Portable desktop-friendly headphone amplifier / DAC / preamp combo 
Allows audio playback through USB, S/PDIF or TOSLINK sources 
It uses the latest generation AKM 4490 chip, which features 32-bit processing and supports sample rates up to 384kHz PCM or 256x DSD. 
Two power operation modes – LOW and HIGH. 
LOW power mode is from USB connector #1, which provides bus power along with data, allowing the m900 to operate from a single connection to your computer. 
HIGH power mode is available by connecting the included 2A USB DC power supply to the USB connector #2, which provides additional power for harder to drive headphones. 
Mono Mode 
Left minus Right 
Channel Balance adjust 
Monitoring Modes (stereo, L&R swapped, left in both channels, right in both channels, left channel only, right channel only) 
7 segment LED display displays level and setup menu information  
Large rotary encoder for volume control and setup menu navigation  
Made in Lyons, CO USA  
5-year transferable Warranty 
 
Dimensions (LxDxH): 102 x 133 x 46mm 
 
Front Connectors: 
2 x Headphone Output (¼” Jack Connector) 
 
Rear Connectors: 
2 x Line Output (RCA Phono Jack) 
1 x S/PDIF Input (PCA Phono Jack) 
1 x TOSLINK Input (Optical) 
1 x micro USB-B for high power input 
1 x micro USB-B for data/signal/bus power input