Eminent Technology ET-2 Tonearm Owners

Rebounding arm fix!

I thank the forum contributors for their suggestions.
Careful leveling has mitigated but not solved the problem. Rebound is now observed only with some records, perhaps those with runout grooves more steeply pitched.

I assume that energy is stored in the I beam spring upon inward acceleration of the arm as it encounters the more steeply pitched runout groove, then suddenly decelerates when the groove becomes circular nearest the record center, and the Ibeam with associated mass gives up its energy, pitching the arm back toward the periphery.

Bruce Thigpen offered to send me an I beam with a less compliant spring, which may solve the residual problem.

Arm setup was impaired by my inability to find my stylus pressure gauge. It is useful to know that a US dime weighs ~2.2 grams. That made it possible to jury rig a balance so that my Benz Micro Ref could be set to that pressure.

Hi Philcoffino – welcome to the thread. Interesting point about the smaller circle and built up energy ? I need to give that some thought. The smaller circle is what caused the most problems for me when I tried to convert a belt drive designed TT to thread drive. Pitch stability suffered when longer thread was used.

I will say “again” any one with an ET-2 on a suspended TT needs to pay extra attention to detail. Here are 3 additional leveling tips based on taking down and remounting the ET 2.0 / 2.5 over 20 times in the last year. 4 different tables plinths / no plinths and also 4 armpods.

These 3 techniques saved me a lot time and frustration.

I went to one of those neat hardware stores and bought a level that is as close to the same length/size as the ET2 Straightline Jig.

1) Place it on the platter in the EXACT line that your ET-2 straight line alignment jig would go – levelling this way ENSURES your platter is level in the path the arm will take.

2) The tonearm air bearing spindle is not IMO in the same exact level plane as the tonearm armpost it attaches to. It a physical connection with bolts – DON’T TRUST IT. Some of these arms are old now. Many people level the arm post. IMO - this is a mistake.

Use Blue Tac (Fun Tac) a little heavier than the cartridge on the counterweights to raise the Arm Tube and Cartridge and have the Bearing Spindle float with gravity. Adjust armpost vertical screws until it does not move either way.

3) While arm is floating (in 2) move wires around with pencil or your finger – Fix/dress the wires so they don’t affect the arm. Do this with the arm raised at the START and END of the record.

If the above three points are done the stylus "run-in" and "run-out" should be the same.

Thoughts?

Philcoffino: Your observation in regards to the runout groove being more steeply pitched is right on. Every record is different. I was curious as to what kind of damping if any, you are using? Trough, magnet, or none?

By the way, I've been reading with great interest regarding the leaf spring/s and their effect. I realized I had two and decided to take a look at the one I had been using for years. When I removed it, I noticed that the leaf spring had become unattatched. I replaced it with my other I-beam and what was instantly noticable was less movement which has translated into better sound. I plan on investigating this further.
I've made some other changes to my TT isolation and as soon as it is possible, I'll update my virtual system if anyone has any interest in following this. I have a custom armboard project in the works also.

Slaw-

I am using no damping. Have seen descriptions of magnetic damping, but not sure where to place a magnet or what sort to use. Meanwhile I am awaiting arrival of a "double spring" I beam, presumably one that is stiffer than my present one.