Portable Headphone AmplifierPHA-3

Charging the battery via a computer

The headphone amplifier contains a rechargeable lithium-ion battery, which should be charged before using it for the first time.

  1. Rotate the power/volume knob counterclockwise, until it clicks, to turn off the headphone amplifier.

    The battery charges only when the headphone amplifier is off. Rotate the power/volume knob clockwise to turn on the headphone amplifier. Rotate it more to adjust the volume.

  2. Connect your booted computer to the DC IN 5V port of the headphone amplifier using the micro-USB cable (supplied).

    The POWER/CHG indicator lights up in red while the battery is being charged, and the indicator turns off when charging is completed.

    Charging is completed in about 15 hours.*1

    If the battery is not charged properly, the POWER/CHG indicator will flash in red.

    *1 Time required for empty battery to recharge.

When the battery cannot be charged

  • Check that the headphone amplifier and your computer are firmly connected via the micro-USB cable (supplied).

    Use only the supplied micro-USB cable. Do not charge the battery using any other USB cable.

  • Check that the computer is turned on and not in standby, sleep or hibernation mode.
    If the computer enters standby, sleep, or hibernation mode while the headphone amplifier is connected to the computer, the POWER/CHG indicator turns off and the battery charge will not be completed properly. In this case, change the computer settings and then charge the battery again.
  • Check that the headphone amplifier is directly connected to a computer using the micro-USB cable (supplied). Charging may not be completed properly by an indirect connection, such as via a USB hub.

Battery life*2

Analog connection: Approx. 28 hours*2

Digital (balanced) connection: Approx. 5 hours*2

*2 when using the headphone amplifier at 1 mW + 1 mW output (24 Ω). Time may vary, depending on the immediate environment or conditions of use.


  • The charge will continue for about 10 hours, then the timer function of the charge protection circuit will stop the charging. If you want to continue charging, disconnect and reconnect the micro-USB cable.
  • When the headphone amplifier had not been used for a long time, it may take a while for the POWER/CHG indicator to light up in red. In this case, do not disconnect the micro-USB cable from the headphone amplifier. Wait until the POWER/CHG indicator lights up in red.
  • Charge the battery in an ambient temperature between 5 °C to 35 °C. If you try to charge the battery outside this range, the POWER/CHG indicator may flash in red, but the battery may not be charged.
  • When the battery is full, the POWER/CHG indicator may not light up in red.
  • When storing the headphone amplifier for a long time, avoid a place subject to high temperatures. When storing the headphone amplifier for more than a year, charge the battery every six months to prevent over discharge.