ALESIS PEQ-450 - Manual (Page 39)

chapter 5 • troubleshooting
PEQ-450 Reference Manual 39
TO ELIMINATE HUM IF THE ABOVE HAS FAILED:
A) Disconnect the power from all outboard devices and tape
machines except for the PEQ-450, the mixer and control room
monitor power amp.
B) Plug in each tape machine and outboard effects device one at a
time. If possible, flip the polarity of the plug of each device (turn
it around in the socket) until the quietest position is found.
C) Make sure that all of the audio cables are in good working order.
Cables with a detached ground wire will cause a very loud
hum!!
D) Keep all cables as short as possible, especially in unbalanced
circuits.
If the basic experiments don’t uncover the source of the problem,
consult your dealer or technician trained in proper studio grounding
techniques. In some cases, a "star grounding" scheme must be used,
with the mixer at the center of the star providing the shield ground
on telescoping shields, which do NOT connect to the chassis ground
of other equipment in the system.
Line Conditioners and Protectors
Although the PEQ-450 is designed to tolerate typical voltage
variations, in today’s world the voltage coming from the AC line
may contain spikes or transients. These can cause audible noises,
and they can stress your gear and, over time, possibly cause a failure.
There are three main ways to protect against this, listed in ascending
order of cost and complexity:
• Line spike/surge protectors. Relatively inexpensive, these are
designed to protect against strong surges and spikes, acting
somewhat like fuses in that they need to be replaced if they’ve
been hit by an extremely strong spike.
• Line filters. These generally combine spike/surge protection with
filters that remove some line noise (dimmer hash, transients from
other appliances, etc.). A good example is the Isobar™ series
from Tripp Lite.
• Uninterruptible power supply (UPS). This is the most
sophisticated option. A UPS provides power even if the AC