TechPowerUp published a review on the HIFIMAN EF400 Desktop R2R DAC and Headphone Amplifier
A quote from the article:
HIFIMAN returns to the desktop DAC/amplifier market with its EF400 source that uses the company's self-developed R2R HIMALAYA DAC paired with a truly balanced topology and a Class AB amplification circuit. It offers extensive headphones and line outputs off just USB input and puts out a unique sound signature which plays very well with HIFIMAN's own planar magnetic headphones.HIFIMAN EF400 Desktop R2R DAC and Headphone Amplifier Review