rackTelescoping Shields

Telescoping shields can be done two ways, some people ground everything at the patchbays and don't connect the shield at the other end. Other people believe the shield should "telescope" from the output, and not are connect at the input. The theory of only connecting to the out put is the rf noise will drain into the output and not be amplified by that input gain. The concept is you are extending the output device's chassis up to an input, but not connecting it at the input so current cannot flow.
If you have severe RF problems this will not work. Sometimes you can put a 0.01uF cap at the between the lifted end and ground, so you still avoid a ground loop at low frequencies (like 50/60Hz), but have even lower impedance bleed-off for HF noise current.
Most of the time I ground everything (small systems and recordingstudios) and only lift one end of the shield if there is ground loop hum. If you have balanced power this is the recommended way to wire the system.On large systems or when multible system are tied together then and carefully planed telescoping methodis needed.
Mic lines must always have the shield connected since the mic does not have any ground, and the shield conductor is needed for phantom power to work. The shield is the negative dc and the twisted pairs carry the positive dc.


A few more tips for wiring right now. One, don't try to pull that nice super soft mic cable through conduit. Use something with a hard jacket like belden 9451 the foil gives you better shielding anyway. Two don't use flex for all the conduit in the studio, use as little as possible, only to break vibration paths. Pulling wire through 10' of flex is worse then pulling through 250' of regular conduit.