Balanced Version= With 2.5mm Balanced out Interface and still have 3.5mm interface Standard Version= Only have 3.5mm interface WARNING! F1 is designed to drive high-impedance earphones, essentially set to what is high-gain mode on other amps. This leads to distortion (when using 3.5mm se out) or extremely high output level (when using 2.5mm balanced output). Solution is in post #9. https://www.head-fi.org/threads/walnut-f1.858439/#post-13674030 Tip: If you have 2.5mm earphones, you can plug the output of your DAP or phone into "Power out" socket. This will utilise balanced output buffers only, bypassing opamp and volume control altogether. See post #17 for details. https://head-fi.org/threads/walnut-f1.858439/page-2#post-13675934 1. Interface: 3.5MM or 2.5 interface 2. Output power:300mW 3. Operational Amplifier Chips Model: OPA2134 4. SNR: 90DB 6. Lithium battery capacity: 1500MAH 7. Charging Interface: Standard MICRO USB. Package: 1 X Headphone Amplifier(earphone not include) 1 X Charging Cable 1 X AUX Cable 2 X Silicone straps Walnut F1 amp size is small, 80 * 50 * 20mm than a bank card is slightly smaller, but the small head also has great wisdom, this section of the sound of the amp should be said that the bile is more foot, simply is the sound more sweet The Plus after the amp; Can feel out the sound field is significantly large, opener is the original BB of the OPA2134. Sound characteristics in general are warm and delicate type, strong driving force, "bile". Low-frequency quality and quantity. At the same time 2.5mm version with a balanced output, balanced output has been applied to professional recording field, balanced output is characterized by high degree of separation, the thrust is about twice the power output. operational amatement OPA2134, OPA2134 is designed for audio and designed for the op amp, sound mellow, rounded, neutral warm, bile is very strong, is known as the most electronic tube audio amplifier. Feeling like the upgraded version of 5532, all aspects have greatly improved, good resolution, music taste better, there is bile, the sound is relatively thick and a bit rigid, comprehensive quality is very good. Especially for music performance. The amp can be replaced by the op amp. Direct plug design. Is now the mainstream design, different op amp to bring a different tone. Almost completely using the machine's power supply circuit, up to 24V (+12 V gnd -12V) of the pressure, easy to control the various types of op amp on the market, the strength of the launch of the loud field. While supporting the side of the charge while listening to music. Power supply part of the selection is 24v 1A power supply, ripple very small (using the commonly used three-terminal regulator 78M12 79M12, under normal circumstances no noise at the end), the filter capacitor is Ina vr series and gold fw series of high-quality capacitors The Imported high current full-shielded inductors. (16 ohm-400 ohm), and due to the high supply voltage, long-term use of the shell will be a slight signs of fever (not more than 30% of the use of a class of current amplification and op amp voltage amplification, degree). The use of 3.7V high-capacity lithium battery-powered, boost to 24v maximum current 1A, battery capacity 1500mah, life 4 to 5 hours or so. When charging the use of Andrews can be a common charging line. Do not use when charging. Charging time about 2 and a half hours. (When charging red light, stop charging green light) Output coupling DC blocking capacitor using Ina SILMICII 220uF ELNA silk fiber purple palm brown audio electrolytic capacitors, the strength of the extraordinary enough to be among the ranks of the world's advanced audio capacitors. Using the OFC oxygen-free copper feet, very low distortion (third harmonic distortion-120dB), very small tangential loss, natural silk fiber media, high-quality sound, play silk soft and natural, enhanced resistance to acoustic oscillation design, Increase the sense of low-frequency thick, reduce the high-pass part of the peak value of the Peak and the middle part of the rough sound quality.