Extron electronic DMP 64 manual Optimizing Audio Levels, b c d, Gain, Trim and Volume Controls

Optimizing Audio Levels

The DMP 64 uses floating point DSP technology, processing data using a combination of 32- and 64-bit algorithms. The analog to digital converters (ADC) and digital to analog converters (DAC) sample at 48 kHz with 24-bit resolution.

With floating point DSP it is extremely difficult to clip the audio signal within the DSP audio signal chain, after the ADC input and before the DAC output. That means the audio signal must not be clipped at the input ADC. Clipping gives audibly undesirable results and once the audio is clipped at the input there is no way to correct it further down the signal chain. If audio clipping occurs at the output DAC that is not a result of clipping at the input ADC, there are ways to address it within the DSP audio signal chain.

The meters in the DSP Configurator indicate clipping at a user-definable point, with the default setting at –1 dB. This means the meter indicates clipping when it reaches –1 dBFS, or 1 dB below actual clipping (0 dBFS). Setting the clipping meter below clipping provides a “safety net”, allowing the user to reduce input gain before clipping actually occurs. This safety net can be increased or decreased by selecting Tools>Options>Processor Defaults>Defaults>Meter Clipping, and setting the Clip Threshold to a number between 0 (dB) and – 20 (dB).

NOTE: When the Clip Threshold is set to 0 (dB), clipping is indicated only when clipping occurs.

Meters within the DSP Configurator are peak-type meters, referenced to full scale, or

0 dBFS. For the DMP 64 outputs, 0 dBFS corresponds to +21 dBu, the maximum output level of the device. Maximum input level is +24 dBu. Gain from – 3 dB to +80 dB is applied in the analog domain, while attenuation from – 3 dB to –18 dB is applied in the digital domain. The input meters are post-ADC, while the output meters are pre-DAC.

The remainder of this section will reference the gain, trim and volume controls outlined in figure 58 below.

a b c d e

Figure 58. Gain, Trim and Volume Controls

A Mic/Line input gain	D
B Pre-mixer gain	E
C Mix-point gain

Post-mixer trim

Output volume

DMP 64 • Software Control 88