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Product Description


Introducing the new Rx portable earphone amplifier from ALO audio. Made in Portland, Oregon, U.S.A.

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.


The RX is a revelation for its price and an instant winner for me with just about every IEM I tried. Pot balance was neigh on perfect with zero noise floors on sensitive BA such as the W4 and the dynamic IE800. Volume control was steady and never maxed out or felt too vague. The RX tonally is neutral with a hint of warmth and plenty of top end air, extension and sparkle without ever sounding tizzy, bright or too hot.”  Read More

- Marcus D @

"I really love the Rx, combining a great build, loveable sound and a clear purpose, it does exactly what it says on the tin, they don't exaggerate anything on the product page and I have a lot of respect because of that. If you want an amp to truly bring forward the performance of your earphones, then why are you going to look further than this? For that reason we will give this our Great Value award!" Read More


- Sonny Trigg @

Additional Information
  • Electroless Nickel Plated - Limited Edition
  • Black Anodized Finish
  • Brown Finish
  • Brown (Lotoo Edition) +dB for pairing with PAW 5000 portable hifi audio player
  • high quality conductive plastic element type potentiometer for extended life, high resolution and high reliability over carbon element type pots.
  • Single-Ended 3.5mm stereo input and 3.5mm stereo output. 
  • Rechargeable via micro USB.
  • Ultra-Low Noise Floor 
  • Optimized for IEMs
  • Made in Portland, Oregon USA.

Special edition Brown Cryo-Fi cryo treated Rx portable earphone amplifier from ALO audio.

Pushing the limits of HIFi fidelity we have implemented the proprietary ALO Cryo-Fi cryogenic treatment process for the entire Rx amplifier system. The Cryo-Fi process achieves a full liquid immersion cryogenic treatment process. We use a highly specialized computer controlled cryogenic processor to process all of our hifi products and wire. We use a total immersion technique that fully suspends the Rx in liquid nitrogen (LN2) for a proscribed time at -186 degrees Celsius. The Rx is held at this temperature for the prescribed time and then using precise computer controlled operations the temperature is safely brought back up to ambient temperature to complete the process.

The process of cryogenic treatment aids in the aligning of the internal stresses of the metal structures, this process allows the electrons to flow less inhibited. The stresses that have built up in the manufacturing, assembly process / heat are reduced and the parts are cryo annealed. In addition, the grain structure and arrangement of carbon in the metal is more uniform that before cryogenic treatment. The net results are a amp with more focus, better dimensionality, and a warmer presentation, more relaxed sound and low notes that have extended decay. For that extra edge in sonic performance we apply the ALO Cryo-fi process to the award winning Rx IEM amp!



Available in Nickel, Black Anodized or Brown Finish

Size and Weight

Compact Size of New Rx Earphone Amplifier

Inputs / Outputs

3.5mm Stereo Input, 3.5mm Stereo Output, Rechargeable via USB

Warranty 1 Year Limited Warranty
Tech Specs

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.

Gain: Approximately -14.6 dB.

In The Box

New Rx - Ships with USB Cable, 3 Amp Straps and 110-240 Wall Charger

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