My unipivot tonearm

[Eggzy]

I wonder whether this is worth a go...

[nghiep]

The V shaped counterweight mounting increased the arm effective mass considerably. If one moved the V shaped counterweight mounting aft of the pivot, one would decrease the effective mass and use the counterweight as an lateral balancer also. One can also tune the unipivot arm by the arm effectivemass because the amount of friction and the pivot interfacing materials at the pivot affect the sound. One can also counterweight the arm by a ballon with a lighter am effective mass also. Counterweight located aft of pivotal point is a good thing in tonearm.

[EC8010]

A friend of mine had a similar idea and floated a ball in goo as a before-pivot counterweight. I told him at the time it would have even more effective mass than the SME weight he was replacing... (Quite apart from what it did to the restoring force of the knife-edges.)

[baggins]

Just been reading this thread -- Nice arm

It occured to me to ask my usual silly noob question :-

If one could theoretically hang a cartridge from a proverbial sky hook would the mass of the cartridge body alone be sufficient to enable the stylus to track large excursions? and if not how does one calculate the minimum rotational inertia an arm should have?

[wmincy]

nghiep, thanks for your suggestion. You and my father had the same idea, and soon i'll bring on with a new one.

In these days we put the tonearm in testing, to assist its performance.
We tried with 3 cartridges, all are low compliance type: Sumiko Bluepoint, Micro Benz Silver and Grado Sonata Wood. The first two, high output, sounded with deep powerful bass and many details (playing with Wham! 45 rpm), Micro Benz prevailed in bass responce, Sumiko Bluepoint was more in sustain. Both are high quality cartridge! Superb sound! In term of cost/performance.

Today we tried the Grado. New in the box, haven't run in. It sounded slower, warmer, more "analog" and digged more information. Hearing Carol Kidds, her voice was sweet and involved the entire atmosphere. Pavarroti's voice never fatigued.

[rfj5106]

Wonderful arm. Can you post some more dimensions on the V shaped component?

[nghiep]

Hi, wmincy
I think all three cartridges have medium compliances. I also think your design providing more stabilization than aft pivot counterweight. Your counterweight controls lateral movements between the cartridge and pivot rather than aft of pivot point. The normal formula for tonearm effective mass may not work on your design. Your tonearm effective mass may be lighter than appeared. Your unique design threw conventional wisdom out of the window. That's one creative idea.

[Mikewong]

Attached with the turntable(a modified Gyro back in 1992 where the sub-chassis was my design back in 1982 in one of my diy turntable) with the unipivot+bluepoint(in function) and the SyrinxPU3+Benz micro silver(as a reference).Stability is the key factor of this arm,and I love it This combination does not shy before the Syrinx PU 3.Anyway there are areas need to be reconsidered and rethought for further perfection.And his second and third (my modified version---Wmincy's father) versions will be coming up soon.

[fergs1]

Greetings, have there been anymore developments with this design. Its a real corker.Well done
peace and goodwill fergs