Description
The ST-UMX3 is a compact 3×1 universal audio mixer designed to combine three mic-level or line-level signals to a single output. It provides switch-selectable MIC/LINE settings on each input and a separate MIC/LINE switch for the output – enabling flexible level matching. The unit includes isolated input preamplifiers and individual gain controls for precise level setting.
Each input has a dedicated preamplifier with a single-turn audio taper gain control for smooth adjustment. Signals from the three preamps are actively summed and delivered to the output amplifier which includes an RDL dual-LED VU meter for visual level monitoring. The dual-LED meter follows standard VU ballistics and provides clear green/red indication from -11 dBu to +4 dBu.
Performance specifications include very low distortion and wide frequency response to preserve audio fidelity. THD+N is rated at < 0.006% and IMD is < 0.04% for mic gain and < 0.008% for line. Frequency response extends to 100 kHz with tight tolerances, and each channel offers substantial gain range and headroom for demanding signals.
The ST-UMX3 supports balanced and unbalanced connections and presents input impedances optimized for microphone and line sources. Input impedance is 600 Ohm for mic mode and 50 kOhm balanced in line mode, while outputs are 150 Ohm balanced and 75 Ohm unbalanced. Note that mic inputs are not protected against phantom voltage – RDL ST-MPA24 or ST-MPA48 adapters are recommended for phantom-powered microphones.
This mixer is suited to broadcast, installed audio, and production workflows where compact summing of discrete sources is required. It can be used to add additional mic or line inputs to an existing system, combine different level or impedance sources, or feed a single downstream processor or recorder. The combination of selectable input/output levels and low-noise preamps makes it appropriate for field racks and permanent installs alike.
Setup and operation are straightforward with front-panel gain controls and the integrated dual-LED VU meter for level setting. The unit requires a ground-referenced 24 Vdc supply at 55 mA and is specified to operate in typical ambient environments. Built for reliable operation, the ST-UMX3 provides clear level control, isolation, and visual metering in a compact package.