Altec Lansing 4200A - Manual (Page 8)

8
Operating Manual 6125A and 4200A Multi-Channel Power Amplifier
7.5 Input Level Controls
Input Level Controls attenuate input signal from
0dB down to -
∞
. For best performance, Altec recommends
that the level controls be operated at full level (0 dB at-
tenuation).
In STEREO mode, each level control corresponds
directly to the input signal on its respective channel.
In MONO Mode, the input signal connected to
channels 1, 3, or 5 are used to drive channels 2, 4, or 6
respectively, and the level controls for channels 1, 3, and
5 likewise control channels 2, 4, and 6. When switched to
Mono mode, channels 2, 4, or 6 level controls become in-
active.
In BRIDGED mode, the level controls function
the same as in mono mode.
7.6 Stereo/Mono Switch
The 6125A is comprised of three stereo amplifi-
ers (two on the 4200A), each operating independently of
the others, with Stereo/Mono switching available for each
channel pair. If this switch is set to Stereo mode, the chan-
nel pair operates as two discrete amplifiers, each with its
own input connection and level control.
Switching to Mono mode allows one input (chan-
nel 1, 3, or 5) to drive both channels of a stereo channel
pair. Pressing the Mono switch disables the channel pair's
other input connection, as well as its level control. The
first channel's input and level control now determines the
signal to both channels.
7.7 Dual Channel/Bridge Mode Switch
Bridging a power amplifier is the process whereby
two channels are supplied the same signal, with the sec-
ond channel's phase inverted 180°. The speaker is then
connected across the (+) output connections of each chan-
nel, resulting in twice the power to the speaker that either
channel could deliver by itself. Since in Bridge Mode both
connections have voltage present, never connect or touch
either speaker wire to ground.
The 6125A is capable of three channels of bridged
output (two channels on the 4200A). To use bridged mode,
first press MONO from the Stereo/Mono switch on the
channel pair to be bridged. This sends the same audio
signal to both channels. Then press BRIDGE from the
Dual/Bridge switch on the channel pair to be bridged. This
inverts the phase of the input signal to the second channel.
These two channels are now operating together in Bridged
Mono mode, and the output must be taken from the two
(+) terminals of the corresponding bridged channel pair
7.8 Loudspeaker Output Connectors
Three terminal blocks (two on the 4200A) pro-
vide connections for the speaker outputs. In BRIDGE
mode, the channel 1, 3, or 5 (+) connection is the Bridged
(+) speaker output terminal, and the channel 2, 4, or 6 (+)
connection is the Bridged (-) speaker output.
CAUTION! NEVER CONNECT THE TWO
BRIDGED OUTPUTS TOGETHER OR CONNECT
EITHER BRIDGED OUTPUT TO GROUND.
Model 6125A
shown.
Model 4200A
has only four
channels.