Which EPA-100 bearings?

I picked up a nice EPA-100 a few months ago in excellent cosmetic and functional condition. The bearings seem good, as far as I can tell—it passes the WallySkater stiction test with aplomb, anyway. And it sounds remarkably alive and resolving with no obvious behavioral issues.

Still, given the famous fragility of its ruby bearings and the age of its internal wiring, I suspect it can sound even better with some refurbishment—new bearings, new wiring, whatever it needs. I think this tonearm is good enough to warranty the investment. 

JP at Fidelis Analog has graciously agreed to work on it. He offers, and prefers, silicon nitride ceramic bearings (Si3N4) for both performance and longevity. He also has a supply of ruby bearings for those who prefer to keep it original. So, I have a decision to make. I like the idea of keeping it stock but I want the best performance and, most important, sound.

Has anyone compared the sound of Si3N4 bearings to the original ruby? Has anyone replaced the ruby with Si3N4 and regretted it?  I’d like to hear some hands-on, ears-on experience before I make the choice.



Dear @wrm57  : I owned the 100 and the 100MK2 functioning in perfect condition.

If you want to internal re-wiring go a head, recomended.

Now, for the ruby bearing please do it your self next question:

ceramic bearings always exist even when the EPA 100 was designed: do you think that been designed by Technics that if ruby were not the best quality performance bearting tonearm design they made a mistake when choosed ruby?, Technics is second to none even today and they does not makes that kind of design mistakes. In those times the japanese competence was really hard on  tonearms.


Btw, I owned  the Mission top of the line that came with ceramic bearings and was not good enough till I changed by stellness ones.


Regards and enjoy the MUSIC NOT DISTORTIONS,


'Has anyone compared the sound of Si3N4 bearings to the original ruby?"

Drag coefficient has  a sound?

Ruby's and Sapphire are fragile and may be difficult to ensure the parts produced from it in a Tonearm or TT, will be intact at the end of a Long Freight Journey.

 Si3N4 is commonly seen used as a bearing in place of a Steel Ball, the Si3N4 is known for its robustness, and is seen at interfaces where impact damage is a risk.



@pindac , thank you for those links. Very interesting, especially moisin’s comments.

@rauliruegas , I appreciate your experience in this matter, as in others analog. Is it that you think the ruby material (actually sapphire, as it turns out) has a preferable sound to the Si3N4? I ask because the hardness and density of the two materials seem virtually the same, which means their friction and stiction will be pretty close to each other when the bearings are unflawed, which means their mechanical performance should be pretty much the same. So what’s left? Whence your strong preference for ruby?



my understanding is the silicon nitride bearings produced today have a far truer surface ( in terms of roundness ).

In terms of sound - Isamu Ikeda ( Fidelity Research, Ikeda ) always eschewed the use of jewelled bearings, describing the sound as brittle, but bear in mind his cartridges are low compliance and demand very good bearings.

Having said that I would not recommend very low compliance cartridges be used in the EPA100. The top Technics cartridges of the day were medium to high compliance.

In my view its a no brainer - if it were my arm I'd install silicon nitride bearings.

JCarr has replaced the bearings in his own EPA100 with silicon nitride.






Dear @wrm57  : Ikeda opinion it's  only that an opinion and that's all.  There is no brittle and it's not true that the EPA 100 is not for low compliance. Again , Technics makes that kind of mistakes.

The EPA 100 comliance cartridge range it its counterweigth wise mechanism says in the tonearm manual from 5cu and I had first hand experiences with the EPA 100 and several low com'liance japanese cartridges with outr any single trouble.

In the other side, my advise is that you go step by step with your tonearm and for me first step is th internal re-wiring that you could do it with Audio Note UK silver wire that's excellent.

Then listen it for a while and decide if in true the tonearm needs a bearing change: don't change what is in good operation, remember?