Altec Lansing 6125A Stereo Amplifier User Manual


 
7
Operating Manual 6125A and 4200A Multi-Channel Power Amplifier
7. REAR PANEL FEATURES
7.1 Input Connectors
The 6125A and 4200A inputs use balanced two
piece "Euroblock" style connectors. It is recommended
that balanced input connections be used whenever possible
to take full advantage of the amplifier's common mode
rejection properties, and to reduce ground-loop problems.
If a hum problem persists even though balanced inputs are
used, try connecting a balanced signal to the Euroblock
input with the input cable's shield lifted at the amplifier
end of the cable (ie. no ground connection), but connected
to ground at the signal source. This eliminates potential
ground currents through the input cable yet preserves the
benefits of shielding. If connecting an unbalanced signal
to the Euroblock input, connect the signal wire to (+) and
the cable shield to both (-) and ground.
Euroblock
Connector
System
+
-
G
+
-
G
* Model 6125A shown - Model 4200A only
has channels 1-4.
7.2 Input Ground Switch
This switch separates the input signal ground from
the chassis ground on all inputs. Ground connections from
an incoming signal float from the chassis ground when the
switch is out. Unless there are special circumstances which
require the input signal ground and chassis ground to be
disconnected, it is best to leave this switch in.
7.3 Multi-Channel Operation
The 6125A is essentially three stereo amplifiers
in one chassis, for a total of up to six separate channels.
The 4200A is essentially two stereo amplifiers in one chas-
sis, for a total of up to four separate channels. Thus, the
following references to Stereo, Mono, or Bridged opera-
tion is with regard to each of three or two pairs of chan-
nels in the amplifier. For example, Channel 1 and Channel
2 together can provide stereo, mono, or bridged operation,
completely independent of Channels 3-4 or Channels 5-6
settings.
7.4 50Hz Low Cut Switch
Each pair of channels has a 50Hz second order
(12 dB per octave) low-cut filter option which is applied
to both channels within the pair. When the switch is
pressed, the audio signal is -3dB at 50Hz, -15dB at 25 Hz,
-27dB at 12.5Hz, etc.