SONOSAX SX-PR (by Gary J. Louie) - Manual (Page 6)

using disposable batteries, or they will leak or explode when external power is applied.
To access the jumper, remove the four Phillips screws on the bottom of the master
module. Remove the battery compartment/DC to DC converter assembly by pulling
straight up. A copper shield surrounds this assembly, and should come up with it. When
the assembly is removed, invert and remove the copper shield. Adjust the CHARGING
JUMPER J10 on this circuit board. Leave the jumper on both pins 1 and 2 for the
connected mode (for rechargeable cells). Hang the jumper on one pin only to disconnect
(for disposable cells).
Modulometer characteristic, peak or VU (factory set to peak). Selector switch accessible
from the left side of the module.
Modulometer pre or post headphone monitor (factory set to pre). Selector switch
accessible from the left side of the module.
Limiter activation level, left and right (factory set to 0 dB on the modulometer = +6 dBu at
the output = 1.55 volts). Trim pots accessible from the left side of the module.
Tape return level, left and right (factory set to 0 dB = +6 dBu = 1.55 volts). Trim pots
accessible from the right side of the module.
Main output CMRR adjustment, left and right. Equalizes the amplitude of the differential
signal conductors for optimum Common Mode Rejection Ratio performance. Requires
partial disassembly of the master module to access the adjustment screws.
To access the CMRR trimpots, separate the master module from other modules. Undo
the four Phillips head screws on the bottom, which holds the battery compartment and
DC to DC converter. Remove the battery compartment/converter assembly by pulling
straight up. Undo all fasteners on the back panel, including two 2mm hex screws on
each XLR output connector, the 1/2 inch nut on the headphone jack, the external power
jack nut, and two nuts holding the accessory connector. The back/bottom extrusion may
be eased off. USE EXTREME CARE not to stress the circuit board, which is extremely
narrow at each side and is now unsupported. Reattach the battery compartment/
converter assembly. Being careful not to allow exposed leads to touch, apply power to
the mixer and switch it on. Activate the internal oscillator and turn the master level
controls up to a nominal 0 dB. Connect probes from a dual channel oscilloscope to the
balanced audio leads of one output connector (pins 2 and 3). Set the scope to ADD
mode, and set the sensitivity the same for each channel. If the two balanced leads are
exactly balanced, they should cancel out perfectly since they should be exactly the
same, but 180 degrees out of phase. Adjust the potentiometer until best results
(maximum cancellation) are achieved. Trim pot T3 is for the left channel and is nearest
the battery compartment. T4 is for the right channel.
Gary Louie/Staff Audio Engineer
Univ. of Washington School of Music/Seattle, Washington USA
Internet: [email protected]
Visit Gary's Home Page...
Gary Louie (University of Washington)
This site includes AES Pacific Northwest News.