Eminent Technology ET-2 Tonearm Owners

Frogman.
"gas powered compressor with large storage tank"
This is kinda what I'm using now. It is a small shop air compressor. oil less type. It pumps the tank up to 120psi and switches off. Switching on again at 80 psi. The output is fed thru two regulators in series, bringing the pressure down to 18 psi for the arm.

Doing the Chris T stylus on a stationary record test, results in zero noise change out of the speakers at full volume.

The compressor turns on too frequently at present, about every 7 mins, so I will be adding an auxiliary tank to increase the time span but this is not a priority since... I hear a slight, I think, maybe, possibly, increase in noise while the compressor is running but if it is there at all, it is minute.

Richardkrebs

11-05-13: Richardkrebs
Frogman.
"gas powered compressor with large storage tank"
This is kinda what I'm using now. It is a small shop air compressor. oil less type.

What type of compressor are you using ?

HF Dover.
Compressor is a piston type, which one would think would produce a pulsating air flow. Certainly the piston type loaner they gave me failed the Chris T noise test. The difference this time around is as follows. I'm using two regulators in series. I have a small restrictor between them, ( a trick we sometimes use for low pressure pilot hydraulics). The tank is a little larger. Its set/ reset pressures are much higher 120/80 psi v/s 60/40 psi.
I said earlier that it turned back on too frequently at around every 7 mins. When it does turn on, it only runs for approx 10 seconds. Obviously a larger tank will not only increase the rest time but also increase this on time. I could lower the reset pressure, giving a longer rest time, but there would be a corresponding increase in run time so don't plan to do this since the compressor is acoustically noisy. This can't be heard in the listening room but can in other parts of the house. Also I suspect that the regulators are more stable with a high delta P, contributing to the smooth air flow. This is certainly the case with hydraulic regulators.

Hello fellow ET owners! I recently resurrected my TNT/ET Two (2.0) rig and thanks to this thread and a lot of advice and encouragement from Frogman, the sound quality is now the best I have heard from my system:

Dave's system

After converting the TNT to thread drive and eliminating the tri-pulley system, I made a 2 spring I-beam and moved the weight way out on the I-beam (past 6). All three of these tweaks made a significant improvement in sound quality and it was all free!

I then started working toward improving the air supply to the arm. I was using a WISA 300 and the ET pump together out-of-phase into a makeshift surge tank (could not find the old Airtech in the attic). On Frogman’s recommendation, I build a 4ft long 4” PVC surge tank and bought a Medo AC0910 compressor. Assembled two regulator/filter units, a standard pressure one between the Medo and the surge tank and a second low pressure unit right before the arm. Also built a DIY baffle box to reduce the noise from the Medo. Made it quieter than the WISA. Pics of most of this are at the link above. One other improvement was adding a high-quality check valve under the table just before the arm. I read about this on another thread and it really makes a significant difference in sound quality, similar in magnitude to adding the bigger surge tank.

Called Bruce about a HP manifold for the 2.0 (no more 2.5’s available) and he said it would take about 3 weeks to make one for me, so I am now experimenting with the new air rig and the standard 2.0 manifold. Started at 5psi at the arm. Good improvement over the old WISA/ET pump setup (~3psi at the arm). Went to 7 psi, not much difference from 5psi. Then cranked it up to 12psi. Blacker background, tighter and more tuneful bass, but maybe not quite as open in the highs as at 7psi (only slightly less open, if at all). Perhaps it is just smoother, eliminating some arm resonance occurring at the lower pressure that I mistook for open-ness…

I was wondering if anyone has experience with even higher pressures with the stock 2.0 manifold? I think 12psi is probably pushing it, so thought I would ask here before going higher. From my reading of this thread, it seems that most of you have reached a pressure “threshold” where the sound quality starts to fall off. What exactly do you hear when this happens?

I really like this thread and all suggestions will be appreciated.

Thanks again to Frogman for his excellent tutelage and encouragement.

Dave

I have not used the low pressure bearing with anything other than the stock pump and then the Wisa, which Bruce considers "high-pressure". I know that he feels that the arm with regular bearing performs best with lower pressure, but like you, I experienced considerably better sound with the Wisa's higher pressure with regular bearing. When I later upgraded to the HP bearing it worked well with the Wisa, but nothing like the large jump in performance that I experienced with the move to the Medo compressor (+\- 30 PSI). Welcome to the thread.