Ramsey Electronics UAM4SYS Assembly And Instruction Manual page 10

The 'GAIN' jumpers, H4 and H5, are used to adjust the gain of the MAX9708.
See the tables on the schematic for specific settings. The gain settings are
also printed on the UAM4SYS circuit board next to the jumpers.
The 'MUTE' input terminal located below the left and right channel inputs is
used to place the UAM4SYSinto the mute mode. The mute mode causes the
output transistors to stop switching. This may be used to silence the
UAM4SYS with the advantage of a built in click/pop suppression feature of the
MAX9708. Shutdown mode reduces the power consumption of the
UAM4SYS to a very low level, about 0.1uA. This is handy for battery operated
applications to increase battery life. The mute function is controlled by the
second half of flip flop IC U5. This circuit operates in exactly like the flip flop
used for the loudness function with the exception that the 'Q' output on pin 10
is connected to the power amplifier, U7 pin 31, instead of controlling an analog
switch. U7 is muted when the 'Q' output is low, 0 volts. Note that the mute
function only controls the output of the speaker output. It will not have any
effect on the headphone or line outputs of the UAM4.
The UAM4SYS may be operated as either a 2 channel, 21 watt per channel,
or a single 42 watt amplifier. The mode of operation is determined by header
jumper H3 and the placement of jumpers at L+, L-, R+ & R- located near the
output terminals. With no jumper installed on H3 the MAX9708 is in 2 channel
or stereo mode. This means that it is operating like two separate amplifiers.
In this mode there should be no jumpers installed at the L+, L-, R+, & R-
points.
DO NOT INSTALL ANY JUMPERS AT L+, L-, R+, & R- WHEN NO JUMPER
IS INSTALLED AT H3
If a jumper is installed at H3 the MAX9708 will operate in mono mode. In this
mode only the signal applied to the right channel input is used. You may use
the UAM4SYS as either a single 42 watt amplifier if are installed between L+
& R+ and between L+ & R-. If jumpers are not installed between L+ & R+,
and between L+ & R-, the UAM4SYS will operate as two 21 amplifiers with the
same input signal.
Note that even though it appears you could connect the left and right speaker
outputs together at a point away from the UAM4SYS
DO NOT ATTEMPT THIS!!!
Connections away from the board may cause signal phasing differences and cause
damage to your UAM4SYS.
UAM4SYS • 10