A high-end, CLASS-A output amp that offers the basic features required in a smaller mixer configuration. Adding the optional AUX master unit provides all routings plus further output functions. The two L / R master faders attenuate or amplify the L and R signals from all input units. Resulting signals can be seen on the VU meters. These show the amount of signal being sent to the XLR output connectors (LEFT OUT and RIGHT OUT) and onwards to other audio devices, or a PA system. Note: Arthur features a headroom of 30 dB, so its electronics and output amps are rarely likely to clip. The purpose of the VU meters, therefore, is mainly to monitor the level of signal flow to successive audio devices. The ON/OFF buttons connect faders with output amps. These are similar to the MUTE buttons used on other mixers, but their functionality is reversed. When the ON/OFF buttons are depressed, the L and/or R outputs are connected (whereas a MUTE button disconnects the output in its depressed position). The L /R master unit also has a single AUX send and FX return, enabling the connection of a reverb unit. Note: With larger mixers, the reverb / effects unit is probably connected to an additional stereo input unit, where frequency corrections and routings such as "reverb to monitors" can easily be set. This isn't possible in a basic "all through one L / R master unit" configuration. The reverb unit's input will be connected to the AUX 1 OUT and its output to the FX RET (effect return). This enables the amount of reverb for every input unit (for example the mic units) to be controlled via the AUX 1 knob. This must be set to "post-fade" (orange light on the post/pre button), making the reverb amount dependent on the channel fader position. The FX RET fader controls the amount of reverb mixed in (in the same proportion) to the Left and Right signals on the L/R master output. The L/R master unit also features a switch (positioned on the circuit board) that deactivates the summing function of its AUX 1 section. Changing this switch from its default setting (AUX 1 on) to AUX 1 off means that AUX 1 on the L/R master unit stops running and the reverb unit "takes over" the AUX 1 signals from all channels. The summed AUX 1 signal from the reverb unit can however be picked up for external use. The mixer’s power supply is connected to the DC IN connector. From this 48 Volt DC input, all other units attached to the L/R master unit will also be served via this power supply. For more information on available power supplies, maximum unit numbers etc, please consult the manual. (Chapter: Power Supply and Starting the Mixing Console.) Combining L/R master units: The Arthur concept enables the combination of a quasi-infinite number of outputs, which can prove useful in a range of situations. The mixer's structure only allows for one summing amp, which will sum all L and R signals coming from the BUS. The L/R master unit features a switch - positioned on the circuit board - to deactivate that summing function. If more than one L / R master unit is used, only one unit should be left as per its default setting (i.e. with summing on). All additional L/R master units must be switched from their default settings to "summing off". If using the Master EQ unit together with the L/R master units, this unit will do the "summing job". In this case, all L/R master units on the mixer must be switched to "summing off", even if there is only one L/R master unit involved. For more information, please consult the manual. (Chapter: Master EQ Unit)