ALLEN & HEATH DR128 User's Guide download pdf (Page 19)

DR66 & DR128 Installer User Guide 19

Labelling the Function Keys

DR66 Write-on blocks are provided above each of the 8 function keys. Use permanent pen or

pre-prepared adhesive labels to identify the key functions. A log sheet to keep a record of the

functions is provided at the rear of this user guide.

DR128 The front panel facia plate can be removed so that a label can be fitted behind the

window above the 12 function keys. This ensures that the key identification is tamperproof. Use a

2mm hex key to remove the four corner hex fixing screws. This can be done with the unit installed

in its rack or furniture. A Windows

Word

template is provided with the WinDR software. It is

also printed together with fitting instructions and installer log sheet at the rear of this user guide.

Working with Audio Signal Levels

When calibrating the unit it is advised to have a PC running WinDR so that you can use the full

range channel meters to set the optimum input and output operating levels. These are high

resolution dBFS bar meters that display signal up to maximum output level. Alternatively, the front

panel LED indicators could be assigned as input or output level meters to show basic signal

presence, nominal level and peak.

0dBFS 0dB Full Scale is the maximum internal signal level before clipping. To avoid distortion

the signal that is passed through the ADC and DAC should not exceed this maximum. For this

reason calibration trimmers are provided to match the source to the DR input stage, and to match

its output to the destination equipment.

While the dynamic range is the signal capability from noise floor to clipping level, the signal-to-

noise performance is determined by the nominal (normal) operating level. The higher you make

this level the better the noise performance but the less the headroom. It is typical to provide at

least 10dB of headroom above the nominal level to allow for unexpected signal peaks and loud

moments. The DR front panel meters (if assigned) are calibrated for a nominal level allowing 12dB

of headroom. Of course, you can operate the unit at lower or higher level if you wish to allow more

or less headroom. It is important that the relationship between the internal 0dBFS and the output

dBu level is understood.

Meter Green Meter Amber Meter Red

Signal presence Nominal level Signal peak

Channel active Normal loud Approaching clipping

-36dBFS -12dBFS -6dBFS

Operating

Level

Output

Setting

Meter

Green

Meter

Amber

Meter

Red

Clip Headroom

-10dBV (-8dBu) -10 -32dBu -8dBu -2dBu +4dBu 12dB

0dBu 0 -24dBu 0dBu +6dBu +12dBu 12dB

0dBu +4 -20dBu +4dBu +10dBu +16dBu 16dB

+4dBu +4 -20dBu +4dBu +10dBu +16dBu 12dB

1 2 ... 14 15 16 17 18 19 20 21 22 23 24 ... 43 44

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ALLEN & HEATH DR128 User's Guide Page 19

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