Dual High Gain Line Amplifiers

Ideal Use Cases

The RDL STA-2A is designed for line-level audio paths that need added gain, stronger line-driving capability, or conversion between different signal formats and impedances. Its two identical circuits can operate as a stereo pair or as two independent mono channels. Each channel accepts a 20 kΩ balanced or unbalanced input and provides either a 150 Ω balanced output or a 75 Ω unbalanced output. This combination suits level matching, balanced-to-unbalanced or unbalanced-to-balanced conversion, and high-to-low impedance conversion. The adjustable gain range extends from -14 dB through unity to +24 dB, supporting both attenuation and substantial amplification within one dual-channel unit.

Why Choose This Model

Choose this model when a fixed-gain interface does not provide enough control. The STA-2A combines dual-channel line-level preamplification with low-impedance, high-current line drivers. Balanced output is +4 dBu nominal, while unbalanced output operates 6 dB below the balanced line level. Maximum input level is +24 dBu, and maximum output reaches +25 dBu. More than 20 dB of headroom above +4 dBu provides additional operating margin under the published conditions. Its functions are concentrated on audio-line gain, format conversion, impedance conversion, and output drive.

Installation and Integration

The two circuits may be assigned to left and right channels or to separate mono sources. Select balanced or unbalanced operation to match the connected source and destination. The 20 kΩ inputs accommodate either format; output impedance is 150 Ω balanced or 75 Ω unbalanced. For systems referenced to a +4 dBu nominal balanced level, the listed input-signal specification for +4 dBu output spans 20 dBu (-18 dBV) to +18 dBu as supplied in the source data. Adjustable gain allows each channel level to be configured for the required conversion or drive task.

Power requires 24 Vdc at 50 mA and supports a ground-referenced or floating configuration through the RDL SupplyFlex™ power input configuration. The recommended supply is the PS-24AS for the USA or PS-24AX for international use, and it is not included. The specified ambient operating range is 0°C to 55°C.

Performance Highlights

Frequency response is 10 Hz to 100 kHz within ±0.05 dB. At unity gain, THD+N is below 0.004%, and IMD is below 0.005%. Noise below +4 dBu is specified at less than -90 dB at unity gain, while crosstalk is less than -80 dB at unity gain. Common-mode rejection is greater than 60 dB from 50 Hz to 120 Hz. Together, these published measurements define a wideband, low-distortion signal path with strong channel separation under the stated test conditions.

The amplifier’s +25 dBu maximum output, +24 dBu maximum input, and more than 20 dB of headroom above +4 dBu define its level-handling capability. Its adjustable -14 dB to +24 dB range allows the required attenuation or gain to be set for each channel.

What Makes It Different

The distinguishing combination is its pair of identical channels, adjustable attenuation or gain, balanced or unbalanced interfacing, and high-to-low impedance conversion. It can serve as a dual line-level preamplifier while also providing the low-impedance, high-current output behavior specified for line driving. Each channel uses the same published electrical limits, keeping stereo and dual-mono system planning consistent. RDL’s SupplyFlex power input adds the choice of ground-referenced or floating 24 Vdc operation. These capabilities place gain adjustment, connection-format conversion, impedance conversion, and output driving in the same model.

Final Assessment

The RDL STA-2A is a focused two-channel solution for audio lines requiring up to 24 dB of gain, balanced or unbalanced conversion, and low-impedance output drive. Its 10 Hz to 100 kHz response, low published distortion at unity gain, +25 dBu maximum output, and stereo or dual-mono flexibility provide a clearly defined performance envelope. It is best matched to systems that need controlled line-level amplification or signal-format conversion and can provide the required 24 Vdc power. A recommended power supply must be purchased separately.