Dual functionality. GRP/Aux mode switches reverse aux faders with the group and L&R faders giving up to 10 monitor sends with inserts on 100mm faders. A Centre Mode switch converts the 100mm C fader to engineer’s listen wedge control with insert
Formats: 24, 32 or 40 channels – either all mono or with 8 stereo channels. Was also available part-loaded. Meterbridges were optional
8 Audio groups. Assigned from paired routing buttons and pan from channels. Groups access LR & M busses and have XLR outputs with insert. Groups have 3 segment led pre-fade meters and 12 segment, 3 colour peak reading meter access, plus VU meters if meterbridge is fitted
10 auxiliaries switchable pre/post fade in blocks: 1-4, 5-8, 9-10
Left, Right and Mono busses. Available from channels and groups. LR & M have 12 segment, 3 colour peak reading meter access plus VU meters if meterbridge is fitted. GL4 also includes secondary L&R output with level and pre/post fader select on TRS jacks (can swap with the aux 9-10 XLR outs with inserts)
11×2 Matrix. Fed from the groups and the LR & M busses
8 Mute groups. 8 master mute group buttons with single / multi mode and preview facility. Input channels, auxes, groups and LRM sections all have mute buttons
4 band EQ plus HPF. Separate controls for sweep and cut/boost on all sections. HPF is swept from off-20-400 Hz
Stereo channels. GL4 could be ordered with blocks of 8 stereo channels, each with individual gain input stages for left and right sources
PAFL system. Stereo PFL with trim
Talkback. Talk to LRM, groups and auxes. Trim control for mic
Lamps. 2 BNC lamp sockets are provided
PSU. The GL4 was supplied with a RPS10 rack mounting (3U) linear power supply. A backup RPS10 could be linked via an RPSD power supply combiner and auto-switcher