Audio Distribution Amplifier-Balanced/Unbalanced-2×4, 1×8

The RDL RU-ADA4D is a four-channel stereo audio distribution amplifier with a flexible 2×4 or 1×8 signal path. In stereo operation, inputs A/left and B/right feed four corresponding A/B output pairs. A rear-panel mono selector allows input A to feed all eight outputs. The unit accommodates balanced +4 dBu and unbalanced -10 dBV signals, with input gain controls, individual output-level adjustments, and dual-LED input metering.

Ideal Use Cases

The RU-ADA4D fits systems that need one stereo source distributed to four destinations while retaining separate left and right channels. It also addresses one-input/eight-output distribution requirements: selecting mono mode routes input A to every output. Support for both balanced and unbalanced operation allows the amplifier to connect equipment using nominal +4 dBu balanced levels or -10 dBV unbalanced levels. Eight separate output adjustments are useful when each destination requires an independently set level rather than one shared output setting.

Why Choose This Model

Two input-gain adjustments and eight output-level adjustments provide control at both stages of the distribution path. Dual-LED VU metering monitors input A and input B, giving a direct indication of incoming signal levels. The nominal balanced input level is +4 dBu, with a specified maximum of +25 dBu. Balanced outputs operate at a nominal +4 dBu and support a maximum output level of +24 dBu. Unbalanced input and output operation is specified at -10 dBV.

Installation and Integration

The two stereo inputs are presented as A/left and B/right connections on a detachable terminal block. The eight outputs are arranged as four A and four B connections on detachable terminal blocks. Input impedance is 20 kΩ balanced or 10 kΩ unbalanced, while output impedance is 150 Ω balanced or 75 Ω unbalanced. The case measures 5.75 inches wide by 1.65 inches high by 3.54 inches deep, increasing to 3.9 inches deep with connectors. Power requirements are ground-referenced 24 Vdc at 82 mA idle and nominal, or 120 mA maximum. Recommended power-supply models are the PS-24AS for the USA and PS-24AX for international use. The specified ambient operating range is 0° C to 50° C.

Performance Highlights

Frequency response is specified from 10 Hz to 165 kHz within ±0.25 dB and from 10 Hz to 35 kHz within ±0.01 dB. THD+N is less than 0.0025% from 20 Hz to 20 kHz. Noise is specified below -92 dB relative to a +4 dBu output across the same 20 Hz to 20 kHz range. Crosstalk is below -90 dB from 20 Hz to 5 kHz and below -80 dB from 5 kHz to 20 kHz. The specified CMRR is greater than 90 dB at 100 Hz, and headroom exceeds 20 dB above a +4 dBu input or output.

What Makes It Different

The defining feature is its selectable distribution structure. One compact unit can operate as a stereo amplifier with four A/B output pairs or as a mono amplifier with eight outputs. Switching modes does not remove individual output control; all eight outputs retain separate level adjustments. The two input adjustments cover 5 dB to +15 dB relative to +4 dBu balanced operation and -3 dB to +17 dB relative to -10 dBV unbalanced operation. Combined with the dual-LED meters, these controls provide specific adjustment points before and after signal distribution.

Final Assessment

The RU-ADA4D is a focused solution for distributing balanced or unbalanced analog audio as either four stereo output pairs or eight mono outputs. Its detachable terminal-block connections, selectable mono routing, two input-gain controls, eight output-level controls, and input metering provide a clearly defined integration workflow. Wide specified frequency response, low THD+N, greater than 20 dB of headroom, and compact case dimensions complete its practical distribution capabilities.