The HA-2SE's power amplification circuit for the headphones is Class AB built with integrated circuits (ICs) and discrete transistors. The discrete transistor output stage uses hand-picked and matched parts. The output transistors are biased to operate in their most linear range for the critical small signal, and deliver their full potential when power is required._x000D_
The DAC is one of the most important components for digital audio playback. The ES9028-Q2M DAC chip used in the HA-2SE is the latest flagship mobile DAC developed by ESS Technology. With the ESS patented 32-bit Hyperstream™ DAC architecture and Time Domain Jitter Eliminator, the SABRE32 Reference DAC delivers an unprecedented performance for mobile applications._x000D_
By bypassing the smartphone's built-in DAC and headphone amplification circuit that are often cost-constrained, the HA-2SE turns a smartphone into a high performance digital audio player. The asynchronous USB DAC input of the HA-2SE also works with PC and Mac computers to replace the built-in sound card and support high-resolution audio playback with PCM up to 384 kHz 32-bit and DSD up to 12 MHz (DSD256)._x000D_
There is no DSP (Digital Signal Processor) in the HA-2SE. Volume control is operated by a combination of the DAC chip's internal digital volume control and an analog potentiometer (the familiar volume knob). Bass boost is performed by pure analog audio circuits. By avoiding re-digitizing the audio signal for volume adjustment or bass boost, the HA-2SE provides a clean signal path for the audio._x000D_
The HA-2SE has a 3.5 mm Audio-In port to support portable music players that do not have a USB-compatible digital output. While the HA-2SE is used with one of its USB digital input ports, the 3.5 mm jack acts as Line-Out for the USB DAC._x000D_
For those who like a bit more punch and impact with their music, the HA-2SE offers a Bass Boost function. With Bass Boost off, the HA-2SE delivers a ruler-flat frequency response; with Bass Boost on, the HA-2SE adds force and impact to the sub-bass region without muddling the important mid- to high-frequency bands._x000D_
The HA-2SE offers two gain level settings for optimal headphone matching. The High Gain mode is capable of driving large power-hungry headphones, delivering up to 300 mW into 16-Ohm headphones. The Low Gain mode is intended for sensitive In-Ear Monitor type earphones.