Quad PA-One+ Headphone Amplifier Review

Sex Education.

It’s a show I’ve been watching on Netflix and it got me thinking.

It’s something everybody gets in middle school – or earlier – depending on what latitude and longitude home is, because it’s an essential part of how one learns to navigate the strange waters of being an adult.

I think Quad education is important for anyone becoming a serious lover of music playback, because learning about the contribution the company made to high-fidelity is an essential part of learning to navigate the strange waters of being an audiophile.

Quad education because they’re an icon of high-fidelity that started their run in the ’50s, ’60s and ‘70s with company founder Peter Walker’s electrostatic speaker and amplification designs that few audio engineers would discount as a reference standard (I touched on the the Quad ESL 57 in my PA-One+ preview). You can’t really tell the story of British hi-fi (or hi-fi in general) without including Walker’s groundbreaking work, and you can’t really talk about Quad without touching on their early designs because they are what made the company what it is today (it was originally known as the Acoustical Manufacturing Company, but it turned out ‘Quad’ which stands for ‘QUality Amplifier Domestic’ was easier to remember).

Quad made huge technical strides in the industry and were ahead of the curve when it came to alternative speaker designs and stable amplification, and as with all things that are both high in quality and reliable in operation, it became a brand to emulate.

Build, construction and connectivity

That lineage, that heritage, brings us to the newly designated Quad PA-One+. Full disclosure, I never heard the original PA-One, so I have no reference to compare the previous iteration to this upgraded model.

Solidly built and classically styled.

To my eyes it is classic Quad design and build from the ’60s, and is as iconic-looking a modern headphone amp as there ever was with design cues lifted from the likes of the legendary Quad II mono bloc (an amp design I still covet and know that I will own one day just to have heard it as a reference). Large isolation feet anchor the substantial, oversized transformer casing at the rear which compliments a caged crown of 6SL7/6SN7 tubes paired atop its chassis at the front (run in triode configuration implementing cathode feedback), and a large metal-alloy volume attenuator dwarfs the four-pin balanced and quarter-inch unbalanced headphone outputs and input-selection buttons (line input/balanced/single ended, digital input USB/Coaxial/Optical and a toggle switch for Standby Mode and On/Off) on the thick, solid-metal fascia.

Well laid-out and accessible controls.

The rear panel boasts both balanced and RCA analog inputs, along with Coaxial, Optical and USB on the digital side and a set of unbalanced pre-amplifier outputs if you want to drive a stereo power amplifier or a set of mono blocs. There is also another toggle switch here for running the amp in either high or low impedance modes, a mains rocker switch and a detachable AC socket for facilitating aftermarket cords (the amp comes equipped with a standard cord and a USB cable, which I did not use for this review, preferring instead an AudioQuest NRG-10 AC cord and my Final Touch Audio USB cable.

USB in, along with Coaxial, Optical on the digital side.

The PA-One+ utilizes an two-channel ‘audiophile grade’ HyperStream ESS Sabre 9018K2M ‘Reference’ DAC chip capable of both asynchronous and synchronous 32-bit/384kHz PCM and DSD256 decoding. For this review I ran a Roon Nucleus+ into the PA-One+ with 16-bit/44.1kHz (FLAC rips) 24-bit/192kHz, DSD64/128 local-drive downloads and TIDAL and Qobuz streaming files. I did not tube roll the Quad as even though I have acquired (and continue to acquire) ever more tubes, they tend to input/line/phono applications, and I had no varietals of 6SL7/6SN7). I did not use it as a pre-amp either, rather, I focused on it’s headphone amp/DAC abilities. I used a variety of headphones, of varying impedances and sensitivity from the Audeze LCD-2 Classic, Mr. Speakers Aeon Closed, HIFIMAN HE1000se to Quad’s own Planar-Magnetic ERA-1, which had real synergy with the PA-One+ and that I settled on for all my critical-listening and review sessions.


jodet's picture

It's a spectacular headphone amp. Sounds amazing on my HifiMan Arya's. It seems most headphone amps only have one input, this has three digital and two analog, one RCA and one XLR.