Pass Labs HPA-1 Headphone Amplifier

The Pass Labs HPA-1 is a Class A headphone amp that was designed to amplify headphones with impedances of 15 ohms to 600 ohms.    The HPA-1 delivers full-range dynamics and can drive any headphones. It's designed as a Class-A power amp, with a low-noise, shielded toroidal power transformer and discrete low-noise regulated power supply for the audio circuits. Low-feedback, wide-bandwidth J-Fet input, and Class A-biased MOSFET output stages offer superior audio. It easily drives headphones from 15 to 600 ohms and boasts a rotary knob volume control, plus input and preamp output jacks. Its sturdy brushed aluminum casework adds to its appeal.   SpecificationsGain (dB) - 8 dBFrequency Response 10 Hz-100k - 1dBOutput Power into 20 ohms - 3500 mWTHD + Noise - <0.005 at 1V outOut Power into 300 ohms - 200 mWInput Impedance - 50k ohmOutput Impedance - <2 ohmsPower Consumption (Watts) - 23Unit Dimension (W x D x H) (In.). -11 x 13.5 x 4Unit Weight (LBS) - 14   Main Features Works with headphones with impedances of 15 ohms to 600 ohms. Designed as a power amplifier rather than a typical headphone amplifier to be able to drive low-impedance planar headphones. Low feedback wide bandwidth discreet design. Class A direct coupled Mosfet output stage. Custom low noise Toroidal power transformer with a Faraday shield. Discreet regulated power supply for audio circuits.