Pathos Acoustics Kratos and InPol MkII Integrated Amplifiers Compared
REFERENCE AUDIO – WITHAM ESSEX
BOB’s Review Series - No 85 – PATHOS ACOUSTICS KRATOS AND INPOL MK2 AMPLIFIERS
INTRODUCTION
Pathos Acoustics sound like they should hale from Greece, but they are in fact based in Vicenza in Italy and celebrated their 30th anniversary last year. Their current line up of amplifiers covers 18 models including DACs, integrated amps, preamps, power amps and even a 200 W monobloc power amps that retails £46,000 a pair. They also make a massive £52,000 integrated amp that weighs a whopping 140kg and measures 500mm wide and nearly 900mm deep. There are also three headphone amplifiers in their lineup.
Pathos Acoustics is well known and well regarded across the industry for their innovative and patented ‘InPol’ amplifier design philosophy which was conceived to completely avoid any back-feedback in the power stages. Much more on this subject can be found on their website at www.pathosacoustics.it and it makes interesting reading. I think a little description of both amplifiers is warranted here as this might swing a potential customer to prefer one over the other if the different way they sound is not as critical as the way they will be used.
The Kratos - is a Class A/B amplifier heavily biased in Class A outputting 200W into an 8ohm load and 350W into 4ohms. The front panel of the Kratos and the InPol MkII are identical with a large central remote controllable volume control with digital volume readout and two small buttons to the right which select power on/off into standby and source. The volume knob is not of the rotary type, it’s one of those twist and return to zero types. There is a wooden surround to the volume control panel and Pathos offer the option of padouk wood black ash finish. The Kratos has five inputs on RCA and two on XLR, it has twin pairs of speaker outlets and pre-out on both RCA and XLR with a small switch to disconnect the preamplifier stage. The main power on/off is via a small toggle switch also on the rear panel. It also has a front panel headphone output with its own rotary volume control. It also has two vacant bays that can accept an optional extra DAC board at £845. The Kratos has two TungSol 12 AX7 valves in its preamplifier stage, both on view on the top panel. It measures 430mm x 530mm x 195mm (WDH) and weighs 35Kg.
The InPol MkII – is a pure Class A amplifier outputting 45W into an 8ohm load, they say it produces more into 4ohms but don’t specify by how much, I am guessing at around 75W. It has four inputs on RCA and two on XLR. It has DAC capability with rear panel inputs already provided for two USB, one optical and one RCA Coax input but it will need an internal DAC board to be installed as an £795 optional extra to enable these inputs. It has pre-out on XLR only and has twin pairs of speaker outlets for bi-wiring. There is no headphone output on the InPol MkII. It has two TungSol 12 AX7 tubes and two 12 U7W tubes in its preamp stage, again on display on the top panel. The InPol MkII measures 430mm x 530mm x 195mm (WDH) and weighs 38Kg.
Both amplifiers have remote on/off rear connections and come with handheld remote controls. And both amplifiers retail in the UK at £10,995 before DAC options are added.
CONNECTIONS
The review was carried out over several days in one of our listening rooms and the system comprised the brand-new Marantz SACD 10 player (£9,5000) connected with Jorma XLRs to each Pathos amp which in turn were driving the Estelon Aura speakers (£19,500) which are a 4ohm load with a minimum recommended amplifier power of 30W. Towards the end of the review I did swap out the Estelon for a pair of Martin Logan ESL-X electrostatics which are around a quarter of the price but perhaps a more likely price match for the Pathos amplifiers. The Martin Logans present a 6ohm load and at 91dB are a little more sensitive than the Estelon Aura, they are also rated for amps with power output as low as 20W, so they are better suited to the Class A InPol MkII. Their twin 8” bass drivers help to support the electrostatic panel deliver deeper bass and of course each speaker requires a mains connection to charge the electrostatic panel.
In the image attached the Kratos is on the top shelf and the InPol MkII sits below it.
LISTENING
I should confess to being a Class A convert having a 50W Class A power amp in my home system but I’m also aware of just how good Class A/B amplifiers are these days having owned and tested a variety over the years, so I guess I’m reasonably well qualified to compare these two amps from Pathos Acoustics. The Marantz SACD 10 is a formidable CD player (review coming soon) and was used virtually exclusively as a source component for this review, I did try some streamed music but concentrated on the SACD player as a source, bringing in my own collection for this review. I listened to SACDs of Alan Parsons ‘Eye In The Sky’, Pink Floyds ‘Wish You Were Here and Dark Side Of The Moon’. I also played the UHQCD of Dire Straits ‘Brothers in Arms’ and the XRCD of The Eagles ‘Hell Freezes Over’ to ensure I had the very best source driving both Pathos amplifiers. Other SACDs and CDs were also played for a comprehensive review.
