Eminent Technology ET-2 Tonearm Owners

Chris.
I have added a multi spring test to the long agenda of things to try.

Liked you cartoon. How true.

Many thanks

Richard - I find the word multi-spring can be misleading.

We are actually joining (glueing) single leaf springs to make one thicker one.

Think of a truck with a leaf spring in the back.
leaf spring suspension

I see this as similar physics except we are working in a horizontal fashion not a vertical one.

The suspension becomes more compliant if we remove leaf springs from that truck. More firm if we add springs. As we add springs we need to add weight to the truck otherwise it becomes bouncy on the road. The ET2 is the same. As we add a leaf spring or two we need to increase VTF if using the same cartridge. We also need to keep the inert lead weights at the end of the I Beam for resonance control – away from the air bearing.

MOST ET2 users go wrong with the lead weights - imo - because they are coming from developed habits with a pivot arm. What do you do to increase VTF with a pivot arm? You bring the weight in more toward the bearing. The ET2 is a unique tonearm unlike any other with a decoupled counterweight. The weight needs to stay at the end away from the air bearing to not impede it and for resonance control – away from the air bearing. So we just add a weight and keep it at the end.

My direct experience – adding a leaf spring (glueing two together) to the ET2 or Et2.5 means it can carry a higher load (heavier less compliance cartridge) better. The result in sound with heavy MC is amazing. Bass is further tuned to your room by turning the counterweight cap downward or upward. This will depend on your actual room and how good your bass compression is with the speakers you are using.

Thanks again to Frogman for bringing the double and triple leaf spring to the discussion here. Bruce has been shipping loose leaf springs out with his tonearms for years. His customers probably look at them and think - wth is this for - maybe a spare ?

Apologies for making this statement without reading all I've missed. (My father passed away and I had been his primary caregiver for several years, this has severely dampened my ability to give my (all) here for quite some time).
Just wanted to add... I've been using aftermarket 80W silicon fluid available at hobby stores with no sonic degredation,( paddle barely skimming the fluid)( I use an oral syringe to add/subtract fluid as needed, it's so much easier than fiddling with the paddle!), also using DuPont NLGI #2 w/ Teflon white lithium grease in my VPI bearing (ceramic ball bearing) to excellent effect.

Ct0517: an excellent description of the goings on with the leaf spring and how it works. I only wish Bruce would have mentioned the effects and the availability of the differing leaf springs years ago. A neccessity at this moment in time and should be included in future owner's manuals.

Hello.

There has been some private questions about the design of my modified ET2.

I have included here some more photos for those who may be interested.
The target design brief was to
- eliminate all unneccesary joints.
- minimise different material count
- eliminate any unneccessary components that could move
- make it as rigid as possible
- make it as inert as possible.

These took precidence over convienence of use.

http://cgim.audiogon.com/i/vs/i/f/1370870032.jpg

The main pillar and manifold are acrylic, since the decission to make the TT plinth out of acrylic was already made. This allowed me to fuse the arm pillar to the TT chassis eliminating one joint. No allowance is made for making the spindle parallel to the platter, after the fact, but I decided to machine the bottom of the pillar should this be required. Measurements showed that this was not needed.
Two cavities are milled into the pillar. In one is glued a lead billet, the other is filled with sand.

4 X M5 capscrews in machined slots pass thru to the manifold. These are loosened and the removable VTA screw is turned to raise or lower the manifold. One turn is approx 1/2 mm (20"). Tightening the cap screws creates a very strong joint. The manifold is indexed to the pillar with a lug each end to keep it level.
The pillar manifold interface is not curved. This because I did not have the machining capability at the time of build.

2 x M2 grub screws pass thru the manifold and contact the bearing sleeve pushing it slightly towards the pillar. At 120 degree increments there are 2 small pieces of shim metal inserted in the gap between sleeve and manifold. Tightening the grub screws presses the sleeve against these shims removing the compliant o'rings from the loop.

Arm lifting is done by hand and the wand rests on a piece of foam at the cartridge end, when off the record.

The goose neck is solid aluminium made from the same grade as the spindle. The oil trough paddle is attached to the goose neck.

This is a 15 year old design, if I did it today there would be a few changes, but the fundamental architecture would be the same.

As you can see my ET has had a little surgery :-)