Crown FM600 - Audio Processor Adjustments; Stereo Generator Adjustments

5.1 Audio Processor Adjustments
5.1.1 Pre-Emphasis Selection
Select the pre-emphasis curve (75 µsec, 50 µsec, 25 µsec, or Flat) by jumpering the appropri-
ate pins of header HD1 on the audio processor/stereo generator board. (See section 2.10.) If
you change the pre-emphasis, change the de-emphasis jumpers, HD201 and HD202 on the
audio processor/stereo generator board, to match. (See section 2.10.)
5.1.2 Pre-Emphasis Fine Adjustment
Trim potentiometers, R23 and R63, (for left and right channels, respectively) provide for fine
adjustment of the pre-emphasis. Set the potentiometers to bring the de-emphasized gain at 10
kHz equal to that of 400 Hz. (At the proper setting, 15.0 kHz will be down about 0.7 dB.)
When making these adjustments, it is important that you keep signal levels below the proces-
sor gain-control threshold.
A preferred method is to use a precision de-emphasis network in front of the audio input.
Then, use the non-de-emphasized (flat) output from the FM modulation monitor for measure-
ments.
5.2 Stereo Generator Adjustments
5.2.1 Separation
Feed a 400–Hz sine wave into one channel for at least 70% modulation. Observe the classic
single-channel composite stereo waveform at TP1 in the RF Exciter circuit of the Motherboard.
Adjust the Separation control R244 for a straight centerline.
Since proper adjustment of this control coincides with best stereo separation, use an FM moni-
tor to make or confirm the adjustment.
5-2 FM600 User’s Manual