Format-A Twisted Pair Remote Controlled Mixer

The RDL FP-TPX3A is a three-channel, remote-controlled audio mixer built around Format-A twisted-pair inputs. It provides VCA level control for each input pair, a balanced mono output, two unbalanced RCA mono outputs, output-level metering, and audio-presence detector outputs for coordinating connected equipment.

Ideal Use Cases

The FP-TPX3A is suited to installed audio systems that require remote control of multiple Format-A sources. It can be controlled directly by RDL remote controls with two or three channels, using twisted-pair interconnection between the mixer and the remote control.

When only two twisted-pair inputs are needed, the third input is available locally through the detachable terminal block for Pair C. This local input can accommodate a balanced line-level source, including a paging source. The combination supports systems in which distributed program audio and a local paging feed must share the same mixer output.

Why Choose This Model

Each of the three input pairs has its own VCA level control, providing more than 90 dB of attenuation when the corresponding remote-control volume is off. Front-panel gain trim allows the input levels to be matched to active or passive Format-A senders. This gives the installer direct adjustment at the mixer while preserving remote level control during everyday operation.

The output section provides three connections for the mixed signal: one 150-ohm balanced output on a detachable terminal block and two 1-kilohm unbalanced outputs on RCA phono jacks. Nominal output levels are +4 dBu balanced and -10 dBV unbalanced, supporting both balanced line-level equipment and devices with consumer-style RCA inputs.

Installation and Integration

Format-A sources connect through RJ45 inputs, while the local Pair C input uses a detachable terminal block. The balanced output also uses a detachable terminal block, and the two unbalanced outputs use RCA phono jacks. Remote-control communication is carried over twisted pair, and compatible RDL two- or three-channel remote controls connect directly to the mixer.

Power connections include a terminal block and two DC power jacks. The power requirement is 24 Vdc at 120 mA plus the current required by connected Format-A senders. Recommended power supplies, which are not included, are the PS-24AS for the USA and PS-24AX for international applications.

The unit measures 1.42 inches high, 3.25 inches wide, and 8.14 inches long, equivalent to 3.61 by 8.26 by 20.68 cm. Its front-panel controls and indicators provide access to gain matching and operating status after the audio and control connections are in place.

Performance Highlights

Frequency response is specified from 20 Hz to 20 kHz within ±0.25 dB. THD+N is less than 0.05% from 20 Hz to 20 kHz and less than 0.02% at 1 kHz. Noise below a +4 dBu output is less than -100 dB with all channels off, less than -75 dB with any channel on, and less than -70 dB with all channels on.

The FP-TPX3A provides more than 18 dB of headroom above +4 dBu. Common-mode rejection is greater than 80 dB from 50 Hz to 150 Hz. A dual-LED VU meter displays the mixer output level, while a separate audio-present indication reports detector activity.

What Makes It Different

An integrated audio-presence detector operates at a threshold 35 dB below the +4 dBu output level. Its open-collector outputs are intended to enable power amplifiers or system power when audio is present. The release delay can be selected for 10 or 20 minutes, allowing connected equipment to remain enabled through normal pauses before being released. This detector-based control can provide energy savings when used with compatible system-power or amplifier-enabling arrangements.

The ability to combine three remotely controlled inputs, substitute a balanced local input when only two twisted-pair feeds are used, and connect a paging source to that local input distinguishes the FP-TPX3A from a basic fixed-control mixer.

Final Assessment

The FP-TPX3A brings Format-A input connectivity, per-input VCA control, balanced and RCA output options, local-source flexibility, gain matching, output metering, and audio-triggered equipment control into one three-channel mixer. It is a focused choice for an RDL Format-A installation requiring direct compatibility with two- or three-channel RDL remote controls and a selectable detector release delay.