4
DRAWMER
T
HREE
-
SUM
O
PERATOR’S
M
ANUAL
The THREE-SUM is designed for standard 19" rack
mounting and occupies 1U of rack space. Avoid mounting
the unit directly above power amplifiers or power supplies
that radiate significant amounts of heat. Always connect
the mains earth to the unit. Fibre or plastic washers may
be used to prevent the front panel becoming marked by
the mounting bolts.
INSTALLATION
AUDIO CONNECTIONS
The inputs and outputs are electronically balanced on conventionally wired XLRs (pin 1 screen, pin 2 hot, pin 3 cold and
XLR shell is connected to chassis). The operating level is nom4dBu. Balanced use is recommended.
• Interference:
If the unit is to be used where it maybe exposed to
high levels of disturbance such as found close to a TV
or radio transmitter, we advise that the unit is oper-
ated in a balanced configuration. The screens of the
signal cables should be connected to the chassis con-
nection on the XLR connector as opposed to connect-
ing to pin1. The Three-Sum conforms to the EMC
standards.
• Ground Loops:
If ground loop problems are encountered, never dis-
connect the mains earth, but instead, try disconnect-
ing the signal screen on one end of each of the cables
connecting the outputs of the Three-Sum to the
patchbay. If such measures are necessary, balanced
operation is recommended.
fig.1
TYPICAL THREE-SUM SETUP
