Pathos InPol Ear headphone amplifier

Pathos and its innovative InPol amplifier circuit has been around for some time – in fact, the Inseguitore Pompa Lineare circuit was patented by Pathos back when the company was founded in 1994 – but its use has mainly been in integrated amplifiers and power amplifiers for the traditional two-channel loudspeaker world. The InPol Ear represents the first time this unique hybrid circuit crosses over into the headphone world – and the results are outstanding!

The term Inseguitore Pompa Lineare translates to ‘Linear Pump Follower’, and the amplifier uses a triode valve to amplify the input signal voltage, and a discrete fully-balanced Class A solid-state follower circuit designed to deliver high current and unity voltage gain to the loudspeakers. Effectively, it means the performance of that input signal and the valve driving it entirely defines the output characteristics of the solid-state amplifier powering the loudspeakers or, in the case of the InPol Ear, headphones. In theory, this should increase the efficiency of a Class A amplifier while also delivering power with optimally low output impedance. A recent innovation by Pathos is the ‘double InPol’ circuit, which is pretty much self-descriptive, and balanced operation throughout is handy for both input and output for any headphone amplifier.

In essence, Pathos has built an amplifier designed for loudspeakers in headphone-sized form. This means the InPol Ear has some extremely impressive specifications, like the ability to deliver up to 10W into a 32Ω headphone load. Put another way, if you could attach a headband to a pair of bricks, the InPol Ear would get a tune out of them. Whether in balanced or single-ended output, the amplifier is simply not going to be phased by any headphone load in existence. On paper at least, this is extremely impressive.

The rest of the circuit design is no less significant. That volume control, for example, is actually a digital volume controller, a Burr-Brown PGA3210, to give far greater precision over channel accuracy and volume setting (it has a range of 180 half-decibel steps). The base of the front of the InPol Ear forms the basic controls, as well as a large red LED volume display, a ¼” jack and two four-pin XLRs for balanced operation. There are four single-ended, and one XLR line inputs, as well as a XLR and single-ended stereo output for those wanting to use the InPol Ear as a preamplifier. I would suggest this last option is relatively limited in reality, because its function as a headphone amplifier (with optional DAC) is paramount, and its secondary function is almost legacy by comparison.

Alongside clever circuitry, Pathos is known for its extremely elegant industrial design, and the InPol Ear is no exception. Italian companies – be it audio brands, car marques, watch-makers, furniture designers, or practically anything else – build their products with style, and Pathos more than lives up to the reputation. The company has an innovative way of dealing with the necessity of heatsinks, by making them the company logo; the name is written along the sides of the amplifier in a stylish, almost Art Deco font. The front and top plates are finished in one of four finishes (three solid colours, one tree-related). At the top of the amplifier are two exposed EH 6922 double-triodes, recessed and shock-mounted in a trio of aluminium plates, and the large volume control is similarly recessed into the front of the InPol EAR. This not only looks great, but is stylistically reminiscent of Pathos designs both current and classic, and the InPol Ear is very much part of a family in look, and sound.

Our version came fitted with the optional Hi-DAC EVO digital circuit. DAC is a relatively simple way of describing this, because usually when one thinks of a ‘DAC board’ added to an amplifier, one thinks of a simple, single USB input or similar. This, instead, is a fully functioning, app-controlled, wired or wireless Ethernet streaming device complete with regular S/PDIF and USB functions. It’s built around the popular ESS Sabre 9018K2M DAC chip, so it is capable of 32bit, 384kHz resolution in PCM, and up to DSD128 through DoP connectivity over USB. The Ethernet streaming facility is driven by the InPol Ear app for Android or iOS devices, however, this is more designed for local play from a network attached storage device. Pulling in tunes from internet radio or some kind of online streaming service is limited to sending it from your iDevice to the InPol Ear via AirPlay. The same does not apply to Android, and there is no Bluetooth protocol.

Sonically, the two underlying themes to the InPol Ear are ‘authority’ and ‘integrity’. The ‘authority’ part comes from that seemingly endless ability to drive more or less anything in the headphone realm (aside from electrostatics of course). There is an effortless sense of power reserves, and freedom from strain that makes the headphones just get on with the job. It’s like cruising in a car with a big V8 engine; there’s so much power and torque to be had, there’s a sense of untroubled calm emanating from every pore. You know that if the going gets tougher, those reserves are there to call upon, and in musical terms, this means the InPol Ear not only ticks the ‘drive everything’ box, but has enough energy in reserve that if you move from breathy singer-songwriter to The Full Monty (or in this case, The Full Mahler – the final movement of Solti’s version of the Eighth Symphony on Decca), nothing gets flustered or troubled.

