Eminent Technology ET-2 Tonearm Owners

Is there a way to tell if I have a high pressure manifold on my ET2? Some sort of marking on the manifold, or a different size? I have a couple of different pumps, but dont want to put on a higher pressure if its going to damage something

05-13-13: Manitunc
Is there a way to tell if I have a high pressure manifold on my ET2? Some sort of marking on the manifold, or a different size? I have a couple of different pumps, but dont want to put on a higher pressure if its going to damage something.

Hi Manitunc

***********************************************
ET 2.0 spindle is about 5/8 inch.

ET 2.5 spindle is about ¾ inch.
************************************************

from my 05/03/2013 post.

One way to tell if its a HP manifold.

So there are many ET2’s out there that have manifolds set up for really high pressures. These were custom ordered. If you want to know if you have a high pressure manifold or not. Push it out – inscribed on it will be XHP or HP. The other method is to hook it up to a compressor and start adding in PSI and see what it can take. If it came with a WISA is was meant for 5-7 psi. The original pump was in the 3 3.5 psi range.

Another way to tell.

Bruce built the manifolds for different pressures based on customer specs. If somebody bought their ET2 or ET 2.5 used and did not know the seller they don’t know what the pressure is – unless it came with the pump.

In order for the air bearing to become rigid it needs to be run at least at the PSI designed by Bruce for that specific manifold. Going over that pressure may produce sonic benefits in a persons room – IMO - this is subjective thing; based on our own room/gear synergies - just like speaker wire and interconnects – hah hah. How do you like that comment ? if a higher pressure works - great.

The original ET2’s were around 3 - 3.5 psi with the Takatsuki SPP-6GA pump.

The WISA pumps were 5-7 psi.

So Manitunc I suggest you try your arm first with the original low pressure pump first if you have it – SPP-6GA.

If it works its the original ET2 manifold. If it needs a higher pressure to work you have a HP manifold.

This applies to both ET 2.0 and ET 2.5’s.

This can be confirmed by contacting BT.

You can’t hurt it with higher PSI – in fact raising the pressure in increments will let you fix any leaks your arm may have if it has been sitting around for 10 years. You will blow off the air hose if anything.

Since we are talking about pumps - I will post how I test my ET2 pumps.

Cheers

Manitunc – just a note on my last post.

If it works its the original ET2 manifold. If it needs a higher pressure to work you have a HP manifold.

If we are talking about an older ET2 arm it may need more pressure because of it being dirty. Its a good idea to clean inside the manifold first. Slide out the spindle and use a toothbrush with alcohol and scrub the inside of the manifold. See page 40 of manual. This is an easy enough procedure and highly recommended for anyone buying a used ET2 with no history.

Cheers

Thekong.
It should be no surprise that the arm weighs in at that figure or even higher with the heavier counterweights. It is neccessary for it to perform well with low compliance carts. This provided that appropriate damping is applied. Lead out wires, air tube, and maybe an oil trough.
An obsessive designer like Andy Payor would have taken this weight factor into consideration.
I agree, it would seem that the Kuzma is indeed a lot heavier, based on its appearance. That said, maybe it uses carbon fibre and other weight saving techniques?

05-13-13: Richardkrebs
Thekong.
It should be no surprise that the arm weighs in at that figure or even higher with the heavier counterweights. It is neccessary for it to perform well with low compliance carts.

This is not correct with respect to the ET2. In my experience adding mass to the ET2 with low compliance cartridges reduces the speed, articulation, transparency and harmonic structure of the music.
Increasing mass with the ET2 also increases tracking distortion and can result in a bass hump of 6-12db by loading up the cartridge with high mass.

A quote direct from Bruce Thigpen

Bruce Thigpen
If the weight is coupled the system resonant frequency would be extremely low, a resonant frequency at 3Hz with a significant rise in response (6-12dB) results, which would affect tracking slightly because of the asymmetric position of the cantilever, we opt for splitting the horizontal resonance frequency into two points and lowering the "Q" which improves tracking.
More important than tracking, the intent was to reduce the modulation effects of low frequency energy (FM and AM) that increase distortion in the cartridge

Quote from ET2 Manual – Bruce Thigpen

P29
It is desirable in most cases ( low to medium compliance cartridges 5x10 dynes/cm – 20x10 dynes/cm ) to use the minimum number of weights, far out on the cantilever stem. This decreases the horizontal inertia of the tonearm while increasing its vertical inertia.

Adding mass to the ET2 increases the inertia to lateral movement and on eccentric records will result in increased cantilever flex and distortion.
Any excessive cantilever deflection in a moving coil will result in phase anomalies as the coils attached to the cantilever are driven into a position where the response becomes non linear. This is what Bruce Thigpen is saying.

Furthermore, with higher mass, once the arm starts moving, the lateral movement is undamped. Cartridge overshoot and uncontrolled cantilever flex are inevitable. This explains why when Richardkrebs added fluid damping the sound appeared to be better controlled or in his words had “greater presence and focus”.
This is because the addition of lead mass and removal of the decoupling mechanism from the I Beam in his ET2 pushes the horizontal mass too high and the cartridge cantilever motion goes out of control. He would be better off reducing the horizontal effective mass by removing the lead he added to his arm and putting back the decoupling in the I Beam that he removed.

If you go to the Eminent Technology website and read the ET1 manual (that’s the arm that precedes the ET2) you will discover that the ET2 was a design decision to move away from the high mass/fixed counterweight model utilized in the design of the ET1 to the low mass decoupled counterweight model utilized in the ET2. These new design considerations embodied in the ET2 resulted in substantive improvements in the quality of sound reproduction.

The decoupled I-beam methodology employed by Bruce Thigpen in the ET2 is designed to minimize horizontal mass and ensure that the resonance of the I-beam and counterweight remains below the horizontal resonance of the arm so that the 2 resonances (arm and beam) do not couple together to produce a large peak resonance in the bass.