Phono cable build question


I’m replacing the phono cables on my Technics 1200 and have decided to use cable that has two conductors and is shielded. My question is what do I do with the shield?

When making regular interconnects with shielded cable, I normally solder the shield to the negative conductor and only on the source side of the cable. Do I do the same with phono cables? I thought maybe I might instead solder the ground wire to the shield, not to negative, and also have a separate traditional ground wire go to the preamp ground terminal.
kommanderkurt

Showing 3 responses by cleeds

kommanderkurt

When making regular interconnects with shielded cable, I normally solder the shield to the negative conductor and only on the source side of the cable. Do I do the same with phono cables?
It isn't clear what you mean here. Typically, you'd connect the shield at the preamp end, and leave the other end - be it to a source or an amplifier - unconnected. That's all part of the "star ground" concept, and how cable manufacturers mark their shielded cables for directionality.
sleepwalker65
Cleeds and Viridian, you are mistaken. The two conductors from each channel connect to the signal carrying twisted pair that is within the cable shield. One cable for right, one cable for left. The shield connects to the black tonearm ground wire at the turntable end and to the phono stage chassis ground at the other end. This gives you a properly shielded connection from cartridge to phono stage.
That you would wire your pickup arm differently doesn’t mean Viridian or I are mistaken. Nor is it clear when you refer to your scheme as yielding "a properly shielded connection" just what you mean. As Viridian notes, your addition of a second ground may actually increase the chance of hum.

The loose, dangling, black ground wire common to many pickup arms is to help reduce ground loops; it can’t shield against RFI because it isn’t constructed as a shield - it’s just a dangling wire.

This is all moot in my system, because I keep the phono cartridge signal fully balanced. It’s wired into a balanced/differential phono stage - there's no need for a shield to reduce RFI.
sleepwalker65
The use of twisted pair cable with a separate shield both provides continuity of shielding for both signal-bearing conductors of each channel, and phono stage chassis ground for the tonearm.
Whatever works for you is fine, of course, but I'd never wire a phono cable as you've suggested, and didn't even when I used a single-ended phono connection.