Eminent Technology ET-2 Tonearm Owners

Richard and Chris, I have always had a 50' spool of excess (unnecessary; length-wise) clear and fairly rigid tubing between the pump and my surge tank. Like Chris mentioned, the coil of tubing will act as a surge tank. I was able to confirm the benefits of doing this when my previous surge tank exploded and I needed something in the interim.

I am intrigued by the comments re soft vs rigid tubing. I have not experimented with the two versions and logic seems to suggest that rigid would be better as Chris says. However, might it be possible that the air pressure causes the soft tubing to expand and actually create an effectively wider-diameter tube, thus increasing the "surge tank effect"; and, why the soft/clear sounded better?

Like someone recently said, this is mad-scientist territory.

Chris, thanks for the links. A very important topic and one that is not understood by many music consumers. Music is such a personal thing for most of us ("Those eyes!") that it causes most listeners to think of themselves as music lovers vs the more clinical "consumer". In fact, music is a product like any other, and it's creators are entitled to fair compensation for its consumption. I have never understood why many feel a sense of entitlement to essentially steal that product; no different than shoplifting. I remember well when the SNL band had to pull all the charts of Beatles tunes out of our book because it was simply too expensive to perform them. As with most things, what is ultimately paid is negotiable; and, The Beatles, being The Beatles, have no incentive to negotiate anything. It may seem unfortunate, but I say more power to them.

Frogman et al,
There are many reasons why different tubes will affect the sound.
Depending upon the velocity, the air is likely to flow chaotically, forming vortexes and eddies as it moves down the pipe, it is not necessarily laminar.
The geometry of the tube, the roughness of the tube walls, the elasticity of the tube and the purity of the air all affect flow and chaotic behaviour.
Furthermore, air is compressible, which affects flow. And finally as air flows, compresses or decompresses, it can change temperature which affects pressure and therefore flow.
Keeping the tube as straight as possible will reduce turbulence, just like an optical cable with digital - oh the irony.
It is quite complex.

As an aside I would have thought it would be advantageous to have a regulator at the end of the long tube, just prior to the arm, as the length of tube after the regulator will, if my rusty memory on fluid dynamics is working, drop the flow rate going into the bearing.

In other words if 2 of you had the same regulator and 40ft of tube, and one places the regulator at the start of the tube, and the other places the regulator at the end of the tube, then I would expect that you would end up with different flow rates into the bearing. I would at the very least expect a significant impact on the "sound" from where you position the final regulator in relation to the arm bearing.

Suggested music for AB testing - JS Bach Air on the G String : Zoltan Rozsnyai/Philharmonia Hungarica on M&K Realtime for the audiophiles, perhaps Malcolm Sargent/New Symphony Orchestra for the purists on HMV ( 78rpm of course ).

Very interesting, Dover. Thanks for the explanations and music recs.

Regards.

The motivation for putting a soft tube between the two regulators was the finding that a small amount of bleed off between the regulators had a positive effect. This implied that the air pressure was not constant between the regulators. Or for that matter after the last regulator. More pressure equals more flow into the arm since it is not a compensated load and since a needle valve is not a compensated load either it will pass more or less air as the pressure increases or decreases. So the needle valve tends to smooth these pressure changes hence smooth out the air flow.

The soft walled tube acts slightly like a balloon, it tends to absorb small pressure perturbations by expanding with increased pressure. The surprising finding was that this positive effect was present even when the pump had turned off. This points towards the regulators themselves creating tiny pressure changes which the softer tube helped to reduce. Acting in a way like a surge tank.

If this is correct then it may be better to have the regulator remote from the arm. A long length of soft hose to the arm then helping to smooth out the regulator pressure irregularities. Obviously more testing is required. One test would be to fit a surge tank after the regulator in a rig with a regulator close to the arm. Or simply add another long length of soft tube which would be so easy to do....Chris. A small increase in regulator pressure may be required if this was done to compensate for the line losses.

It is fascinating stuff.