Pass Labs HPA-1 Headphone Amp

In stock

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.

It 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 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 the 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.

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.


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(Size: 4.9 MB)
Pass Labs Amplifiers and Preamplifiers

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

5.0 / 5.0
5 Reviews
5 Stars
4 Stars
3 Stars
2 Stars
1 Star
The last Headphone amp I may ever buy.
The HPA-1 serves two purposes for me. It is a headphone amplifier for my Hifiman HE-1000 headphones and the pre-amp in that same system to two bi-wired speakers. I have input 1 sourcing a very high quality DAC for my streamed, my Disc sourced, and input 2 sourcing my moving coil preamp.
The HPA-1 is a single ended device. I was going to use balanced monoblocks with it and I am now more disappointed that it took me close to 2 years from my initial demo to purchase. My advice is to grab this piece and bi amp or bury larger amps if you must - THE HPA-1 is THAT GOOD for my pre-amp and for my headphone amp. I have and still do own several tube headphone amps. None of the 5 very high quality midrange tube amps can match the sound of the headphone amp in the HPA-1 and though I have a very simple pre-amp, it replaced Nelson’s old Bride of Zen which I built and tweaked over 15+ years. The Bride is retired. Long live the Pass. If I had a “con” it would be having to get Drew to sell me a balanced to 1/4” phone plug. Not a bad price to pay for the last headphone amp I may ever own.
Nestled between some Schiit
The office hifi.
May 8, 2019
8 months ago
Pure Bliss!
No regrets on this purchase. The HPA-1 produces musical sound that's pure bliss. Your favorite works come to life like never before. The older I get the more I appreciate simplicity and that is delivered from controls to circuit design. Bedrock headphone amplification and preamp performance I'll be able to enjoy with a variety of equipment for decades to come! A true value in reference grade hardware, bravo!
February 24, 2019
An excellent preamp as well as headphone amp. It drives my Linn Klout amp and Thiel speakers with more authority and bass control than my Linn Kimax Kontrol preamp ever did in my main system. I matched this with the Focal Utopia headphones and it is absolutely phenomenal. The headphone system is: Klimax LP-12 > Urika > HPA-1 > Focal Utopia
January 26, 2018
Love at first sound
One hour in 1st impression Jacintha's Moon River/The Songs of Johnny Mercer/Dsf most noticeably the immense soundstage, air, and transparency. Jazz At The Pawnshop3/In a Mellow Tone/Dsf details in focus across the wide stage. Neil Young/I'm Glad I Found You/Storytone/Flac vocals so rich, piano so true to life. JRiver/LightspeedUSB/PSAudioDsd/AudioQuestWater/PassHPA-1/AudezeLCD-X with stock power cord. Gorgeous, lush, detailed, expansive sound. Looking forward to the Pre-Amp. Thanks to Drew here at Moon for making the PASS HPA-1 available. This PASS makes it's prowess evident immediately, fulfills it's reference status and will stay with me for life. 5 Stars
October 7, 2017
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!
April 2, 2016
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