Operating Notes; Operating Level; Grounding; Crossover Filter Slopes - PROEL DSO26 User Manual

DSO26 User Manual

OPERATING NOTES

Operating Level

With any audio signal processing equipment it is necessary to ensure adequate signal
level is used through the device, to avoid sacrificing noise performance. With equalisation
in use it may be necessary to reduce the input level, as gain within the unit may cause
digital clipping, indicated by the top red LED's lighting independently of the rest of the
meter.
It should be noted that the figure quoted for the maximum input level options is the clipping
point for that option (not a safe operating level). Always ensure that this clipping point is no
lower than that for the following equipment in the signal chain, and allow extra margin if
equalisation sections are boosted.

Grounding

The Screen (shield) pins on all audio connectors are normally connected directly to the
ground pin of the IEC mains inlet. The chassis is also directly connected to this pin.
Never operate this unit without the mains safety ground connected. Signal ground (0V) is
in turn connected to the chassis ground.
To avoid ground loops, cable shields should be connected to ground at one end only. The
normal convention is that the shield is only connected at the output XLR.

Crossover Filter Slopes

Please consult the block diagrams on page 12 for details of the various configurations
available. All crossover modes feature adjustable crossover frequencies with a choice of
slopes, 5 bands of driver compensation E.Q. per output and delay time plus limiters for
each output. A powerful 8 band parametric equaliser is also provided on each input for
room equalisation. Phase reverse is provided for each output.
A choice of Bessel or Butterworth slopes at 12/18/24dB per octave and Linkwitz-Riley at
24dB per octave are provided. Since Low and High pass functions are separately
adjusted, asymmetric slopes are easily achieved, if required. It should also be noted that
the turnover frequency displayed on the DSO26 is the -3dB point for all slopes except
24dB Linkwitz-Riley where the -6dB point is shown. If the -6dB point is to be used for the
Bessel or Butterworth filter, take the required crossover frequency, multiply this by the
appropriate factor from the following table and then select the closest available frequency
on the DSO26's display.
Filter Type
Bessel 12dB/Oct.
Butterworth 12dB/Oct.
Bessel 18dB/Oct.
Butterworth 18dB/Oct.
Bessel 24dB/Oct.
Butterworth 24dB/Oct.
Please note that unlike conventional analogue crossovers, crossover points and slopes
are set with absolute accuracy since component tolerance problems do not occur.
High pass factors
1.45
1.31
1.37
1.19
1.35
1.15
32
Low pass factors
0.69
0.76
0.73
0.84
0.74
0.87