ST-502 Monitor System (Preliminary)

€ 1200

The ARREL Audio ST-502 MONITOR is an advanced monitor system for studioapplications. Its main characteristics are:


1. Mixer input: Electronically Balanced. Impedance 10 Kohm, Input Level +4 dBu, Max Input level +30 dBu, DB 25 connector.

2. DAC Input: Electronically Balanced. Impedance 10 Kohm, Level +4 dBu, Max +30 dBu, XLR connector.

3. AUX Input (CD/DVD player): Unbalanced, Impedance 47 Kohm, Input Level [ -17 dBu , -2 dBu] , Input Gain control on the front panel (AUX), Pin Jack RCA on the back panel + Jack 3.5 mm on the front panel. The use of the 3.5 mm Jack on the front panel excludes the Pin Jack RCA on the back panel. The CD/DVD/ (AUX) input is amplified and balanced balanced and the output is available on the back panel (TRS Jack). The output is always active and do not depend on the selected input.

INPUT SELECTION: 3 momentary push buttons with electronic interlock (high quality audio relays).


MONO: Push button (LED) relays based

LEVEL: Precision potentiometer with large knob. Motorized potentiometer if requested together with the remote control.

MUTE L: Push button (LED)

MUTE R: Push button (LED)

DIM: Push button (LED). Attenuation from 6dB to the infinity. DIM control is actuated by the TALK push button.

OUTPUTS: 3 Outputs selected by momentary push buttons (electronic interlock)(high quality audio relays) Electronic balancing. Low output impedance External load > 600 ohm. Out level +4 dbu. Max Out level +28 dBu.

Frequency response (-1 dB) 2/200.000 Hz. Total Harmonic Distorsion + Noise THDN 0.001 %

In the ST-502, non used outputs are automatically shortened to avoid crosstalk.

DB 25 connector on the back panel.

HEADPHONE OUTPUT: Impedance > di 16 ohm. Jack TRS on the fron panel. The headphone Jack insertion deactivate the 3 outputs (the selection remains memorized)

TALK: Condenser electret Microphone on gossle-neck base and XLR connector on the front panel. Gain control ( 20 dB range) on the front panel. Mic selection by the TALK push button (LED) (High quality audio relays). XLR connector on the back panel. The TALK push button activates the DIM control.


The remote control requires the installation of the motorized potentiometer. The remote control is connected to the ST-502 unit by using a DB25 standard cable (no audio signal on the connections). The controls on the ST-502 unit are replicated on the remote control.


Input selector

Output selector

DIM Push button

TALK push button

MONO push button

UP/DOWN output volume control Motorized pot.

CASE: RACK 19” x 1U POWER SUPPLY : 220 V 50 Hz 30 W

Power Supply Linear Regulator (Balanced C-Core Transformer)
Operating Voltage 220V 50 Hz / 110V 60 Hz switchable version
Power Consumption 20 W
Microphone Inputs
Microphone Gain 20 dB
Audio input
Audio Output Electronically Balanced for talk, control room monitor, Studio Monitor,
Remote control
Front Panel Controls
Front Panel Input Connectors
Rear Panel Input Connectors
Rear Panel Output Connectors
Bandwidth 5 - 200.000 Hz -1dB, perfect square wave up to 20 KHz
Distortion + Noise <0.003% ( typical 0.001 %).
AC mains IEC C13 16 A connector, AC mains cord with IEC Schuko 16A.
Construction 19" rack mount metal box
Dimensions 19"" 1 Rack Unit
Weight 1.5 kg.

    ST-502 Key-Technologies


    Large Bandwidth (LB) means a very fast transient response able to represent the original sound with the maximum temporal resolution. LB is required to improve the perception of a “real sound” and to represent the details of the original sound.

    Large bandwidth plus very low total harmonic distortion means a perfect square wave reproduction.

    Ultra Low Noise (ULN) active and passive components and ULN design techniques. This requirement is especially important when the audio bandwidth is large as in the case of ARREL Audio products.

    Very High Dynamic Range (VHDR) means that the saturation probability of the output stages is extremely low. This is obtained by using special rail to rail circuits and by increasing the power supply voltage of the analog circuits.

    Electromechanical tolerance means that electromechanical components are doubled in every situation in which maximum reliability it is important due to a frequent use (switches, push buttons, potentiometers).

    Through Hole technology means the maximum reliability in terms of thermal and mechanical stresses especially for connectors and electromechanical components.