are the
‘banana’ plug connectors
with 3/4” spacing. Bare
wire can be inserted through the vertical holes in the shafts,
which are visible when the caps are unscrewed. To be
certain that no strands of wire are unsecured, it is best to tin
the wire end before insertion. Alternatively, a spade lug
soldered to the wire end will make a good connection.
Make all connections between loudspeakers and the ampli-
fier with the power shut off to avoid loudspeaker damage.
Select wire of sufficient size to preserve the high damping
factor of the PRO5000. The minimum recommended wire
size is
#1 6 gauge
when high power output is expected.
Larger wire sizes are necessary for long runs, or if the
speaker impedance is less than 8 ohm.
PHASING:
Consistent phase relationships are important when con-
necting speakers in order to enable full bass reproduction as
well as midrange and high frequency time alignment. To be
sure all speakers in a system are wired in phase to the
amplifier, each ground or - speaker terminal should be
connected to its black ground terminal on the PRO5000,
and the sp terminal to the corresponding red
terminal. Speaker connecting cable identifies one wire
from the other by color of the wire, or by marking or
coloring the insulation. NOTE: In the special case of
monophonic operation of the PRO5000, (described below)
different speaker connections are employed.
GROUNDING
The black output terminals of the PROS000 are connected
together internally and grounded to the chassis. This fa-
cilitates the use of external devices which use a common
ground connection, such as some headphone junction boxes.
You must be sure that the ground or shield connection from
such a device goes to a black terminal on the PRO5000.
NOTE: No such connection may be made when the
PROS000 is connected for bridged mono operation.
The back panel of the PRO5000 also contains a chassis/
float groundswitch forground isolation. This switch should
be set for minimum system hum and/or noise.
BRIDGED MONO OPERATION:
To drive a single loudspeaker with increased power capa-
bility, the PRO5000 can be operated in the bridged mode
which drives both channels with the same signal and
combines their output to deliver more than 900 watts to an
8 ohm speaker. In this arrangement, the speaker is con-
nected only to the two red output terminals. The channel A
terminal is the "+", and the channel B terminal is the "-"
connection. No connections should be made to either black
output terminal in this configuration.
OPERATION
APPLYING POWER:
Standard practice is to turn power amplifiers on last and off
first in the chain of electronics. This minimizes the likeli-
hood of damage to the load from turn-on and turn-off
transients generated by source equipment. The PROS000
provides built-in protection from such transients by incor-
porating a delay of approximately 3 seconds before the
relay connects the loudspeakers. If a longer delay is re-
quired, contact the Hafler Technical Service Department.
The pilot lamp in the power switch will glow whenever
power is applied to the PRO5OOO. If it does not light, check
for a blown internal AC line fuse. Otherwise, check the line
circuit breaker for a fault.
FRONT PANEL INDICATORS:
The presence of any signal above the noise floor will
activate the green ‘Signal’ lights for each channel. The red
‘Clip’ indicators are activated by a comparator circuit which
triggers when the output distortion level reaches approxi-
mately 3%. They indicate when the demands of the ampli-
fier exceed its output capability. Because the dynamics of
good source material may include steep waveforms which
reach these limits for a small fraction of a second, normal
actuation would cause them to flicker so briefly that the eye
would miss it. In the interest of giving maximum informa-
tion, a “hold” circuit is included which extends these brief
pulses to about 1/4 of a second, so they will be clearly
visible. However, these occasional flashes do not indicate
that the amplifier is being substantially overdriven. Thus,
these lamps may operate quite differently from similarly
marked indicators on other amplifiers.
GAIN CONTROLS:
The gain controls for each channel are precision potenti-
ometers, designed for very low distortion. Unless there is a
specific purpose for an intermediate setting (such as level
matching), the gain controls are usually fully advanced
clockwise. This is the setting for which the amplifier’s
sensitivity and voltage gain are specified. Note that in the
bridged mono mode, the channel A control determines the
gain of the amplifier.
DC OFFSET:
If at any time the DC voltage rises to an unsafe level at the
outputs. the relay will disconnect the loudspeakers from the
amplifier. It should be noted that very high levels of low
frequency energy can sometimes imitate DC at the output,
and might activate the relay protection inappropriately. If
this becomes a problem, the level of DC protection provided
can be changed by consulting the factory.
