We suggest that you either use test complexes (like Audio Precision) or download a good measuring software (for example, trial version of SpectraPLUS-SC). You will need to make precise measurements of THD and frequency curves and these tools will be very useful.
If assembled properly, the 73EQ module should work without any adjustments.
Here is our suggested procedure for testing the unit:
- Make sure the EQ switch is disengaged (levers down).
- Apply power and check for module power LED to illuminate.
- Inject 1 kHz test tone to the input of the 1290 unit. Make sure the unit is passing clean and not distorted audio.
- Inject white noise test tone to the input of the 1290 unit. Put spectrum analyzer at the output and make sure that it shows flat line from 20 Hz to 20 kHz.
- Engage the EQ switch and check equaliser controls. It is convenient to observe resulting frequency curve on the analyzer. Check that all frequencies marked on the front panel coincide with center frequencies on the analyzer. Check that equalizer boost and cut ranges are up to specs (+/-16 dB for shelf filters and +/- 18 dB for bell filter).
- Check that high-pass filter is working up to specs.
Finally, put all the knobs on the potentiometers and rotary switches.
Enjoy your 73EQ module!