Pass Labs HPA-1c

The revised supply is described as providing superior signal-to-noise ratio and sonics, while Pass Labs says distortion is lower than before. The review does not provide detailed listening observations about separation, low-level detail, air, or perceived resolution.

The review says the sound compensates for the unit's deliberately bare-bones control set, but does not characterize its tonal balance. There is no specific evidence on warmth, neutrality, timbre, treble character, or long-session musicality.

The unchanged Class A MOSFET circuit supplies 3.5W into 20 ohms, and the reviewer considers its roughly 3W-at-32-ohm capability sufficient even for difficult loads such as HiFiMAN Susvara and RAAL Magna. That suggests meaningful current delivery for challenging low-impedance headphones, though there is little direct description of transient attack or macro-dynamic impact.

Wayne Coburn states that the new power supply lowers the noise floor and distortion, with the revision explicitly intended to improve signal-to-noise performance. No listening report addresses hiss with sensitive IEMs or residual hum, so its behavior with the most sensitive loads remains unconfirmed.

With 3.5W into 20 ohms, sub-2-ohm output impedance, and reviewer confidence for Susvara-class loads, the HPA-1c appears well suited to difficult low-impedance planar headphones. Its modest 8dB gain and 200mW rating into 300 ohms warrant some caution for unusually voltage-hungry high-impedance headphones, and the review provides no sensitive-IEM pairing evidence.

The review identifies a new power-supply implementation and notes the compact, substantial 23W Class A operating design, but offers little direct assessment of chassis execution, controls, connectors, or long-term reliability. Finish is available in black or silver, though cosmetic options alone say little about durability.

The HPA-1c has two single-ended inputs, a switched line output that can serve as a minimalist preamplifier, and a simple front-panel headphone/speaker mode switch. It lacks balanced inputs, a built-in DAC, remote control, and other modern convenience features; the reviewer specifically calls the preamp utility bare-bones by contemporary standards.

At approximately $3,995 to $4,045, this is a premium-purpose headphone amplifier with a particularly minimalist feature set. The review does not compare it with price rivals or make a clear judgment on whether its sound and build justify the asking price.