Specifications

CX335 Technical Manual Page 17
Removal of the smaller display Printed Circuit Board should only be necessary if there is
a display fault. Viewing the unit from above, remove the 2 M3 machine screws to free the
display board from the supporting pillars. Take care not to strain the jumper cable.
Audio Calibration
Internal adjustments of the CX335 will not need any attention. However if component
changes have been made, it may be necessary to adjust one or more of the pre-set
potentiometers. To adjust the presets you will require an adjustable level, balanced test
sine wave signal of two differing frequencies, we suggest 100Hz and 1kHz, initially set to
a line level of +0dBu (0.775V RMS). You will also require an accurate VU measuring
meter (with adjustable, or automatic, gain make-up) and an oscilloscope.
Static testing - where all levels can be measured.
9.01
The front panel of the unit must be initially adjusted as follows:-
Both Slow and Hard switches released. (Out).
Compressor Threshold rotated fully Counter Clockwise to '+10dB'.
Compressor Ratio rotated fully Counter Clockwise to '1.2:1'.
Peak Level setting rotated fully Clockwise to '+26dB'.
Output Gain set initially to '0dB'. (In its detent).
Bypass / Normal initially set to 'Bypass'. (In).
The following series of tests will ensure all the features of the CX335 are operating
correctly. In most cases, the conditions for each test should be continued into the
following test. Consequently, it is suggested that all tests should be carried out in the
numbered sequence.
9.02
Due to the fact that many of the internal presets and front panel controls are referenced to
the voltage supply rails, it is prudent if the actual voltages and condition of the rails are
measured. The outputs of the regulator IC31 (LM317) should be at +15 Volts and
regulator IC32 (LM337) -15 Volts. Any discrepancy from these voltages should be equally
balanced when compared to ground, ±0.25 Volts. A difference of greater than 0.5 Volts
may cause some presets to have insufficient range.
Ensure no noise or RF interference is present on either rail.
Also, ensure that the input to IC14a pin3 does not have any positive offset voltage; a
negative offset of no more than 100mV is better. The closer to 0Volts this point measures,
the easier calibration will be.
9.03
Insert a 1KHz +0dBu balanced test signal into both channels. With the Bypass switch
pressed in, ensure that the LED meters up to the 0dB LED, just illuminates. If one (or
both) doesn't, try increasing the input test signal level by no more than 0.3dB. If the 0dB
LED still doesn't illuminate then rectify the fault in the display circuit(s). Re-select 'Normal'
operation. Increase the Gain control fully clockwise until the +12dB LEDs illuminates. (All
the LEDS in the meter should be illuminated at this point). Similarly decrease the control
observing a linear decrease in both meters
9.04
0dB (set true zero dBu, presets marked PR2 for the left channel and PR4 for the right
channel) With bypass depressed, ensure that 1KHz 0dBu is input to both channels and
0dB can be measured at both outputs. Ensure that the Gain control is centralised in its
detent. Release the bypass switch and observe 0dBu signal at both outputs. Adjust the
respective preset to correct any discrepancy in either or both channels.