Automatic Level Control-Stereo-Phono Jacks

The RDL FP-ALC2 is a stereo automatic level controller designed to maintain consistent audio levels when program sources vary. It combines split-band automatic gain control with self-adjusting attack and release times, gated control, and a single user adjustment. Two unbalanced phono inputs and two unbalanced phono outputs support straightforward integration into systems using stereo source equipment.

Ideal Use Cases

The FP-ALC2 is suited to foreground and background sound systems receiving material from sources with inconsistent output levels. Examples provided for this application include multiple CD changers and satellite receivers. When different recordings, channels, or source selections produce noticeable level changes, the controller automatically manages the resulting variation instead of requiring repeated manual adjustments.

Its automatic level operation is particularly relevant where a sound system must reproduce changing program sources at more consistent levels. Gated control helps avoid level seeking, while the split-band AGC is designed to support audio transparency during level correction.

Why Choose This Model

The FP-ALC2 concentrates setup around one gain adjustment. The gain is set as high as possible while playing the loudest source, stopping before the INPUT OVERLOAD indicator flashes. Once that setting is established, no further adjustments are needed according to the supplied product information.

The unit provides a level control range greater than 20 dB and an automatic level range of 30 to 0 dBV. Self-adjusting attack and release times allow the AGC response to adapt without separate timing controls. Split-band processing and gated control address two important operational concerns: maintaining audio transparency and preventing the controller from continually seeking a level when the signal falls below the control threshold.

Installation and Integration

Two 10 kΩ unbalanced phono jack inputs accept a nominal input level of 10 dBV. Two 200 Ω unbalanced phono jack outputs deliver a specified output level of 10 dBV. These stereo phono connections make the signal path direct: connect the variable source to the inputs, connect the outputs to the downstream sound system, and establish the operating gain using the INPUT OVERLOAD indicator.

The FP-ALC2 requires ground-referenced 24 Vdc power at 80 mA. The recommended power supply is not included; the listed options are the PS-24AS for the USA and PS-24AX for international use. Overall dimensions are 1.20 inches high, 3.25 inches wide, and 5.75 inches long, equivalent to 3.05 by 8.26 by 14.61 cm. Its RDL FLAT-PAK format provides a compact enclosure for system integration.

Performance Highlights

Excluding AGC action, frequency response is specified from 20 Hz to 20 kHz within ±0.5 dB. Listed THD+N is less than 0.15%, noise is less than -90 dB below −10 dBV, and headroom is greater than 18 dB. The gate threshold is specified at 40 dBV from 20 Hz to 3 kHz.

The automatic processing combines a greater-than-20 dB level control range with timing that adjusts itself to the incoming program. The INPUT OVERLOAD indicator supplies a clear reference during initial gain setup. Together, these characteristics allow the unit to regulate variable stereo sources while retaining a simple installation procedure.

What Makes It Different

The defining feature of the FP-ALC2 is the way it combines split-band AGC, adaptive timing, gated operation, and single-control setup. Split-band processing is used for audio transparency, while self-adjusting attack and release times eliminate the need for separate timing adjustments. The gate prevents unwanted level seeking, and the overload indicator gives the installer a specific reference for setting maximum usable gain.

This combination targets a precise problem rather than adding unrelated controls: stereo source material that changes level as selections or sources change. The result is an automatic level-control stage with phono-jack connectivity and a compact FLAT-PAK form factor.

Final Assessment

For foreground or background audio systems fed by variable stereo sources, the RDL FP-ALC2 offers automatic level regulation through split-band AGC and gated control. Its two-input, two-output phono configuration, 20 Hz to 20 kHz response, self-adjusting timing, and one-control setup provide a focused solution for maintaining consistent program levels. The external 24 Vdc power supply must be selected separately.