ALO Audio Rx Portable IEM Headphone Amplifier

ALO Audio

Introducing the new Rx portable earphone amplifier from ALO audio.
  • In 2009 Audio Line Out LLC first introduced the Rx portable amplifier. Years later much has changed in the world of portable audio. But our commitment to uncompromised sound remains the same.

    The new Rx is an exciting continuation of our most popular and award winning line of portable amplifiers.  Redesigned and optimized for IEMs.

    The Rx employs a wide band integrated amplifier and push pull power supply.  Improved power filtering provides an extremely quiet supply and ultra low noise floor.  This means you will hear the music and nothing else.  

  • Dynamic 15 Volt Amp Design

    Huge dynamics are the result of our new 15 volt amplifier design.  15 volts being the difference between the positive and the negative supply rails in the amp.  Many other audio amplifiers rely directly on the battery voltage, some as low as 3.3 volts.  While higher voltage does not automatically result in better sound, the loudest undistorted passages are the direct result of the voltage used.  The difference between the loudest undistorted passage and the quietest passage is our target dynamic range.  The new Rx’s 15 volts give it plenty of headroom for the loudest passages to be reproduced wide open and without distortion.  We always want to make this as large as possible when designing an amplifier.  The highly filtered power supply keeps quietest, most subtle passages crystal clear and free of distortion or encumbrances.

    The new Rx's  quiet power supply uses the newest low ESR Aluminum Organic Polymer Capacitors to give it extremely clean peak power performance. The frequency response extends flat from below 10 Hz to above 50Khz.

    Super Low Output Impedance

    The new Rx  has super low output impedance. This allows it to deliver superb audio performance to earphones and more specifically, low impedance In Ear Monitors.

    The theory of low output impedance is straightforward.  As source impedance approaches zero, the ability to drive a varying load impedance improves.  

    Earphones typically have low load impedances and those load impedances change with the audio frequency reproduced.  Multiple drivers in an earphone can create complex impedance loads for amplifiers trying for flat reproduction.  Lowering the output impedance of the amplifier helps to mitigate the effects of changes across the audio frequency.  

    Another advantage of low output impedance is the effect on damping. Damping is the ability of the amplifier to control the drivers, and  without a good damping ratio (via low output impedance),  a diaphragm will tend to ring or 'bounce' a few extra times after it first moves to produce music.  Low source impedance prevents extra movement because it is electronically 'stiff'.  The reduction of the 'bounce' in the diaphragm results in higher fidelity reproduction.

    Broad Frequency Range

    A good audio amplifier will have at least a 20 Khz upper frequency limit. This is also considered the upper limit of audible audio frequency.  As the cut-off frequency of the amp approaches, the amplitude of the signal reproduced at and above this frequency is reduced.  If distortion free music reproduction is your goal, you want the amplifier’s cut-off frequency to extend past this point to reduce coloration.   Moving the cut-off point upward keeps the changes away from the critical audio range.

    The new Rx cut-off frequency is out near 80Khz.  This insures that no effects are present in the desired frequency range.  Our tests show the effects of the cut-off frequency first begin to appear around 50Khz. This is well beyond any audible ability to influence our target audio range.  It keeps your music crystal clear and distortion free during amplification.

    Super Low Distortion

    Keeping distortion to a minimum is critical for a high fidelity amplifier.  Distortion here is the addition of 'stuff' not present in the original presentation.  For example, added  harmonics, bounce or ringing in the earphone, and cross talk of mixed signals are all things to avoid in high fidelity reproduction.

    Good solid state amplifier practice is to hold distortion to below .01%.  Our target at listening levels is to stay well below that number.  The new Rx spec is about .002% distortion.   This goes well below any other amplifier we've produced to date.   While not every amp benefits from lower distortion automatically, the new Rx's low distortion is certainly a strength. 

    Recharge via USB

    Convenience is king when it comes to charging your amplifier.  And looking for your charger instead of listening to your favorite tracks is a drag.

    That is why the new Rx is rechargeable from any normal USB charger. It will automatically vary its charging current to match the charger used.

    The maximum charging rate is set at 900 mA. This allows it to take advantage of any available charger. Charge time will increase with chargers that deliver less current.

    Our charger uses a clever scheme to watch the input voltage from the USB supply or port.  If the input voltage starts to drops, the amp will reduce its current demand. This prevents a potential system shutdown if many devices are charging from a single computer.  It also keeps charging optimized to a safe charging level at all times.   

    Typical charging is less than three hours from the included charger, and similar charging time is achieved from a standard high current port on a laptop.  Older computers or laptops may  produce a longer charge time.

    High Quality USB

    A quality USB cable is important to charging time as well.  A low quality cable can drop the voltage with small wires and poor connections.  This is why we've included the Green Line USB cable with the special edition Nickel plated Rx.  A high quality USB will ensure the most consistent and best results. A black high grade USB charging cable is included with the black Rx amps.

  • Frequency Response (Measured at 1V RMS Output):     

    • 20Hz to 20Khz     +/- 0.05 dB
    • 20Hz to 50Khz   +/- 0.6 dB

    THD+N, (Measured at 1 V RMS Output):

    • Less than 0.002% from 100Hz to 50Khz

    Input Impedance

    • 10K ohm

    Output Impedance

    • Less than 0.5 Ohm
    • IEM optimized variation

    Output power

    • (With an input of 2V RMS the Undistorted output power Into the typical IEM (Which can have an impedance of 5 Ohms) is limited by design to a safe power level of 28 mW.


    • Approximately -14.6 dB.