Before listening in depth to the two amplifiers that are the subject of this review, I set up the Pathos T.T. Integrated amp that retails in the Anniversary Edition at £7,195. The standard T.T. Remote Reference retails at £6,795 but it excludes the XLR inputs of the Anniversary edition. This is also a pure Class A amplifier with output of just 35W into an 8ohm load and if you get to see one in the flesh you may think it looks quite small in comparison to many of todays integrated amplifiers but try and lift it and you will appreciate that that this is a serious bit of kit. It weighs in at 43kg, that 95lbs in old money. And when I say it runs hot, it runs seriously hot so it’s not an amplifier to hide away in a cupboard, not that you would want to, just look how gorgeous it is. With just 35W to play with and with a short listening window for the T.T. Anniversary I wired it up to a pair of Dali Epikore 7 floor standers that were to hand and which at 88dB sensitivity and a recommended minimum power amplifier rating of 40W was probably not the ideal match, but the T.T. Anniversary was more than up to the task. Using an Innuos Pulsar streamer and Ideon Ayazi DAC and Reclocker the sound was warm and inviting, driving them with enthusiasm but perhaps not the full dynamic control I’m sure the T.T. can deliver into more suitable speakers. I wasn’t surprised by this result and felt a change was in order, so I swapped the Dali’s for a pair of Sonus Faber Olimpica Nova 1 standmounts which are a 4ohm load and rated for amplifiers at 35W upwards. The Sonus Faber proved a better match to the T.T. Anniversary both in terms of driveability and price, but I felt that neither speaker was really giving the T.T. Anniversary room to breathe. I hope to come back to this amplifier when more time allows for a more in-depth review and when more suitable partnering speakers are available. But it did give me a good flavour of what to expect from Pathos in terms of performance and build quality when setting up the Kratos and InPol MkII amps.
Getting back to the subjects of this review and when setting up the Kratos and InPol Mk2 integrated amps my first thought was why would any sensible manufacturer of audio amplifiers bring to market two identically priced yet technically diverse amplifiers? I’m not sure I have an answer to that, but I guess Pathos have done their marketing research and can see a customer base for both in their portfolio. But what an opportunity this represents to a reviewer or potential owner to be able to directly compare Class A with Class B from the same manufacturer and at the same price point with their favourite speakers.
The Class A/B Kratos – The Estelon Aura speakers used for this review are rated at 4ohm and 90dB efficiency and the Kratos outputs a hefty 350W into a 4ohm load, so it is more than capable of driving the speakers to high volumes with full dynamics, and it certainly did so. The Kratos is a slightly dryer sounding amplifier than I would have expected from one with a valve front end and if you didn’t know it had a couple of 12AX7 valves you would probably just assume it to be a fully solid-state amplifier from how it sounds. Using the Marantz SACD 10 and playing a variety of SACDs and red-book CDs revealed an amplifier fully capable of resolving all the detail on the recording. It can play as loud as you want without clipping but beware, that power output is prestigious, your ears will give up before the amplifier does. Mark Knopfler’s voice on ‘The Mans Too Strong’ from the Brothers In Arms SACD 20th Anniversary edition was clear, expressive and articulate and his guitar clashes were as dynamic as you would ever expect or need. Vocals and guitars were working in harmony. The Brothers In Arms track was as soulful and moving as ever. The UDSACD disc of Alan Parsons ‘Eye In The Sky’ (Mobile Fidelity Sound Labs) is a great album and I listened to it from start to finish, it sounded just great with expressive soundstage. This amplifier sits perfectly well with its peers at this price point and will provide enough power and detail to provide an owner with a lifetime of enjoyable and rewarding use.
Back when I was a teenager and still not old enough to drive a car, I passed my motorbike test on a Honda CB72 250cc bike and one evening I was in the Rising Sun pub in Walthamstow (sadly no longer a pub) and I purchased my very first real 12” album from a guy at the bar and proudly rode home with it stuffed inside my leather jacket. That would have been around 1970. We don’t have a great selection of CDs at Reference Audio but oddly we do have that one and I just had to play it. That 12” vinyl was Paranoid by Black Sabbath. On went the title track and suddenly I was 16 again. For the first time in years, I played the whole album from start to finish and savoured every moment. The Kratos has just the right amount of drive and headroom to deliver this album with the full head banging joy of life that was abundant way back then. On went ‘Iron Man’ and that opening drum beat by Bill Ward was stunning in its dynamic influence and when the guitars kicked in, I was a youth all over again.
