Eminent Technology ET-2 Tonearm Owners

Dgarretson
Dover, can you clarify a few points concerning the effective horizontal mass of ET? The manual states that it is 25-35gms. Is this the mass of the wand plus manifold tube, which is then increased by addition of up to 40gms in counterweights?

Hi Dave
Page 5 of manual – spindle weight (14 grams) tonearm tube weight (11 gms) plus the counterweights. To give you a reference point I am using one large and one small counterweight with the 420 str. That should be 20 gms.

Page 9
‘By decoupling the counterweights horizontally but not vertically, the mass of the counterweight is not seen by the cartridge above a certain frequency and is lowered. This allows use of heavier (more rigid) components in tonearm design with increasing effective mass. Decoupling mechanism is damped at a 2 – 5hz.”

Maybe Dover, Richard or others can add more regarding the horizontal inertia.

"lots of variables"

YUP :^)

Cheers

but I hear a slight negative which does not exist with the mass approach. As I said, I think that it is caused by induced currents circulating the spindle.

Hi Richard - Did you try the magnetic damping on belt drive or string drive as well ?

Do you really want these currents anywhere near your delicate feed from the cartridge?

Richard – in your opinion what would you consider as “near your delicate feed”. Reason I ask.

The two little circle magnets I use with my ET 2.5 - the closest one is a good 7 or 8 inches away from where the wire exits the armtube – when at the the end of the record which is the worst case.

I should note I am using copper on the ET 2.5 right now. I have silver on the ET 2.0 that is on a brass armpod. No room for trying magnets there.

Looking at my analog gear its obvious I am not afraid of magnets.

I know some who think magnets cause cancer.

Can you give some details on how to go about making that lead slug for inside the spindle?

Cheers Chris

Chris.

While I have built a number of BD turntables, they all employed pivoted arms.

The eddy currents induced by the magnet are everywhere within the spindle since it is conductive, so having the magnets at the opposite end to the wand does not take them any further away from the cartridge signal. Therefore it is "near". The negative effect was apparent before and after I changed the goose neck to conductive aluminuium.

I made the internal slug by rolling up 1/2mm thick lead sheet strips. Cut to different widths. The roll OD was equal to just less than the ID of the spindle. Different widths gave me the ability to experiment with different weights.
A string was passed thru the center of this roll and thru 1/4" plastic tubes like that used for the air feed. String tied off one end and a length left at the other. The tubes were cut to length such that one tube protruded a few mm once the tube/lead/tube assembly was slid inside the spindle. Thus when the counter weight end cap was reinstalled it slightly compressed the tubes. Tubes were equal length to position the lead in the centre of the spindle. The pull string allowed the whole assembly to be removed.

Everything causes cancer.

Chris
My apologies if this has already been covered in the thread, but can you tell us the sonic differences between the ET2 and ET2.5

Many thanks

Richard, My ET 2.0 versus the ET 2.5 – both have high pressure manifolds.

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. Bruce built it a few years ago for me. It was designed to run at 19 psi. Unlike my ET 2.0 which will run at 19psi and a low 3 psi as well, my ET 2.5 will start binding up if I drop the pressure – not sure what the actual PSI number is. The spindle starts resonating above a certain psi. We have discussed this here before. The consensus seems to be this PSI number varies just like our individual setups. For me its 19 psi and the reason I had the arm made for that psi.

Richard as far as sonic differences with me.

Let me use an analogy. We have all seen those graphs that show motor oil and the difference between lets say 5w30 and 10w30 motor oil at different temperatures.

http://i36.photobucket.com/albums/e29/2002neonrt/35graph.jpg

Lets assume lower temperature represents lower compliance / heavier cartridges – that is the ET 2.5 5w30 and the ET 2.0 is 10w30. Both overlap and work well within a large range for both MM and MC. But when the setup is tweaked/improved I think the ET 2.0 works a tad better with MM and ET 2.5 with MC. Does that analogy make any sense?

People assume the ET 2.5 is better because it is (.5) the next newer version. It depends. It came after so the obviously the parts themselves are newer but as far as sonics go ? well we know the smaller diameter 2.0 spindle according to Bruce resonates at 5-6 hz. The 2.5 resonates at 2-3 hz.

The armtubes are the same as far as I know for both versions. Aluminum original one better with higher compliance, CF – middle ground – Magnesium – for really low compliance. This is the advice from Bruce with the testing he has done.

The ET 2.5 sucks more air – has more volume. When they were in the same room I remember how the pressure gauge when I unplugged one for other would move by a few PSI. Ketchup’s graph shows this too.

The ET 2.0 was around when vinyl was in its heyday along with MM cartridges. Then came MC cartridges and BT adjusted (I guess) to the time and introduced the 2.5 with its lower resonance. Just an opinion.

If all things were the same – apples to apples - We know that will never happen.

The ET 2.0 seems to handle a little better with lighter higher compliance MM’s. Like a lighter sportscar with great handling. But add a bigger motor to the sportscar (heavier MC/stiffer/lower compliance ) and I feel the ET 2.5 handles a little better. Bigger diameter spindle along with the lower resonance. A very rigid spindle to manifold coupling in my 2.5.

The differences are not day and night. The MM 420str sounds great on the 2.5. Its just seems to be a little more ease on the 2.0. Bruce’s review of the 420str kind of confirmed this to me too.

So I use MC on my 2.5 and MM on the 2.0. The rooms are adjacent to one another in the basement.

Hope that helps.

Richard you mentioned that you studied the Dynavector arm. Did you take any measurements of it - Impressions ?

Cheers