How do I choose a tonearm cable?

For my 3rd arm, front left corner mount,

I needed an 8’ length, and the din connector in the arm tube was recessed, so my din connector had to be a ’long neck’ without a shoulder/wider tube. I could not find anything ready made long enough.

I found a long neck shoulder connector, gave the connector info to Pine Tree Audio,

https://sites.google.com/view/pine-tree-audio/custom-shop-work?authuser=0

and they made me a custom cable for not too much money.

meanwhile, while waiting

I bought a cheap $10. Phono cable from Amazon to use while waiting for an expensive Ortofon Phono Cable that my Russian tonearm maker insisted I get to use with it.

https://ortofon.com/products/6nx-tsw-1010

This one is 10’ long, $15.

https://www.amazon.com/Ground-Turntable-Interconnect-UIInosoo-Amplifier/dp/B0978Y1KY9/ref=sr_1_4?sr=8-4

You can use the din/rca adapter shown above, at least temporarily. Then compare any ’better’, custom cable to it, at least you will know if it makes a difference you can hear.

My 3 arm’s cables go to my SUT with 3 selectable inputs, and it’s output cable goes to my preamp.

https://www.audiogon.com/systems/11318

I couldn’t hear any difference. I’ve skipped the SUT, used the various phono cables directly to my preamp’s MM input, switched them, ... I do not hear any difference from my variety of phono cables!

I can have 3 arms/cartridges playing simultaneously, preamp has phono1 and phono 2, identical MM phono inputs, I can compare instantly

I hear differences of cartridges, I hear impedance load changes, and I hear tube change differences, and friend’s various equipment differences, but not cheap/good/best phono cables.

btw, you can always make a separate ground wire, standard green coated wire, nothing special needed, if you want to use any interconnect cable without a ground

Here’s how I approach it. First and foremost, set your budget. Sky is the limit so it’s better to have a guideline to narrow things down. 

Next is to set a strategy: 

1. Best you can find from a reputable company on the used market. 
2. Something recommended from a friend that you’ve heard used in a system you like. 
3. If your TT manufacturer uses a specific cable, consider going with that brand for continuity. Ex: Mofi uses Cardas. VPI often uses Nordost. 
4. Stick with the cables in your system if you already like them. 
 

Once you have a budget set and pick one of those strategies it narrows the field pretty significantly and should give you confidence moving forward. 

If 12 or 10 gauge wire is good for speaker wire, it’s good for any connection. Of course, no matter the wire, there’s no objective difference in the sound. 

I have found out exactly what elliottbnewcombjr has said with cables. I learned the hard way in the past. The end goal to find the lowest possible capacitance cable as a phono cable you can and have your phono preamp make the adjustments to load and capacitance that your cart requires. 

I finally settled on Blue Jeans Cable LC-2 cable for $80. They put on really good interconnects and rejects EMI very good.  

https://www.bluejeanscable.com/store/audio/index.htm

If sound quality is important to you, then you might want to consider Nordost Heimdall, or one of the higher level Nordost cables.  The Hana ML cartridge is good, and you will want a cable that's good enough to make it shine.