Eminent Technology ET-2 Tonearm Owners

Frogman and Slaw.
You planted a seed when talking about the Montronix regulator and controlled air bleed.
I have just teed off a 1/4" needle valve in between the compressor regulator and the second in line regulator.
The tee is configured such that the compressor output is fed straight to the needle valve and the second regulator is connected at right angles. Such that the air going to the arm has to turn 90 degrees.
The needle valve is just cracked open, bleeding only a tiny amount or air to atmosphere. This does not alter the pressure at the arm since there is a significant delta P between the two regulators.

If your regulators are of similar stability as mine you can expect greater solidity and dynamics and just plain better sound.
This test was done when the compressor was off so the air supply was ex the high pressure storage tank only.

Theory is that the regulator must be dithering about its setting. The needle valve, being non compensated clips the peaks of this pressure perturbation.

I found a rare reprint or Myles Astor's TAS review of the Motronix Acuflow Air Regulator:

http://www.whatsbestforum.com/showthread.php?5653-Linear-tracking-Turntables!/page3&highlight=motronix

Apparently, two of the people involved with designing and reviewing this unit are still involved in audio. Miles Astor, PhD is Senior Assistant Editor at Positive-Feedback Online and Marlen Mogilever, PhD, who is mentioned in the TAS article as being "of Motronix" is now the principal designer at Blueberry Hill Audio:

http://blueberryhillaudio.com/index.html

After reading the TAS article, I realize that this unit was more involved than what most of us are now using, i.e. two spring/diaphragm regulators with a surge tank in between. I wonder if we contacted one or both of them that they could/would give us enough detail to be able to reverse-engineer the Motronix unit or, at least, to mod our existing setups to duplicate the Motronix unit's functionality?

Dave

Richard, interesting comments. Eventhough I settled on 18.5 -19 psi (at the arm) based on what my ears tell me sounds best in my system and not simply what my HP manifold was designed for, that pressure is (coincidentally?) about .5 psi above the pressure at which the check valve on my surge tank starts to release some air without fully opening. As the pressure is increased further the released air increases until the spring loaded valve opens fully (at about 20.5 psi or so AT THE SURGE TANK). Makes me wonder if the reason the arm sounds best at that pressure is not only that it is the ideal pressure for my arm, but also that the released air has a similar effect as what the Motronix accomplishes. Thoughts?

Frogman.

I suspect that the check valve you refer to is actually a safety relief valve. And yes it could be the same thing that I am hearing.
It may have an adjustment so you could, entirely at your own risk :-) increase its setting to see if the bleed flow could be stopped but still maintain the same pressure out of the regulator and on to the arm.
Obviously I don't know what your surge tank can take in terms of max pressure, so be careful should you decide to do this.

I read the TAS review and this could be a review of the changes I hear in my system. It is a significant jump in performance and ultra easy to do.
The dimensions given for Motronix unit would imply that any surge tank, if included, would be very small indeed. So maybe it is simply two high quality regulators with a central bleed?

It shows how sensitive the arm is to smooth air delivery. As per my earlier post, the compressor had cycled off, so the air supply was coming only from the reserve in the tank. The "noise" in the air stream could only be coming from the regulators and the associated hosing to the arm.