User's Manual

4
The minimum electrical service amperage required by a
system of SB-1s is the sum of the maximum continuous
RMS current for each speaker. We recommend allowing
an additional 30% above the minimum amperage to pre-
vent peak voltage drops at the service entry.
Safety Issues
Pay close attention to these important electrical and safety
issues.
Use a power cord adapter to drive the SB-1 from a
standard 3-prong outlet (NEMA 5-15R; 125 V max).
The SB-1 requires a grounded outlet. Always use
a grounding adapter when connecting to un-
grounded outlets.
Do not use a ground-lifting adapter or cut the AC
cable ground pin.
Keep all liquids away from the SB-1 to avoid hazards
from electrical shock.
Do not operate the unit if the power cables are frayed or
broken.
Tie-wrap anchors on the amplifier chassis provide strain
relief for the power and signal cables. Insert the plastic
tie-wraps through the anchors and wrap them around the
cables.
Audio Input
The SB-1 presents a 10 kΩ input impedance to a three-pin
XLR connector wired with the following convention:
Pin 1 — 220 kΩ to chassis and earth ground (ESD
clamped)
Pin 2 — Signal
Pin 3 — Signal
Case — Earth (AC) ground and chassis
Pins 2 and 3 carry the input as a differential signal; their
polarity can be reversed with the input polarity switch on
the user panel. If the switch is in the up position, pin 2 is
hot relative to pin 3, resulting in a positive pressure wave
when a positive signal is applied to pin 2. Use standard
audio cables with XLR connectors for balanced signal
sources.
Shorting an input connector pin to the case can form
a ground loop and cause hum.
A single source can drive multiple SB-1s with a paralleled input
loop, creating an unbuffered hardwired loop connection.
Make certain that the source equipment can drive the total
load impedance presented by the paralleled input circuit. For
example, since the input impedance of a single SB-1 is 10
kΩ , cascading 20 SB-1s produces a balanced input
impedance of 500 Ω . If a 150 Ω source is used, the 500
Ω load results in a 2.28 dB loss.
Differential Inputs