Signal Connections; O O; Q Q; Q A - Electro-Voice 7300A Owner's Operation And Service Instructions

Operating and Service Instructions for the Electro-Voice 7300A Power Amplifier
not let the thermometer touch the
metal chassis because the chassis
will be hotter than the ambient
air. If the air temperature exceeds
60 °C (140 °F), the equipment
should be spaced at least 1.75
inches apart or a blower installed
to provide sufficient air movement
within the cabinet.
WARNING: Do not operate the
amplifier within a completely
closed unventilated housing.
3 SIGNAL CONNECT¬
IONS
3.1 Input Connections
Balanced input connect¬
ions may be made to either the Vi"
phone (TRS) or the female XLR
connectors. For single-ended in¬
puts, strap the low (—) input to
ground (pin 3 on XLR or Ring on
Va" phone). Otherwise, the elect¬
ronically-balanced input stage will
see 6 dB less input signal level
than with a balanced input. Refer
to Figure 3 for typical input con¬
nections.
3.2 Line Output Connect¬
ions
The XLR and Vi" phone
connectors are wired in parallel.
Pin 2 of the XLR is the Tip of the
Vi" phone connector, and pin 3 is
the Ring. Since the input imped¬
ance of the electronically-balanced
input stage is high (15 kohms),
there is minimal loading on the
signal source. When the input
connections are made to one con¬
nector, the other may be used as
an auxiliary line output to feed
other high input impedance equip¬
ment. Refer to Figure 3 for possi¬
ble applications.
3.3 Output Connections
Output connections eire
made to the binding post connect¬
ors located on the rear. The Red
post is the high
(-I-)
output and
the Black post is the low (—) out¬
put. Refer to Figure 4 for typical
output connections.
3.4 Output Cable Selection
Speaker wire size plays an
important part in quality sound
systems. Small wire gauges can
waste power and reduce the damp¬
ing factor at the speaker termi¬
nals. This can add coloration and
muddiness to the sound. To help
offset this problem. Table I has
been assembled to enable you to
calculate the power losses in the
speaker cable.
3.4.1 Calculating Power
Losses with 8 ohm
Loads
To calculate the total
power loss in the speaker cable,
multiply the power loss per foot
(or meter) of the 2-wire cable
selected from Table I by the len¬
gth of the cable in feet (or met¬
ers). For example, suppose an in¬
staller uses 160 feet of 10 GA 2-
wire cable with an 8 O speaker
system. The total power loss in
the cable is:
Total Power Loss in cable
= 0.0509
watts/foot X
160
feet
= 8.1 watts
Does this mean that whenever the
amplifier produces 200 watts of
output power, 191.9 watts (200
watts minus 8.1 watts) will he
delivered to the 8 ohm load"? NO!
The actual load impedance is 8
ohms plus the resistance of the
cable (0.00204 ohms/foot times
160 feet) for a total load impe¬
dance of 8.3264 ohms. At the 8 G
rated output power, the output
voltage is 40 V rms. Therefore,
the amplifier produces 192.2 watts
with this load instead of 200
watts. This was calculated by
2 Electro-Voice
®
a Mark IV Company