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The Korf Blog

The inside story: our research,
development and opinions

4 March 2021
Production Tonearm — Second Prototype
We have already shared a little bit of information about our tonearm project. It's coming along quite well, and the arm is getting closer to the production shape. Getting it right is surprisingly hard — but I believe it's worth the extra effort.

The Arm
We have completely redesigned the central part. It is a lot more rigid now, and I think it looks better too.

The antiskating is still magnetic — would be a pity to ruin the perfect starting torque performance of a flexure bearing with some sort of a draggy mechanical arrangement.
The counterweight is inherited from the V1 prototype for the time being. As we already know, the things hanging off the back of the tonearm matter a lot. The adventure we went through with the counterweight configuration is worthy of a separate post, but this would have to wait until V3. The next prototype will have a very different counterbalance arrangement.

Another subject worthy of a separate post is the influence of the vertical bearings on the sound. V1 used zirconia ceramic. The two V2 prototypes use silicon nitride and normal steel bearings. Sonically, they might as well be two completely different arms.

The Measurements
The previous prototype version measured quite well with the exception of a strong 690 Hz mode. It's one of the arm tube fundamentals, and hard to get rid of completely. Most say it's quite benign... but is it?

Damping it would be contrary to our philosophy (and would not help much). So we had to invent a different approach that would have to remain secret for the time being. Here's what it looks like in the measurements:
We have almost halved the 690 Hz resonance. The improvement is quite easily to hear. I think this is the final armtube configuration that would go into the production version.
PS the low frequency hump is 50 Hz noise in the signal acquisition chain. The much lower 5.5 kHz mode is the result of incorrect cable dressing.

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