dbx 166xs User Manual page 17

dbx 166xs
Section 3
Making Connections
Input Cable Configurations
The 166xs has an actual input impedance of >40k in balanced or unbalanced configurations.
This makes the 166xs audio input suitable for use with virtually any source impedance, low
or high. The 166xs input jacks are wired in parallel. The phone jack TIP (+) connection is
internally wired to the XLR pin 2, the RING (-) is wired to pin 3, and the SLEEVE (shield)
is wired to pin 1. Note that pins 2 and 3 are the reverse of certain older dbx and other
manufacturer's equipment, but if the same connection is used at both the input and the
output, the signal will be correctly polarized ("in phase").
Reversing the input wires to the input terminals will result in the output signal polarity being
the opposite of the input signal ("180° out of phase").
Output Cable Configurations
The 166xs outputs are wired in parallel: either the XLR-type OUTPUT jack or the 1/4"
stereo phone jack are capable of driving a 600Ω load. The phone jack TIP (+) connection
is internally wired to the XLR pin 2, the RING (-) is wired to pin 3, and the SLEEVE (shield)
is wired to pin 1. Note that pins 2 and 3 are the reverse of certain older dbx and other
manufacturer's equipment, but if the same connection is used at both the input and the
output, the signal will be correctly polarized ("in phase").
166xs
SIGNAL FLOW
Figure 3: Signal Flow (Balanced Connection)
Grounding
For maximum hum rejection with a balanced source, avoid common grounding at the
166xs input and output. Most balanced (3-conductor) cables have the shield connected
at both ends. This can result in ground loops which cause hum. If hum is a problem, try
disconnecting the shield on one or more of your cables, preferably at the input of a device,
not at the output: Ground the shield of the input cable at the source device (leaving it
unconnected at the 166xs INPUT) and ground the shield of the output cable to the ground
terminal of the 166xs (leaving it unconnected at the receiving device).
The shield is pin 1 on the XLR, SLEEVE on a 1/4" TRS.
13