Enhanced Compatibility: U3 adopts simple RCA input and 6.35mm headphone output, while U3 PRO is upgraded with 3.5mm AUX/stereo RCA input and 3.5mm/6.35mm headphone jack output. The U3 PRO is compatible with more audio sources, including MP3 players, iPods, smartphones, tablets, computers, and CD players etc., and more headphone models as well. Built-in Voltage Boost Circuit: U3 PRO adopting innovative circuit design with built-in voltage boost circuit, the amplifier circuit can work at a higher voltage of ±14V even only powered by DC 5V, and the background noise index is excellent. With wide frequency response extension, excellent transient response, excellent purity and transparency, and good dynamic range.
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