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Pass Labs HPA-1 Headphone Amp


Pass Labs

Moon Audio

Hot New Products,Drew's Picks,Amplifiers,Preamplifiers,Amps, DACs & Gear,Headphones,Pass Labs,Los Angeles Audio Show 2017,

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Pass Labs HPA-1 is a Class A headphone amp that was designed to amplify headphones with impedances of 15 ohms to 600 ohms.

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.

Pass Labs HPA-1 Review - Feb. 2017 - PartTime Audiophile




Pass Labs' HPA-1 Headphone Amplifier can deliver full-range dynamics across the entire frequency range. The HPA-1 can even drive headphones that present difficult loads in terms of impedance, power consumption or both.

In order to stand out from the crowd, Pass Labs' designers conceptually designed the HPA-1 as a real Class-A power amplifier, not as an accessory offering only incremental performance gains. The HPA-1 cuts no corners in the circuit design and spares no necessary expense in execution.

The foundation of the HPA-1's engineering is a custom, low-noise shielded toroidal power transformer feeding a discreet low noise regulated power supply for the audio circuits. The importance of the power supply is often overlooked and plays a large part in overall performance of the amplifier.

The HPA-1's amplifier circuits are low-feedback, wide-bandwidth discreet designs employing J-Fet input stages and Class A-biased direct-coupled MOSFET output stages.

The HPA-1 easily drives headphones presenting loads from 15 to 600 ohms, particularly excelling on planar headphone designs. The sound is rich and detailed.

The HPA-1 has a single high-quality headphone jack on the front panel, two sets of single-ended analog inputs via RCA jacks on the rear panel, and also a set of switchable "Preamp" line-level output jacks on the rear panel. There are no compromises with the HPA-1 when used as a stereo preamp, and it will compete against contemporary preamplifiers. The rear panel holds the power switch and fuse. Volume control is via a hefty rotary knob connected to an ALPS Potentiometer. The other front-panel controls are three pushbuttons to select inputs or to engage the Preamp output.

The substantial casework is the customary and well-recognized brushed aluminum shared with other Pass Laboratories products.

CNET Review by Steve Guttenberg - Mar. 2016

ToneAudio Review - August 2016

Alpha Audio Review - July 2016

Stereophile Review - July 2016

6Moons Review - February 2017


Have Questions?

Find answers to common questions on our guides.



Additional Info



Output Power into 20 ohms 3500mW
Output Power into 300 ohms 200 mW
Frequency Response 10hz-100k -1dB
Gain 8 dB
THD + Noise < 0.005 at 1V out
Input Impedance 50K Ohm
Output Impedance < 2 ohms
Power Consumption 6 Watts
Dimensions  4.5" H x 11" W x 13" D
Weight 14lbs


AccuracyReview by Macon
I had the opportunity to sit down with HifiMan HE-1000 headphones and the PASS HPA-1 for a good 30 minutes. Listening to Miles Davis's Kind of Blue the Cannonball & Coletran's saxophobes staging was dead on with every note.

Switch to Morphine the sax and bass were just as pin point and lush. I tried to listen to a wide variety of music. I headed to the Ws and found Widespread Panic: simply amazing. I can go on and on but you need to check out Mr. Somasundram's masterpiece for headphones.

Two of my personal favorite demos are Crazy & Killer by Seal. Who knows what a synthesizer is supposed to sound like?

I'll say, if it sounds good then i'm happy. Killer had dynamics that I rarely, if ever think about - with the PASS the quieter passages are still full of detail and when the bass & drums come along, they literally pop out and grab me.

I concluded with Bonnie Raitt - I think i'm in love!
(Posted on 4/1/2016)

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