Line-Level Audio Switch-2x1

The RDL ST-SSR1 is a compact 2×1 audio switcher designed for balanced, line-level signal routing. It accepts two +4 dBu nominal inputs and sends the selected signal to one balanced +4 dBu nominal output. The unit can switch between two sources or serve as a silent on/off switch for a single audio channel.

Ideal Use Cases

The ST-SSR1 is suited to systems that need simple, externally controlled selection between two balanced audio sources. One source connects to the NORMAL input and another to the SELECT input. Without a grounded trigger, NORMAL feeds the output; grounding the TRIG terminal routes SELECT to the output. This operating arrangement supports source selection in installed audio systems, automated signal paths, and applications requiring remote switching. When used with a single channel, the unit can also provide silent on/off control.

Why Choose This Model

Each of the two balanced inputs has a 20 kΩ impedance and a +4 dBu nominal level. The balanced output is rated at +4 dBu nominal with a 150 Ω impedance and uses a terminal-block connection. ON gain is unity with a 600 Ω balanced input and output, allowing the selected signal to pass without a specified gain change. Two LEDs provide immediate status confirmation: the left LED identifies the NORMAL input as active, while the right LED identifies the SELECT input.

Installation and Integration

Connect the primary balanced source to NORMAL, the alternate source to SELECT, and the destination equipment to the balanced output. Selection is controlled by externally pulling the TRIG terminal to ground. The specified control current is only 0.5 mA, and the supplied product information indicates that control may come from sources ranging from switches to logic circuits. The ST-SSR1 requires ground-referenced 24 Vdc power at 40 mA. The recommended power supplies are the PS-24AS for the USA and the PS-24AX for international use; a power supply is not included. Its specified ambient operating range is 0°C to 55°C.

Performance Highlights

The ST-SSR1 supports fast and soft switching modes. Timing values are specified in fast/soft order: the NORMAL input turns off in 10 µs/5 ms and turns on in 15 µs/70 ms. The SELECT input turns off in 15 µs/10 ms and turns on in 20 µs/35 ms. Frequency response is 15 Hz to 20 kHz within ±0.5 dB with a bridging load, or 30 Hz to 20 kHz within ±0.5 dB with a 600 Ω load. THD+N is less than 0.05%, while noise below +4 dBu is specified at less than -80 dB, with 85 dB typical. Headroom above +4 dBu exceeds 18 dB. CMRR exceeds 45 dB at 100 Hz on either port, and OFF attenuation exceeds 80 dB from 10 Hz to 20 kHz on either input.

What Makes It Different

The ST-SSR1 combines balanced 2×1 routing, selectable fast or soft transition behavior, and low-current external control in one compact switcher. Its default NORMAL path and ground-triggered SELECT path make the switching state easy to define within a control design. Unlike a switcher that provides only source routing, this model can also be applied as a silent single-channel on/off control. Dedicated active-input LEDs keep its current routing state visible during setup, operation, and troubleshooting.

Final Assessment

For balanced +4 dBu systems requiring two-input selection or controlled single-channel muting, the RDL ST-SSR1 provides a clearly specified signal path and straightforward trigger behavior. Unity ON gain, greater than 80 dB OFF attenuation, fast and soft switching options, and visible input-status indicators make it a focused choice for line-level audio routing. Integration requires a ground-referenced 24 Vdc supply and an external ground control for the TRIG terminal.