Gated Line Amplifier-Noise Gate

The RDL ST-GLA1 is a gated line-level preamplifier and noise gate designed to suppress unwanted noise through self-gating. It combines adjustable gain and threshold controls with fast, silent audio switching, integral single-ended noise reduction, flexible balanced or unbalanced connections, and an open-collector logic output. Its specified 10 ms switching time and nominal two-second off delay support controlled transitions between active and muted states.

Ideal Use Cases

The ST-GLA1 is suited to audio paths that should remain muted when the desired signal is absent. Self-gating helps limit unwanted noise from reaching the output, while adjustable threshold control allows the gating response to be set for the connected source. Adjustable ON gain from 45 to 65 dB accommodates applications requiring substantial signal amplification. Balanced or unbalanced input and output compatibility also allows the unit to be incorporated into systems using either connection format.

Why Choose This Model

This model brings preamplification, self-gating, single-ended noise reduction, and logic control together in one device. The audio path switches in 10 ms and is described as silent, helping the gate respond without introducing an intentional switching sound. Its two-second nominal off delay prevents the output from turning off immediately after the signal condition changes. If a longer delay is required, the source data specifies that it may be extended with an external capacitor. The adjustable gain and threshold provide direct control over amplification and gating behavior.

Installation and Integration

The input impedance is 500 Ω when balanced and 5 kΩ when unbalanced. The specified audio output is +4 dBu nominal with a 150 Ω balanced connection on a terminal block. Power requires a ground-referenced 24 Vdc supply at 75 mA. Recommended supplies are the PS-24AS for the USA and the PS-24AX for international use; the power supply is not included. The permitted ambient operating environment is 0° C to 55° C. For control integration, the ST-GLA1 provides an open-collector output rated at 50 mA. These electrical and connection requirements should be matched to the surrounding audio and control equipment during installation.

Performance Highlights

The ST-GLA1 has a frequency response of 15 Hz to 20 kHz, specified within ±0.5 dB when feeding a 10 kΩ bridging input. THD+N is less than 0.030% at 1 kHz, while common-mode rejection is greater than 45 dB. Headroom is greater than 18 dB above +4 dBu. With the preamplifier muted, residual noise is specified at less than -80 dB below +4 dBu, unweighted. Together with the integral noise-reduction function and self-gating operation, these figures define the unit’s behavior across signal amplification, muted operation, and balanced audio use.

What Makes It Different

The defining feature of the ST-GLA1 is the way its adjustable preamplifier works with an internal gate. Rather than providing gain alone, it monitors the signal condition and uses self-gating to suppress unwanted noise. Fast, silent switching manages the audio state, while the adjustable threshold determines gating sensitivity. The nominal off delay can be extended externally, and the 50 mA open-collector output makes the gate state available as a logic output. This combination provides both audio-path control and an associated control signal.

Final Assessment

The RDL ST-GLA1 is a focused solution for systems requiring adjustable amplification and automatic noise gating. Its 45 to 65 dB ON gain range, adjustable threshold, 10 ms switching time, two-second nominal off delay, balanced or unbalanced compatibility, and open-collector control output provide a clearly defined set of audio and integration capabilities. The published frequency response, distortion, headroom, noise, and CMRR specifications make its expected performance straightforward to evaluate before installation.