Ramsey Electronics UAM4 Manual page 7

and below the input connections call 'INPUT MODE'. This is a jumper, H3,
used to set up for either stereo or mono mode. If is not installed the UAM4 will
be in stereo mode. The left and right channels are independent and operate
as two separate amplifiers. If the jumper, H3, is installed the UAM4 will
operate in mono mode. Only the signal applied to the right channel input will
be used and the left and right outputs will be identical. They can be used as
either two 20 watt amplifier outputs and used to drive two separate speakers
or you may also set up the UAM4 to operate as a 40 watt amplifier when
mono mode is selected. This is done by placing jumpers between the 'L+' and
'R+' and between 'L-' and 'R-' jumper locations on the board just below the
speaker output terminals. These jumper points are located near the upper
right corner of the MAX9708 in the schematic. In this configuration the left
and right output terminals are connected in parallel and may be used to drive
one speaker at a power level of 40 watts. It is important to note that you NOT
simply connect the left and right speaker terminals together, either at the
terminals or any other point other than the jumper points on the board. Doing
so may cause nasty things to happen due to the output switching frequency
and the length of wire between the output and remote connection point. Use
only the on-board jumpers for this configuration
The 'GAIN' jumpers, H4 and H5, are used to adjust the gain of the UAM4.
Below the 'GAIN' jumpers is the 'THERMAL THRESHOLD' jumpers, H6, H7
and H8. These set up the temperature at which the actual chip in the
MAX9708 will cause the device to go into a shutdown mode. Basically if the
MAX9708 gets too hot it will automatically shut itself off. The signal on pin
#32 of the MAX9708 is used to turn on transistor Q1 and light the LED, D1,
when the temperature set by these jumpers is reached. This signal may also
be used to place the UAM4 into either 'MUTE' or 'SHUTDOWN' mode when
an over temperature condition occurs.
The 'AUTO SHUTDOWN' jumper H9 to the left of the 'GAIN' jumpers is used
to select if the over temperature described above that will cause the MAX9708
to go into mute or shutdown mode. If no jumper is installed on H9 then the
over temperature condition will simply turn off the MAX9708 output transistors
internally.
The 'MUTE' and "SHUTDOWN' input terminals located below the left and right
channel inputs may be used to place the UAM4 into the indicated mode. The
mute mode causes the output transistors to stop switching. This may be used
to silence the UAM4 with the advantage of a built in click/pop suppression
feature of the MAX9708. Shutdown mode reduces the power consumption of
the UAM4 to a very low level, about 0.1uA. This is handy for battery operated
applications to increase battery life. Both of these input controls are logic level
signals and are pulled to a level of 7.5 volts supplied on the UAM4 board by
zener diode, D1, and resistor R7 which can be found in the lower left corner of
the schematic. By connecting the respective pins to ground the mode is
UAM4• 7