Avoiding Ground Loops
CIRCUIT.
(3) TO ELIMINATE HUM IF THE ABOVE HAS FAILED:
In today's studio, where it seems every piece of equipment has complex routing and computer logic,
there are many opportunities for ground loop problems to occur. These show up as hums, buzzes or
sometimes radio reception and can occur if a piece of equipment "sees" two or more different paths
to ground. While there are methods to virtually eliminate ground loops and stray radio frequency
interference, most of the professional methods are expensive and involve installing a separate
power source just for t he sound system. Here are some easy helpful hints that a professional studio
installer might use to keep those stray hums and buzzes to a minimum.
Most stray hums and buzzes happen as a result of different parts of the sound system
being plugged into outlets of different AC circuits. If any noise generating devices such as air
conditioners, refrigerators, neon lights, etc., are already plugged into one of these circuits, you
then have a perfect condition for stray buzzes. Since most electronic devices of a sound system
don't require a lot of current (except for power amplifiers), it's usually safe to run a multi-outlet
box or two from a SINGLE wall outlet and plug in all of the components of your system there.
come from audio cabling being too near AC wiring or the power transformers used by equipment
requiring an external supply. If a hum occurs, try moving the audio wiring around to see if the
ceases or diminishes. If it's not possible to separate the audio and AC wiring in some instances,
hum make sure that the audio wires don't run parallel to any AC wire (they should only cross at
right angles, if possible).
(A) Disconnect the power from all outboard devices and tape machines except for 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 pola-
rity 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 gro-
und 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.
Note that the DEP, with its external low-voltage power supply, has no power supply ground. Its
power is transformer isolated for safety, so it has no need for a "safety ground". Signal ground is
connected to chassis ground at the input and output jacks (as it is in most unbalanced equipment).
If the DEP is attached to a metal rack mounting shelf, the assembly shares a common ground
with the other equipment in the same rack. In some cases (such as a star ground scheme), you may
wish to use nonconductive rack rails or rack isolators to avoid ground loops.
(1) KEEP ALL ELECTRONICS OF THE SOUND SYSTEM ON THE SAME AC ELECTRICAL
Many hums
(2) KEEP AUDIO WIRING AS FAR AWAY FROM AC WIRING AS POSSIBLE.
To avoid the possibility of electric shock, never defeat the safety ground found on other equipment
in the system. When in doubt about proper electrical grounding schemes or the power to your
system, consult a qualified, licensed electrician.
.
.
.
.
.
.
.
.
.
.
11
10
10
0
0
10
0
TO AMPLIFIER OR MIXING CONSOLE
LEFT OUTPUT
FROM INSTRUMENT OR EFFCTS SEND
LEFT INPUT
RIGHT OUTPUT
LEFT OUTPUT
TO AMPLIFIER OR MIXING CONSOLE
0
10
0
0
10
10
FROM INSTRUMENT OR EFFCTS SEND
LEFT INPUT
RIGHT OUTPUT
RIGHT INPUT
MONO IN, STEREO OUT.
STEREO.
While still using a mono input, you could connect two 1/4" phone cords
to the [LEFT] and [RIGHT] outputs of the DEP to a stereo amplification system or two mixer
inputs.
Connect two 1/4" phone cords to the [LEFT] and [RIGHT] INPUTS of the DEP from
a stereo source , and two other 1/4" phone cords from the [LEFT] and [ RIGHT] OUTPUTS of the
DEP to a stereo amplification system or two mixer inputs.
.
.
.
TO AMPLIFIER OR MIXING CONSOLE
10
10
0
0
10
0
LEFT OUTPUT
FROM INSTRUMENT OR EFFCTS SEND
LEFT INPUT
6
Содержание PPVERB16
Страница 1: ...DIGITAL EFFECTS MODULE OWNER S MANUAL ...
