ABSTRACT
Figure 4.10.2 shows a stylised diagram of a mixer’s input module. The signal path starts with input selection and format conversion. The mixer may have to handle various analogue signals (microphone level, unbalanced and balanced line level) and digital formats (including standard and proprietary signals), and these have to be converted to the mixer’s internal processing standard. The input section commonly features gain controls (pre-
amplifier to amplify microphones signals and a Pad switch to attenuate high level line signals) and phase reversal. Input impedance is normally switched between 1 k ohms for microphones and 10 k ohms for line level sources. Digital mixers are likely to feature ADCs (analogue-to-digital converters), digital sample rate and format converters. Often, external patch bays and format converters are built into the mixer chassis to provide additional signal management before interfacing the input module. In the case of some digital sound mixers, an integrated input router provides ‘digital patching’ and format conversion.
4.10.1.2 Input channel processing