The Pure Class A InPol MkII – One of the reasons for choosing the Estelon Aura speakers for this review is their 90dB efficiency and minimum recommended amplifier power of 30W and as Class A Watts always seem to be more powerful than the rating suggests the InPol MkII rating of 45W would seem to be reasonably well suited although even more efficient speakers would be worth considering. As I mentioned earlier, I’m more sensitised toward Class A amps these days and when I disconnected the Kratos and plumbed in the InPol MkII it was like coming home. It was immediately more involving with more depth and warmth and for me it was just so much easier to connect to emotionally. It just sounded so right in every way. I played all the same SACDs and CDs over again and was never disappointed and never wanted to go back to the Kratos. You of course might have differing criteria than me when listening to music and I can fully understand some preferring the greater headroom and dynamic control offered by the Kratos over the InPol MkII especially if you are into rock, but for me there was clear winner.
I listened to the SACD of Eleanor McEvoy’s ‘Yola’ and again listened from start to finish, the last track ‘Something So Wonderful’ summed up how this album sounded via the InPol MkII, it was completely involving and just as she sings in this track, ‘something so pure’. I did have to up the volume a bit for the InPol MkII over the Kratos to cater for the very big difference in wattage, but not as much as I had expected, those pure Class A watts again. This 45W Class A amplifier will play sufficiently loud on most of today’s speakers that are likely to end up being partnered with the InPol MkII. Older speaker designs will need more careful pairing with the InPol MkII because they tend to be less efficient than more modern designs.
I have a DVD A (anyone remember them?) of King Crimson’s ‘In The Court Of The Crimson King’ but of course the SACD 10 wouldn’t play it, not many players will these days. Luckily, I also have a CD version so I played ‘Epitaph’ and ‘Moonchild’ and with Greg Lake on bass guitar and lead vocals this album couldn’t have sounded better, lots of emotion, keeping my attention to the detail revealed by this remarkable amplifier.
CONCLUSION
I recently read an article about a sea lion that has perfect rhythm. It was able to nod its head to music and hold and keep a beat better and more precisely timed than most humans can. Something that researchers had always thought could only be done with creatures that have some sort of speech capability, i.e. mostly just humans. Then I read an article about chimpanzees that can tap out a beat and rhythm on trees to communicate across large distances. Depending where in Africa the Chimps live depends on their musical preferences and how they beat out a rhythm to communicate across vast distances. Chimpanzees are our closest evolutionary cousins and clearly share some of our desire towards pace and rhythm. But more interestingly researchers have found that our ability may have existed long before we were humans to a time when the last ancestors of humans and chimps are thought to have lived, that was around 7 million years ago. Today being able to discern beat and rhythm is what sets us apart and is why music is so important to our everyday lives.
Back to present time and the differences between these two similarly priced and specified amplifiers are not subtle. Both can hold a beat and rhythm and if you like to play your music loud and long and have relatively insensitive speakers, then the Class A/B Kratos is for you. If, however, you listen at more sensible volumes, have more efficient speakers and like to hear all the fine detail and emotion in the music then the Class A InPol MkII is the one you will choose. Both run hot and if that is a problem for you in terms of the environment or where you will be locating the amplifier then you may need to look elsewhere. I imagine that the InPol MkII will use more energy as Class A is less efficient than Class A/B and this may also influence which one you choose. I wouldn’t recommend putting either inside a cabinet no matter how well-ventilated it is, but why would you, both amplifiers need to be seen. But the InPol MkII just has more verve.
Swapping out the Estelon for the Martin Logan ESL-X was interesting, and I do confess to having a liking to panel speakers having owned several pairs over the years. Both amps worked well with these speakers but again, for me, it was the InPol MkII that suited my preferences and these more allowing those panels to do what they do best, give amazing clarity and soundstage with a wider and more defined stereo image. At just £5495 they are a bargain.
Both these Pathos amplifiers deliver outstanding value for money and deliver the musical appeal that makes for long and rewarding listening sessions. They can evoke emotion and connection to the music, and that my friend is “Pathos”.
May 2025
Bob – Team Reference Audio