What I don’t want to overstate here, however, is that the InPol Ear is merely a big lever, for heavy lifting of difficult headphone loads. Or that the amplifier never shifts out of first gear and always sounds a little like there is more to give. It’s more that the sense of having so much in reserve gives the listener a powerful sense of confidence in their music and their replay system. In fact, a lot of my listening took place through the AudioQuest NightOwl Carbon headphones, and even a pair of Sennheiser HD25 II. The contrasts between the two – the mellow tones of the AQ headphone and the hyper-analytical nature of the designed for news-gathering Sennheisers – were demonstrated perfectly through the InPol EAR, but both also gave a sense of being controlled by a benign guiding hand, not in a character-altering way, more in the sense of ‘you can do this’ encouragement to show what both are capable of. The reason I single out these two is the convergence was most marked here: the NightOwls showed those upper frequencies are not rolled off, but designed for lengthy listening sessions, while the HD25 II proved they had more than detail retrieval, and showed that dynamic range is important, too. This applied irrespective of music played – even ‘Lucky’ by Kat Edmonson [Way Down Low, Spinnerette] showed that convergence and this is not a tough track to play.

This leads to that second big InPol Ear theme, integrity. The InPol Ear doesn’t impose its own stamp on the music. It’s characterless, but in a good way. Nothing is out of place here, no sense of emphasis on one aspect of the frequency response, or one aspect of the sonic performance at the expense of others. It works from a quiet background, delivers fine dynamics, great vocal articulation, terrific detail, excellent soundstaging with good solidity of instruments within that stage, and an accurate frequency response. The InPol Ear lends itself to more up-scale headphones because it works at their level, but shows what it can do by dragging more down-to-earth headphones up a notch or two. And as to the simplistic notion that ‘valves = warmth’, this shows that to be a lie. This is not a ‘warm’ (or, for that matter, ‘cool’) sounding headphone amp. It is just a great sounding headphone amp.

Finally… the DAC section. I’d suggest the DAC in the InPol Ear should be a mandatory recommendation as it works exceptionally well, and matches the performance of the rest of the amplifier. It’s aimed more at sheer detail retrieval, and that works well with the overall InPol Ear performance. If I am being picky, I’d prefer more of an on-board streaming solution, so that aspects like Internet radio, TIDAL, and maybe even Roon were functions of the InPol Ear with the built in DAC, but for the most part, I suspect the InPol Ear will sit next to a laptop, and both the Ethernet streaming option and app control are more of a nice add-on than a useful function of the device. Judging by my own use, I used the Ethernet connection to evaluate the Ethernet connection, and listened through USB.

The Pathos InPol Ear is a delight to use. It makes good headphones sound great and makes great headphones sound fantastic. It does this without adding or subtracting to the music played. It merely does the music justice, whatever the music, and comes highly recommended as a result.

TECHNICAL SPECIFICATIONS

• Type: Pure Class A hybrid headphone amplifier with optional DAC
• Analogue inputs: 1× balanced XLR line, 4× single-ended RCA line
• Optional Digital inputs: 1× USB port type B, 1× S/PDIF coaxial, 1× S/PDIF optical, 1× Ethernet RJ45, 2× USB port type A
• Outputs: 1× Pre out stereo line RCA (pre-output phase can be selected), 1× Pre out stereo line Balanced XLR, 1× 6.3mm headphone jack, 2× 4-pin XLR balanced headphone connectors
• Output impedance: 0.9Ω (XLR), 0.45Ω (single-ended)
• Output power: 3W (balanced), 10W (single-ended) at 32Ω, 1.9W (balanced), 6.4W (single-ended) at 50Ω, 800mW (balanced), 2.7W (single-ended) at 120Ω, 320mW (balanced), 1W (single-ended) at 300Ω, 160mW (balanced), 533mW (single-ended) at 600Ω
• THD: 0.1% at 11W
• Signal/Noise ratio: >100dB
• Finish: red, black, white, walnut
• Dimensions (H×W×D): 18 × 28 × 37cm
• Weight: 12.5kg
• Price: £5,395 as tested (£3,449 without Hi-DAC EVO converter)

Manufactured by: Pathos Acoustics

URL: www.pathosacoustics.com

Distributed in the UK by:
UK Distribution Ltd

URL: www.ukd.co.uk

Tel: +44(0)1425 460760

Back to reviews