- Can I use balanced power on just some equipment and still get good results?
Wherever possible, it is recommended that balanced power be used to cover
the entire production facility including remote equipment that is interconnected
through a/v cables. There are, however, acceptable wiring methods that
have proven to work well when the supply of balanced power is limited in
an area or where remote equipment running on unbalanced AC is patched into
the balanced system. The approach to such situations is similar in every
A good example of this approach is in live sound reinforcement applications
where amplifier load can be extremely large. Power amps usually add very
little noise to a sound system. Most of the noise in a typical P.A. system
is created in the front of house gear, the back line amps and instrument
racks. These are the primary areas to be covered with balanced power --
areas where low level signals are being processed. Mic preamps, guitar
amps, instrument preamps and effects fall under this low-level signal category.
These components must run on balanced AC to demonstrate a significant effect
on noise levels and to eliminate the source of possible problems before
When connecting a system running on balanced power and a system running
on unbalanced power, the signal grounds of the systems need to be isolated.
With balanced audio signals, lift the shields at the inputs. With unbalanced
audio or video signals, use an isolation transformer.
These rules apply for remote hook-ups to permanent facilities, especially
where one of the systems has not yet been set up for balanced power
but the other has. Simply lift the shields at the inputs on the remote
system in similar fashion as is common practice in most splitter snakes
used in remote facilities.
When mixing balanced AC and unbalanced AC, keep in mind that a/v cabling
is the primary path of grounding noise. Lifting audio shields at the inputs
or using isolation transformers where systems are interconnected works
well to eliminate interference anywhere unbalanced power must be used with
balanced power. If fiber optics are used for all signal links, disregard
all of the above and don't worry about it.