172.3 Ensuring Proper CoolingWhen using an equipment rack, keep a minimum space of 4 inches (10cm) from thetop surface of the unit. Close any open spaces in the rack with blank panels. DONOT block any air vents. The side walls of the rack should be a minimum of 2 inches(5 cm) from the amplifier sides. The back of the rack should be open.2.4 Choosing Input Wire and ConnectorsWe recommend using pre-built or professionally wired balanced line (two-conductorplus shield) 22-24 gauge cables to connect the amplifier balanced input by using theincluded Euroblock connectors, see Figure 2.4. Unbalanced lines may be used, butmay result in hum or RF noise very long cable runs.You can also use RCA connectors to connect audio devices, for example, CD/DVDplayer. However, do not use both Euroblock and RCA audio input connectors on asingle channel at the same time.NOTE: Custom wiring should only be performed by qualified personnel.MONO SUMAUDIOSOURCEAUDIOSOURCEAUDIOSOURCEAUDIOSOURCEFigure 2.4.1 Input WiringNote: Two RCA connectors are provided for summing left and right channels from astereo source. Do not use both Euroblock and RCA connectors concurrently for anysingle input channel.