy throughout the arm and TT itself. Tests with a number of soft and hard materials in the head shell and elsewhere convinced me that "local" sinks are beneficial.

While the magnetic dampening was an improvement over the oil trough, it was not as good as the recently added lead slug. It is speculation on my part why this is, but the induced currents seem to be a logical possibility. If they do exist, I suspect that they would be AF in nature, not RF.
I heard this, admittedly, small problem with the original arm wiring, OFC Litz headphone wire I then used and with the silver I now use.
Twisted pairs of wires are less susceptible to RF due to common mode rejection.

In my TT, the arm and motor are rigidly fixed to the same upper acrylic layer.

Dover, are you still running an ET2?

Richardkrebs
With a pivoted arm the horizontal effective mass in multiplied by the head shell offset. Only a percentage of the cantilevers lateral movement is resisted by the arms horizontal mass in trying to rotate the arm the rest of this movement is resisted by the cantilevers efforts trying to bend the arm tube itself. Linear arms do not impose the second characteristic on the cantilever. This I believe is one reason that the pivoted arm guys complain about a lack of gestalt from linear arms. We largely fix that with oil troughs or magnets. Pure mass is another option

Hi Richard – Have you actually measured these forces? I find it very interesting that what you say is supported by information I have from BT on actual testing that he has done with pivot and linear arms. His measurements found that this phenomena (horizontal effective mass, multiplied by the head shell offset and the resulting bending of the cantilever) produced a +6 to 12dB bump between 10-15 Hz versus flat response down to 5Hz (the ET-2).

He also went on to say that “over the years these parameters have been mathematically analyzed and are well understood. There is an easy measurement to prove all of the above, it is called is wow and flutter. If you take the same turntable, put a straight line tonearm arm on it and a pivoted tonearm, both with the same cartridge, the straight line arm will exhibit about half the measured wow and flutter.”

I have his summary findings on this if anyone is interested. Alot of his findings again are in his ET2 manual available publicly.

Some of it was posted here already
here already.

Richard, Dover others ...... any comments on this very basic wow and flutter test ?

Hi Chris - yes I agree with Thigpens comments, but I think Richardkrebs high mass approach throws away the advantage of the ET2 over other tangential arms, that is the light horizontal mass. The ET2 is less than 25gm compared to the 80g of the Terminator. The effective horizontal mass of the ET2 is even lower with a decoupled counterweight. The other problem with adding mass to the ET2 is that not all low compliance cartridges are created equal, as the compliance in the horizontal plane cannot be assumed to be the same. For example the Denon 103 is far more rigid in the horizontal mode than the Koetsu even though they are similar compliance vertically.

Chris.

No I have not measured these forces and would be very interested to read Bruce's comments on same. I assume it is a big file, so can I ask you to email it to me at the contact address on my web page, if not too much trouble. Or if appropriate post it here.

As per my earlier post, both an oil trough and a magnet impose a resistance to lateral movement as seen by the cantilever. They behave much like weight in the lateral plane. I have simply used weight alone.

I did my initial tests on extra horozontal mass by disabelling the leaf springs on the counterweight beam and winding equal lengths of solder around the goose neck and counterweight assembly. This way I kept the lateral balance of the arm static. It didn't look pretty but was informative. I also tried this configuration with and without magnets.

I currently adjust for different cartridge compliances by using a range of counterweights.

Dover, I seem to remember from this thread or another that you no longer use an ET2. If so, we would be intereted in what you are currently using and any reasons for the change. As we all, I think, agree, the ET2 is pretty darn hard to beat.