The Korf Blog

The inside story: our research, development and opinions

12 May 2020
On the Importance of Bearings
There's a well-known children's ditty where animals try to find out who took the cookie from the cookie jar. Accusations and denials are exchanged, each round ending with "Not me! Then who?"

This ditty was stuck in my head as I was trying to understand the low-frequency behaviour of tonearms and cartridges. The difference in tracking ability is obvious and huge. But if the low-frequency resonance is not the culprit, then who?

I might have an idea.

We've taken two tonearms that have an effective mass within a gram of each other. One is a Jelco that we have used for many tests. It is equipped with fairly good precision bearings that have a typical starting torque of about 80 microNewton/meter.
The other is our prototype using flexure pivot bearings. They have zero starting torque. Zilch, nada, none whatsoever.
I've put the same cartridge on both—a Sumiko Pearl. The downforce is exactly the same, and so is the antiskating.

I've given both the most warped LP that I own: a copy of Billy Joel's "Storm Front". The first song on side 1 is the most affected. In fact, the cartridge bottoms out at the beginning of the track, so I had to start from the middle.

Here it is:
Sorry for the audio quality, it came straight from the camera mic and not directly from the preamp. Still, I think the difference is quite obvious.

So Who Took the Cookie?
There are a lot of elusive vinyl playback ills that are difficult to remedy: sibilance, inner groove distortion, mistracking on warps. Hapless enthusiasts endlessly readjust the cartridge position, swap needles, glue pennies on headshells and so on and so forth. But, in >90% of cases, the inadequate bearings are the real reason for these problems.

Tonearm makers don't like to talk about bearings. Really good rolling bearings are seldom used: they are both expensive and fragile. Plus, they aren't really a very good selling point. The tonearm with poor bearings looks exactly the same as the one with great bearings. Only the latter would require an installation by a competent technician, and it's bill of material cost would be at least $100 higher.
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