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Operating Manual - Powerflex Multi-Channel 70V Power Amplifier
Po w e r f l e x
670 shown -
Po w e r f l e x
470 only has
inputs 1-4.
channel 1, a single input channel connection can supply
all amplifier channels with the same signal before their
level controls. This is useful in multi-zone applications
where each zone level can be controlled separately and
only one input connection is needed.
7.4
80Hz Low Cut Filter
Each input channel has an internally se-
lectable 12dB/octave 80Hz high pass filter. This filter is
useful when driving low quality 70V step-down transform-
ers which typically saturate (high distortion and low im-
pedance) at low frequencies. The amplifier is factory
configured with this filter bypassed.
To enable the 80Hz high pass filter for a given
channel, a qualified service technician can remove the in-
put panel and reposition one of six jumpers labeled "HPF"
on the top circuit board assembly, each near their respec-
tive channel's level control. When the filter is engaged,
the respective channel's frequency response will be -3dB
at 80Hz, -12dB at 40Hz, and -24dB at 20Hz.
7.5
Input Level Controls
The Input Level controls attenuate the
input signals from 0dB to -infinity (OFF). For best head-
room performance, it is recommended that the Input Level
controls always be operated at full level (0dB attenuation).
Each channel's level is controlled by it's respective Input
Level control regardless of being in Independent or Paral-
lel mode. However, when a Normal/Bridge switch is de-
pressed, the odd numbered channel's level control will
control both the even and odd numbered channels.
8
7.6
Normal/Bridge Switch
The Normal/Bridge switch is used to operate two
adjacent channels (1 and 2, 3 and 4, 5 and 6 on the PF670)
in bridge mode to drive 140V lines. Pressing a Normal/
Bridge switch in (Bridge mode) disables the even-num-
bered channel's input connector and level control and in-
ternally routes the odd numbered channel's input signal to
the next higher even-numbered channel with the phase in-
verted 180 degrees. The odd-numbered channel level then
controls both channel levels equally. The output of two
bridged channels is then taken from the two (+) output
screw terminals of the respective channels to provide twice
the power at 140 volts.
7.7
AC Inlet
Powerflex amplifiers can be configured by the cus-
tomer for operation at either 115VAC or 230VAC mains.
Switching from one to the other simply requires the fol-
lowing steps:
1.) Unplug the amplifier from the wall and re-
move the power cord from the rear of the amplifier.
2.) Using a small screwdriver as a lever, unlatch
the fuse holder in the AC inlet and remove it.
3.) Remove the voltage selection insert and ro-
tate until the new nominal mains voltage level indication
(115 or 230) is on top and properly oriented for reading.
4.) Replace the voltage selection insert in the AC
inlet, making sure that it is plugged in all the way.
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