High-quality headphone amplifier. Sounds great with various models of high-impedance and low-impedance headphones. Works well as a preamplifier (when using a 6.3mm - RCA adapter). To ensure the best sound quality, careful selection of electronic components was made. 

Components used:

ALPS volume control; resistors: PRP, Susumu, KOA, Vishay, Yageo; capacitors: United Chemi-Con, Kemet, Panasonic, Yageo; transistors ON Semiconductor, headphone jack 6.3mm Neutrik, relays Takamisawa (Fujitsu), operational amplifiers Texas Instruments (Burr-Brown), gold-plated RCA connectors. The amplifier has been tested and works well with the following headphones:

Audio Technica ATH-AD1000, Sennheiser HD590, HD600, HD650, HD660S, HD800, Beyerdynamic DT770, DT990, AKG K271 MKII, AKG K701, HiFiMAN Ananda, Massdrop x HIFIMAN HE4XX, Audeze LCD-2 Classic, LCD-XC Carbon, LCD-X, Denon AH-D9200, Dan Clark Audio AEON RT, Meze 109 Pro, Sony MDR-R10.

Technical specifications:

Input voltage: 12-24V

Power supply (included): Input: 100-240V ~ 50/60Hz 0.8A; Output: 12V (2A)

Input impedance 20kOhm

Output power 0.3W (32 Ohm).

Frequency range 15 - 80000 Hz (+/- 1 dB).

THD 0.005%.