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In Reply to: RE: DIY air pressure regulator for an ET-2 tonearm? posted by troporobo on September 21, 2008 at 18:20:08
but you can find low pressure regulators at any business selling gasses, as in welding suppliers and such. You would want a dual stage regulator for the best control of the air flow and need to specify a low pressure regulator as the ET unless extensively modified will not work well for pressures above 35 psi (your fittings will blow off).
Stu
Follow Ups:
. . . such equipment works reliably at very low pressure. The ET is designed for 3 psi. I will have to look. Thanks for the tip
I have a jeweler's acetylene set up: very tiny where with the smallest tip the neutral flame is only one millimeter long, and the pressures are very low 5 psi for the oxygen, IIRC. Welding companies have kits to modify the mechanism and the low pressure seals and diaphragms. Needless to say gas pressure flow is quite tiny.
On my ET the original pump was that square Takatsuki one which is supposed to put out 6 psi at the outlet. A company now defunct was marketing a Wisa modified which could output 22 psi at the outlet. All of these pumps suffer a drop in pressure at the arm manifold because of the aquarium tubing commonly used. Being flexible it causes a pressure drop. In every case a surge tank helps a lot and so does adding a lab grade check valve, a simple polypropylene device allowing air to flow only in one direction. I made my own surge tanks out of old propane tanks, BTW {painted over, they look industrial but not bad.
I have upgraded all the pumps to an Italian Badger air brush model, 1/4 horsepower which can output 140 psi at the holding tank and is dropped down via a built in regulator and filter system. It works well, but as expected is quite noisy and has been exiled to another room and has a power line conditioner of its own to reduce the current surges when the compressor kicks on.
I run the air pressure at about 35 psi although since I used the armored Tygon hose I suspect I am losing a few psi on route. Much more above the 35 psi and the hose blows off the arm manifold. The increase in sound quality is phenomenal, however, with the higher pressure: detail and dynamics increase rather dramatically. The ideal would be to run a high pressure compressor which feeds a surge tank close to the arm where you have a regulator to lower it to the final pressure.
Stu
Another option: I've run a ET 2.5 using a standard craftsman's 10 gallon air compressor (the 10 tank makes a good surge tank) with a lab grade regulator (purchased at a place that supplies air compressor equipment) at the TT. I located the compressor in my garage far away from my listening room and housed it in a well insulated, thick wood compartment to minimize the noise. I, too, run the compressor at around 30 lbs and use the regulator at the TT to turn down the pressure to approx 7 lbs to the arm.
Thanks a lot for your further elaboration. I will use a surge tank also, probably located about 3 meters from the arm itself. I like the idea of a check valve too. I will have to look into the options for different types of hose as you describe
One thing confuses me though - are you saying you are running 35 psi to the mainfold itself? That seems like a very big increase over ET's recommended low pressure
The original ET arm used the Takatsuki aquarium pump. As such, the arm was designed for high volume, low pressure use. Later an after market firm released a modified Wisa extending the pressure to 22 psi from the nominal 6 of the earlier pump. Bruce Thigpen then started producing manifolds with tighter tolerances to enable the use of a higher pressure lower volume pump. With the larger compressors available, you can obtain the high pressures and the volume without requiring tighter bearing tolerances.
Last I spoke to Bruce he could tighten tolerances for a range of pressures: all you need to do is to inform him of the pressures you wish to run ( the arm is back in limited production at $2900). running a standard high pressure manifold I have had no major issues with running high pressures other than popping off the hoses. The barbed fittings and the the fact that aquarium hoses tend to swell under pressure are the chief problems. My local air regulator parts department does not seem to have small enough fitting to convert to a harder hose assembly, although I've been eyeing the medical type respirator fittings: they look very good but again I haven't gone the final step in tracing the fitting parts.
I used zip ties and RTV to lock down my hose ends and it seems to hold up to 35 psi with no issues (cheap and easy). I used a 1/4 thick wall reinforced Tygon hose for the air line from the compressor to the the surge tank. Had I owned a home, I would have installed metallic pipe. It would have been smaller and more hidden and probably kept the line pressures higher.
There is one danger, however, as the floating arm approaches the manifold, the air blowing past the seal sometimes will catch the arm wand structure and blow back the arm at the end groove of the LP. It is definitely an issue at the pressures I like to run the arm and I actually moved my arm over a small amount by a 1/4 inch or so to compensate. I haven't measured the pressure at the manifold but I suspect it is around 30 psi.
I got my check valve at a chemical supply house and it has tapered ends. I found it necessary to clip a little off the ends in order to increase the amount of air flow through the check valve for proper arm operation. Using the check valve was as effective as adding the surge tank in my experience.
Good luck. With the higher pressures, the ET can compete with most of the super arms in the mechanical department. I do notice that ET has a carbon fiber tonearm available: that ought to be interesting. I rewired mine with Cardas 33 gauge for a nice improvement and using the AMS silver wire was also very nice. In order to minimize the junctions I simply ran the wire down the arm wand and out to a junction box behind the moving arm area with very good results.
Have fun!
Stu
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