The Korf Blog

The inside story: our research, development and opinions

20 May 2019
Headshell Performance — Jelco HS-25
In this series of articles, we measure the performance of removeable tonearm headshells. Today, the subject is a Jelco HS-25, a premium headshell in the Jelco lineup.

The headshell is made of magnesium alloy and weighs 12.5 gram without wires or mounting hardware. The fingerlift is attached by two tiny screws.

Jelco's bayonet mount is slightly different from the typical one. While usually the location pin is only protruding at the top, Jelco's is also sticking out at the bottom. This definitely improves the mechanical connection, but makes the headshell incompatible with some tonearms that only have the top slot.
The surface is anodized black, which doesn't really help when attaching an accelerometer.


The Jelco looks exactly the same as Sumiko HS-12, sans the finger lift, so it should perform more or less the same... but it doesn't. The oscilloscope trace of Jelco's IET measurement is nothing like Sumiko's.
Jelco HS-25
Sumiko HS-12
The Jelco rings a lot "cleaner". Here is the spectrogram comparison between Sumiko HS-12 and the Jelco HS-25:
Frankly, I expected them to be alike. After all, a Sumiko is just an OEM version of a Jelco, and they shouldn't be different at all.

But the reality has a funny way of shattering the assumptions. While the similarities are clear (same main mode at about 750-800 Hz), the differences are abundant.

Jelco has an additional and quite pronounced mode at 550 Hz, but no 2.5 kHz peak that is so dominant with the Sumiko.

This surprised me so much that I suspected some irregularities in measurement signal chain. A few days later, I've re-done the measurements with a different DAQ. Here's the result:
No difference. The signal chain is ok. It's the Jelco that is quite different from Sumiko.
The waterfall plot has no surprises:

For IET measurement with a Technics EPC-U24 cartridge, we're comparing the Jelco to the Sumiko again.
Chalk and cheese. But these 2 kHz and 3 kHz modes are common.

I think I must redo the measurements of the Sumiko headshell with the cartridge attached. The lack of the main mode around 700 Hz points to some kind of error.
OEM version of same headshell is significantly different
The original Jelco HS-25 turned out to be quite different from its OEM version, the Sumiko HS-12. The examples I have are separated by a couple of decades: Sumiko was made in the 1990s, and the Jelco is recent. Perhaps Jelco switched to a different alloy composition?

Today's findings are one more reason to stop "listening with one's eyes". Very similar, even visually identical, devices can have different measured performance. I wouldn't be surprised if they sound quite different too.
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