ENSONIQ DP/4+ User Manual

Section 1 — Controls & Basic Functions
ENSONIQ DP/4+ Reference Manual 9
Ground Loops
Sometimes currents flowing through the ground line generate a signal seen by another part of the
circuit sharing the same ground. In other words, if there are two identical signal paths within a
circuit, they can form a loop which can result in hum and/or noise. If you are using equipment
that has 3-prong “grounded” AC power cords, you may suffer from a ground loop resulting from
the interconnection of this equipment. The following diagram shows how cascading or
“chaining” the output of one 3-prong grounded system into the input of another 3-prong
grounded system with a standard, unbalanced 2 conductor cord (like a 1/4” guitar cable) can
result in a ground loop.
(circuit ground)
+
+
3-Prong
"Grounded"
System
3-Prong
"Grounded"
System
Earth Ground
SIGNAL PATH
Unbalanced Output to Unbalanced Input.
Single conductor shielded cable
Ground Loop
>
<
FIG. 1
(circuit ground)
+
+
3-Prong
"Grounded"
System
2-Prong
"UNGrounded"
System
Earth Ground
SIGNAL PATH
Unbalanced Output to Unbalanced Input.
Single conductor shielded cable
FIG. 2
Fig. 1 shows a system interconnection where a ground loop can exist. Fig. 2 shows a system
interconnection where a ground loop does NOT exist.
The DP/4+ has “ground compensated” outputs, which offer the advantages of balanced outputs
(minimized hum and interference), plus the advantage of a transformer isolated output
(eliminates ground loop problems). The output connector “grounds” are not hooked directly to
the DP/4+ ground, thus eliminating the ground loop. This ground compensating scheme works
on both balanced and unbalanced equipment with standard cables.
Ground loops are possible only on the inputs, and only in the following situations:
1. When a standard balanced cable is used from the preceeding piece of equipment (i.e., a
standard stereo cable).
R
T
R
T
Standard Balanced Cable
Black
Red
Shield
S S
2. When a standard unbalanced cable is used from the preceeding piece of equipment.
TT
Standard Unbalanced Cable
Red
Shield
S S
This does not mean there will always be an input ground loop problem, just the possibility.

ENSONIQ DP/4+ Specifications

General

Brand	ENSONIQ
Model	DP/4+
Category	Recording Equipment
Language	English