Headphones continue to be popular but you really need a good quality headphone amplifier to make the most of them. Paul Rigby reviews the Quad PA-One
Headphones remain a popular part of the hi-fi chain. While the headphones themselves are, of course, critical, they need to be teamed with an external headphone amplifier if the headphones are to show their true colours. Headphone amplifiers built into an integrated amplifier or other, more lifestyle, unit are fine to a point, save space and may be convenient in terms of portability but, in sonic terms, they will be inherently crippled.
Quad’s answer to the issue is the PA-One, weighing a hefty 7.5kg square and spanning 180mm x 284.5mm x 163.5mm. This is a meaty, bulldog of an amp that offers an attractive matt finish that gives it that Special Ops/Call of Duty/SAS crashing through embassy windows-look.
There’s a host of input options including balanced, RCA, coaxial, optical and USB (1.1 and 2.0). There are two 6.3mm headphone sockets on the front plus source selection buttons, volume knob and balance control slider underneath this control. I had an immediate issue with this control. Not that it exists but it’s implementation because, if you move it left or right, there’s no feedback indicator to tell you where the natural balanced centre lies. You have to guess which is not good enough.
Output impedance ranges from 32 Ohms to 300 Ohms while a two-position impedance mode adds extra gain when required.
The amplifier features valve amplification namely: two 6SL7 valves, two 6SN7s, and a single EZ81.
Finally, the PA-One also includes a USB DAC running up to 24bit/192kHz.
Spinning my turntable, I began with Bruce Brubaker’s solo piano piece via his Glass Piano LP and the Philip Glass composition, Mad Rush. This piece, in its early stages, lives in the higher realms of the keyboard and frequency band. This is a good test for brightness and stridency. What the Quad gave me was heading in that direction. While the upper mids could hardly be termed as truly bright, they certainly verged on the strident. At the very least, both midrange and treble were finely etched. A couple of minutes into this piece, the piano comes alive with a dynamic, powerful and grand crescendo which involved both higher and lower frequencies. Again, the upper mids and treble exhibited that well lit, almost strident tone while the lower frequencies were strong and powerful. The inherent effect of the upper mids did tend to polish and etch the bass too and, although the lower frequencies didn’t sound particular relaxed or rich in tone, this part of the sonic spectrum did receive a measure of punch and slam to each lower frequency key.
I then moved onto harder rock from 1971 and the Electric Light Orchestra with First Movement. Again, during the introductory Spanish guitar sequence, the Quad exhibited its well lit upper midrange as the higher frequency strings had a finely etched sound that showed danger, at high volumes, of possible listening fatigue. The gamut of lower frequency strings, the very bassy cellos, where lifted up to the ear and shown plenty of detail, though. There was a meaty texture as each bow attacked each set of cello strings and a spotlight was also shone on the low frequency mix, digging a range of fascinating detail from this area.
I tried CD and the Nightingales’ Mind Over Matter album and the track, For Goodness Sake which offers dirty, distorted Iggy Pop-like rock. The Quad did well to keep up with the multi-layered nature of the music, providing excellent instrumental separation and a sense of ease as the textured vocals purposefully clashed with the instrumentation. The Quad did well to sort out the musical mess.
I wanted to see if the Quad’s personality was dependant upon the headphones used to do the testing so I changed the headphones from the HD800s to the HD650s but the well lit midrange effects largely remained and were, if anything rather enhanced to the detriment of the Quad. I then moved further down budget and picked up a pair of B&W P3s (£170). The P3s do have a slightly excessive bass presentation that I find rather too warm in normal, day to day, use. Matched with the Quad headphone amp, though, these ‘phones proved a perfect match. The well lit midrange of the Quad lifted the bass-heavy P3s, adding more life and pizazz and giving the phones an added clarity while honing the midrange detail.
Turning to the digital section of the headphone amp, I plugged in my Astell & Kern AK120 and played Dire Straits’ Money for Nothing at 24bit/96kHz. The upper mids were well defined but a touch less obvious here. Playback was clear, crisp, full of air and space. Although Sting’s backing vocal was rather strident, Mark Knopfler’s lead vocal was lively and musical. Percussion was a little too polished for its own good, although it remained punchy and forceful while guitar was detailed and incisive.
This is a beautifully built and well presented headphone amplifier that is priced competitively and features plenty of features. It’s sound quality is rather skewed towards the etched upper midrange and treble which does tend to dominate but if you like the more clinical approach to sound quality, then the Quad should be worthy of a demo.
QUAD PA-ONE HEADPHONE AMPLIFIER
Tel: 01480 452561
Good: instrumental separation, incisive, spacious mids
Bad: clinical upper mids, balance control has no natural centre
Avid Acutus turntable
SME IV arm
Koetsu Black cartridge
Icon PS3 phono amp
Aesthetix Calypso Preamp
Leema Essentials CD player
Sennheiser HD800 headphones
Sennheiser HD650 headphones
Bowers & Wilkins P3 headphones
Astell & Kern AK120
Phillip Farano31st July 2017 at 10:28 pm
I have not found anywhere on the internet, including the mfg., or by any reviewer, what tubes are supposed to be in V1 & V2 (of course mirrored in V# & V4
Paul Rigby1st August 2017 at 9:53 am
I’ve asked Quad, Phillip – if and when they reply, I’ll pass on the info.
Paul Rigby7th August 2017 at 12:17 pm
Hi Phillip. The full complement of valves used in the Quad PA-One is as follows: 2 x 6SL7 ; 2 x 6SN7 & 1 x EZ81.
William Hawkins30th March 2020 at 12:47 pm
have you had a chance to hear the revised Pa1+? A new chip, reduction in valves. I wonder if it has improved on the slight stridency you didn’t like.
Paul Rigby30th March 2020 at 1:15 pm
Good question and no, I haven’t William. Not yet but thanks for the nudge on this. I’ll ask although I do have a mighty review queue here so I’m not sure if/when I can find space! 🙂