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To measure a cartridge or not?

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MS61 View Drop Down
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    Posted: 18 May 2022 at 8:27am
I´m contemplating about measuring capacitance of phono interconnects/arm wires and my cartridges (only MM ones). Plus inductance of carts. But is it safe (for layman) or not?

Thinking about Peak Atlas LCR45 or DE-5000 LCR Meter. Or some cheaper one?

Just preparing for long winter nights and appropriate time for my hobby. My goal - to fine-tune capacitance of MM carts (mostly AT ones) and Accesion MM. No more random experiments (this and that cable or DIP switch on/off).

Michal
Technics SP15 / Audiomods 6 / SH-15B3 plinth / Audio Technica AT 150 Sa / Accession M / Genelec 8030 + RME ADI-2 Pro ADDA
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 18 May 2022 at 9:22am
We use LCR40's but after reading the LCR45 page, I think I may upgrade, simply because it measures below 1uH.

However, the LCR40 will do all you require and might be less confusing to use.

Since we started using LCR40 component testers a few years ago, I think I've measured every cartridge I have, and they still work. Just make sure to disconnect one side (pull the cartridge connector off) if measuring in situ on the arm.

The probes are meant for component wires, so will not clip to phono plugs and so you'll need to obtain a phono socket having PCB pins. This will add its own capacitance so measure the socket's capacitance and subtract it from your measurements.

It will not measure an input to a preamp because it cannot work out what it's supposed to be doing. If the preamp is on, without an input connected, more than likely it will behave in a strange way. If it is off, then it still won't know what it's intended to do.

However, with a little bit of ingenuity in disconnecting things, you will be able to measure the capacitances of arm cables, and if you can unplug the arm interconnect, you can measure the capacitance of the pairs of wires in the arm tube.

When you measure those, you will be aware that there is also capacitance between left and right arm tube wires, and so that will contribute to crosstalk at mid to high frequencies. At that point, maybe your mind will become aware of this great design fault which nobody has yet addressed. Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote patientot Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2022 at 12:25am
If you want to go really all in for your AT carts, I would try to get a JVC TRS 1007 test LP. Unfortunately they are no longer made and a bit hard to find these days. The reason I recommend it is because that the test LP that many manufacturers use in their on-site testing facilities, including AT. I wish I had one.

With the Accession you can record the sweeps off the test LP using the "flat" function (I believe these are no-RIAA records, like other sweep test LPs I have), then graph the results and see what your FR looks like. You can compare the results at different capacitance settings and see what looks/sounds best to you.

Measuring the resistance and inductance of the cartridge is a good starting point, because the values can vary a bit from factory spec. Running calculations with those specs does have some limitations since it doesn't account for cantilever resonances. Still, it will give you a rough idea of where you need to be.

FWIW the AT I'm running at present is loaded at ~180pf + 36K. I found that was the best compromise with the equipment I have. YMMV.
Reflex M + PSU-1 used with AT150-40ML, AT VM95ML, Stanton 680mkII + Ogura, and Shure M35X cartridges.
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