[BC] Re: [Pubtech] 3 phase power and audio

[Dale H. Cook]

At 12:07 PM 12/8/2006, Harold Hallikainen wrote:

>I had not heard of the preference for keeping all audio loads on the same
>phase of three phase power before. I'm guessing this is so leakage
>currents to ground are in phase so the chassis voltages on all devices are
>in phase, reducing ground loop currents or common mode voltages on analog
>inputs? Is that the reason for this preference?

Harold -

You are correct, sir. When we started moving additional stations into 
our Lynchburg studios a couple of years ago I found that connecting 
audio equipment in the rooms that I wanted to use with equipment in 
the existing studio rooms resulted in hum. The new rooms were on a 
different phase of the three-phase service. I had an electrician swap 
the phase feed for the new rooms with that for some office spaces so 
that all studios (and my engineering rooms) were on same phase, and 
that eliminated the hum.

Dale H. Cook, Chief Engineer, Centennial Broadcasting, 
Roanoke/Lynchburg, VA - WZZI / WZZU / WLNI / WLEQ
http://members.cox.net/dalehcook/starcity.shtml