- Are there any special problems associated with using balanced power?
Practically none. The only problems noted by technical support involve
clean-up procedures sometimes necessary with some unbalanced equipment
or "dirty chassis" gear. These are relatively rare and can almost always
be fixed. (See Tech Support Bulletins: Audio
Wiring & Grounding and The
"Dirty Chassis" Condition.)
There are a few power sequencers that are incompatable with balanced ac.
In every case, single pole on-off switches on the power sequencer were
used to shut down the audio/video electronics. This results in 60 volts
being fed into equipment power supplies via the unswitched balanced power
line. It may be unusual to think that turned-off equipment can cause problems.
But when a single-pole switch is used to disconnect the power, ground current
leakage that would normally null is dumped on the ground. Furthermore,
if the ground leakage exceeds 5 milliamperes, as a shock protection feature,
the Equi=Tech will shut down. In one case, a studio owner
reported that the GFCI devices on the Equi=Tech would trip
overnight when his studio was shut down. This was determined to have been
caused by single pole switching on a power sequencer. For the sake of functionality,
it is recomended that 2-pole switches be used to disconnect equipment.
At the Equi=Tech system's outputs, the output circuits are
switched twice with 2-pole devices, one is the circuit breaker, the other
is the GFCI device. Either may be used to shut down electronics.
There have also been a few instances where some equipment either demonstrates
little no improvement in performance or causes nuisance GFCI tripping.
In many cases, the manufacturer has used an unbalanced "L" type line filter
which is by design, unbalanced. Sometimes equipment modifications made
in the field will incorporate .01 caps (line to ground) to filter out noise.
This defeats the function of the balanced power system by leaking current
into the ground. Most manufacturers use a "stock" balanced EMI/RFI filter
which is wholly compatible with balanced power. If an "L" type filter is
discovered, it is recommended that it be replaced by a "T" or an "O" filter
or at the very least removed.
(Note: beware of modified equipment and extremely sub-standard
power supplies that can also exhibit the same symptoms for similar reasons.)