Absolute Volume

USB DACs and Bluetooth DACs receive digital audio from the source device and perform D/A (Digital-to-Analog) conversion.

When adjusting the volume on a PC or smartphone (the source device), the most convenient way to control it is by lowering the original audio volume before transmitting it to the USB DAC or Bluetooth DAC receiver.

Examples of volume control methods include:

• Volume slider in audio players

• Volume slider in YouTube playback screen

• Volume slider in Foobar2000

In these methods, the original audio remains intact only when the volume is the maximum, but lowering the volume reduces the digital audio's bit resolution.

When adjusting the volume through these methods, the audio signal is scaled down, which can reduce sound quality.

The absolute volume adjustment method preserves the source audio's bit resolution when transmitting digital audio to a USB DAC or Bluetooth DAC.

The Absolute Volume adjustment method is supported by all major operating systems, including Windows, macOS, iOS, and Android.

In the Absolute Volume method, the audio is always transmitted with its original amplitude, regardless of the volume setting. The volume value adjusted on the PC or smartphone is transmitted to the USB DAC or Bluetooth DAC, and the receiver reflects the volume level it receives from the source device.

However, Android OS has a bug where the USB Audio Class does not support Absolute Volume. Therefore, when connecting an Android smartphone to a USB DAC, Absolute Volume is not applied.