Eminent Technology ET-2 Tonearm Owners

First an observation as I read what Ketchup and yourself said about the compliance in the air bearing spindle.

Ketchup do you notice any difference in force required to move the spindle in your ET 2.0 and ET 2.5 with no air on?
My ET 2.0 spindle can be forced through the manifold with no air. There is quite a bit of resistance but it can be done. This is normal according to Bruce. And its anodized coating prevents any damage.

My ET 2.5 spindle will not move – it is really tight. There is not much movement at all without air. It has to be really forced.

Chris,

The compliance that Richard and I were talking about was in the o-rings between the manifold and the manifold housing. No matter how much air pressure you can get between the manifold and the spindle (making it very rigid), you will always have the squishy o-rings causing the spindle and manifold to move within the manifold housing. Not rigid = not good, hence the shims. Most other linear tracking, air bearing tonearms don't have o-rings to soften up the bearing. I believe that getting rid of this compliance may have a huge effect on performance as Richard suggested. I WILL be doing this after I get my system set up and I'm familiar with the sound without the shims.

When I bought my ET-2.5 arm I actually did notice that it was a little difficult to move in the spindle with no air. I assumed that the spindle was out of round, but it worked fine with 1 psi in it when I did the air flow tests.

Looking back at my notes from the air flow tests, I observed dragging at 1 psi with the ET-2 (set up on a TT with the arm wand, cartridge, and counterweight) but did not experience dragging with the ET-2.5 at 1 psi. The ET-2.5 setup did not have an arm wand or counterweight attached, though, so it's apples to oranges. The dragging with the ET-2 was most likely due to the added weight of the arm wand, cart., and counterweight.

Also, I showed Bruce the results of my air flow tests and he said that both my ET-2 and ET-2.5 tonearms were set up for high pressure. I should have mentioned this earlier...

Thanks for your post. j

A real interesting read for me the last couple of days. Ketchup please keep us updated on those shims and I hope you get "one" of your arms up and running soon. Yes I was referring to the compliance between the “spindle and manifold” only. Sarcher30, John47 welcome to the thread.

Excellent video link Ketchup.

The ET2 tonearm no magnetic parts to be found anywhere on the tonearm itself. Put a magnet to it and find out for yourself. The cartridge itself, well don’t put a magnet there.....how close is ok or is it ? It got me curious. I hate unknowns.

I have been reading both Richard and Dover’s positions on it. Have learned alot. I have something to share regarding these magnets, magnetism and it has to do with my Dynavector tonearm.
I took one of the small circle magnets from the ET2.5 setup over to my Dynavector tonearm. What followed kind of reminded me of one of those horror movies –you know the one where the guy wakes up and finds himself magnetized in a kitchen; pots and pans, knives start flying towards him getting stuck on him as he ducks.

ok - no pots and pans or knives here. But I did LOSE the magnet as it flew out of my hand. I had to search to find where it had lodged itself. Under one of the magnetic dampers near the DV505 base is where I found it. There is a little bolt (magnetic) on the left side of the main arm (as it has two arms). This is not shown on the tonearm diagram. Its helps with antiskating. As you get a few inches away from the post where the arm rests, the current draw is noticeable. The cartridge itself is about 6 inches away from this position which seems to be the last spot where a magnet field exists. On my ET2 arm the actual cartridge position because of it design is much further away.

This got me curious so I sent an email to Masaaki at Dynavector asking about these magnetic levels. I’d like to say that Masaaki has to be one of the friendliest and knowledgeable audio people I have come across over the years in this hobby. Always responsive to my questions. I asked him for information about the “magnet force” levels on the Dynavector tonearm.
His response.

Hello Chris,

Unfortunately we cannot publish data of measured magnet current levels used the flux damper magnet in the DV505 tonearm. Only information is that the Magnetic flux density was multi-thousand gauss.
Thank you and best regards,
Masaaki
Dynavector

Multi – thousand gauss ? what does that mean ?

Gauss Unit/Levels
• 10−9–10−8 gauss – the magnetic field of the human brain
• 0.31–0.58 gauss – the Earth's magnetic field at its surface
• 25 gauss – the Earth's magnetic field in its core[3]
• 50 gauss – a typical refrigerator magnet
• 100 gauss – a small iron magnet
• 2000 gauss – a small neodymium-iron-boron (NIB) magnet
• 600-70,000 gauss – a medical magnetic resonance imaging machine
• 1012–1013 gauss – the surface of a neutron star[4]
• 4×1013 gauss – the quantum electrodynamic threshold
• 1015 gauss – the magnetic field of some newly created magnetars[5]
• 1017 gauss – the upper limit to neutron star magnetism; no known object in the universe can generate a stronger magnetic field[5]

I am trying to figure out why Dynavector would use Gauss levels in the multi thousand range? Would they not have measured its affect on the phono signal ?

From the DV505 manual - similar info to the previous posts.

electro magnetic damper
This damper applies effect of eddy current, which is generated when conductor moves in magnetic field, and which obstructs conductor in motion. It has almost no damping effect on motion of non-vibrating tone arm, but is highly effective to vibration of arm, such as arm resonance.

DV505 Manual

Richard – can you tell us what type of magnetic damping you experimented with that led to your opinion of it? Position of the magnets relative to the arm, Gauss levels ?

Dover - I believe you were using a fridge magnet ? which is about a gauss level of 50?

Cheers

Gentlemen, fantastic and very interesting reading over the last few days; thank you.

Dover, I want to try magnetic dampening. Could you please provide some more details about the positioning of the magnet for your magnetic dampening tweak? Did you place it between the manifold housing and the front edge of the tt, or between the manifold and the rear of the tt? Also, how did you orient the magnet's polarity? Does it matter?

Ketchup, I am intrigued by your idea of shims replacing the O rings in order to increase the rigidity of the bearing. I am confused however. Don't the O rings need to remain in place in order to keep air from leaking out of the manifold? What type of shim are you referring to, that is both very rigid and will seal the outer diameter of the manifold to the housing? Are you suggesting to place shims inside the manifold housing, between the OD of the manifold and the ID of the housing?

Chris, thanks again for starting what is currently, and without a doubt, the most interesting thread on the subject of LP playback on the 'Gon; IMHO.

Slaw, if you're still out there: what happened?

Regards to all

Ketchup, I am intrigued by your idea of shims replacing the O rings in order to increase the rigidity of the bearing. I am confused however. Don't the O rings need to remain in place in order to keep air from leaking out of the manifold? What type of shim are you referring to, that is both very rigid and will seal the outer diameter of the manifold to the housing? Are you suggesting to place shims inside the manifold housing, between the OD of the manifold and the ID of the housing?

Frogman,
The shims will not replace the o-rings- they will be added to a completely stock, unmodified arm. The way the arm is built, there is about 3/16" of "free space" between the manifold and manifold housing before the o-rings. To illustrate what I mean: Cut a piece of paper into a thin strip 1/8" wide and an inch long. Slide the piece of paper into the gap between the manifold housing and the manifold. It should slide in about 3/16" before it hits the o-ring. That space is where the shims will go. Here's a photo of my ET-2.5 manifold that shows the 3/16" gap:

ET-2.5 manifold

I like Richard's idea of making them tapered, but my OCD will have me constantly worrying that they have moved. A good compromise would be to make two of them non-tapered and make the third one tapered to apply the necessary force to lock the manifold in place. A small dab of silicone should hold the tapered shim in place and will be completely reversible.