Pathos Inpol Ear Reference Headphone Amplifier Review and Discussion God that name, why didn't they just call it "Pathos Inpol Headphone Amplifier"? There are basically no reviews of this amp on the internet, and due to a kind local headphone enthusiast I met on USauduiomart, I was able to borrow it. He has now joined SBAF and his username is @tinker . thank you @tinker ! So I figure I need to write something about the amp. GEAR Pi2AES -> AES-> Yggdrasail A2/og -> XLR out -> Pathos Inpol Ear Reference -> Various modded Audeze headphones mostly modded LCD-4 but also my modded HE6SEv1. I don’t have any electrodynamics to use, and wouldn’t know what to say except "eeewwww electrodynamics" (in a whiny voice) even if I did. In other words, I don’t really like electrodynamics no matter what the amp is (for the most part), so it’s hard for me to evaluate an amp with transducers I not only don’t know well, but don't really like. So keep that in mind. I suspect that given the design of this amp, it is a good implementation for orthos so it doesn’t make much difference. Upscale Audio recommended this amp to me when I was looking at the Felix Envy (mostly with lust) as a powerful amp for orthos. DESIGN This is a big amp with a completely unique design unlike any headphone amplifier you’ve ever seen. Huge heatsinks on the sides are raised above the bottom of the amp and the front face is forward from the base, giving it a kind of floating look while still looking quite muscular. A LOT of work went into the design of this amp. I believe a lot of work went into the acoustic design as well. But the question we have to ask is: how much? TLDR; This is a great sounding amp, it’s got great tone, leaning more on the SS side than the tube/euphonic side but it still has tube attributes. It’s powerful, clean sounding while mantaining natural warmth, resolving and has decent dynamics. It’s a bit flat sounding though in terms of dimension and dynamics and realism and just lacks that X factor that makes music come alive and transition from "I’m listening to headphones" to "I’m listening to music". Yes, it is a great amp, but it is not an amazing amp. And at the price tag of over $5000 it needs to be a GREAT amp. It is not. I can’t help but wonder how much of that price tag is going to the fancy design. I think sound wise, it is worth about $2000 or maybe less. Design wise, it commands much more because it’s’ so fancy. AESTHETICS AND FUNCTIONALITY I think a picture is worth more than me describing the amp. Here are some images. This is the lacquered black version, which is highly reflective in photographs. I could get out my studio lights and avoid this, but I'm not going to. But in person, you don't see these refections you just see a shiny black surface. The heatsinks annoyingly spell out "Pathos" and I wonder how much that cost to have made instead of regular heatsinks. One of the most unique features is something you’ll probabliy love and hate at the same time. Instead of a regular potentiometer that you turn up and down for volume, and which is counterclockwise at lower volumes and clockwise at higher volumes, this has what would on the surface appear to be a digital volume control, the large circle, which is the only thing on the front plate of the amp is the volume control. You turn it to the right and numbers pop up on the bottom screen telling you what volume level you’re at. So it only turns from 12 oclock to about 1:30 and vice versa, and turning it this much makes the volume level displayed in numbers go up or down. It’s not actually a digital volume control though. I can’t find the description of this volume control, but Pathos website says it uses "2 x Burr Brown PGA2310 (180 steps 0,5dB)" I've been told this is "digitally switched resistor analog attenuators". The point I guess is that it’s analog, but has tiny steps to ensure perfect channel matching at every volume level and much less crosstalk so you can set it to get the exact right volume. It’s fun to use, but also annoying because you can’t just turn the volume up or down quickly to get to the right level, you have to hold the knob and wait. I would prefer a regular high quality potentiometer. And to that effect, I would prefer them take out the guts of this amp and just put it in a regular enclosure and charge less. The amp screams "I have money" and I just hate that aesthetic. I prefer industrial designs like the og Cavallli Liquid Gold. SOUND Pathos says this on their website about the design for whatever it’s worth: "Inpol devices have a special sonic personality obtainable only by means of this particular circuit design - fully balanced in Class A using a single solid state component in follower configuration, with high current gain and with voltage gain together. The valve amplifier amplifies the input signal voltage and InPol supplies the current to drive the loudspeakers without any further amplification. In this way the signal is entrusted to the valves and becomes a true copy of the original, with all the quality, purity and harmonic content of the original. This technology allows an increase in the theoretical output in pure Class A of between 25% and 50% together with a low output impedance which is fundamental for the damping factor, and further improved by the double InPol." I don’t hear anything particularly special though. It has more authority, grip and control with hard to drive headphones like the LCD-4 and HE6 than my Liquid Glass (also a tube hybrid), but with more sensitive headphones like the LCD-4z, the Liquid Glass has a bigger soundstage, and a much much more nuanced sound that is full of gobs of detail, holographic imaging, incredible realism, gorgeous liquid leading edges to notes and better dynamics. So the Pathos is more powerful, but sounds quite a bit worse than the Liquid Glass. It’s sound is smooth compared to most solid state amps, but maintains a pretty solid state sound where you get more square edges and more flattened dynamics and a lack of that delicate resolution that tubes bring. You can still hear tubes in the mix because it has a smoother sound than most solid state amps, but it’s minimal. I often found myself kind of bored listening to it. It doesn’t have a very big soundstage which surprises me when looking at the amp. I don’t know about "wrap around" or "blobs" because I don’t really listen to soundstage much. I do think a lot of people would like this sound though, those who prefer a solid state sound but might appreciate a bit of the benefits of tubes. Or those who want a goddy medal of honor in their rack instead of an amp. I’m being serious, this design will appeal to a lot of people, who want to spend a lot and have that represented in the aesthetics. Whereas an amp like an Eddie Current or Cavalli amp don’t scream money and visitors would not think "money" when looking at them. The amp takes 6922/ECC88 tubes exclusively. I tried a variety of tubes in the amp from the very lush Philips tubes to Siemens and Tesla and they didn’t change the sound of the amp that much, contributing to the idea that the sound of the amp comes more from its' solid state topology than the tubes. Comparison to my SOHA1 with the modded HE6SEv1 NOTE: My SOHA1 is no ordinary SOHA. I sent it to @dBel84 to figure out why it sounds so good and this is what he had to say about how it sounds so good while being such a simple and cheap (at the time) design. "Pavel [the builder of the amp @Fallenangel here on SBAF and on Head-fi] used the JISBOS from Ti Kan as a unity gain output stage - each little buffer probably costs more than the entire rest of the amp - it uses now extinct Toshiba Jfet input transistors ( Nelson Pass LOVES these little Toshibas ) = 2SK170 / 2SJ74 with some of my favorite power BJTs as output devices - MJE243/253. Today the little JFETs cost $75 a pair although when he built it, they likely only cost a few dollars. BUT , this combo is highly desirable and makes for an EXCELLENT output buffer." I compared my SOHA1 to a First Watt Aleph J and the Aleph J just barely sounded better driving the HE6. The SOHA1 beat an F7 driving the HE6 by quite a bit. The Pathos amp is at nearly max volume at listening level while my SOHA1 is at about 9:30. Not an indicator of power, but with these amps i think it is, I can keep raising the volume on my SOHA and it doesn’t sweat. They have pretty similar tonal balance My SOHA1 has a bit more euphony, liquid leading edges, and depth. It has a more tube sound than the Pathos, which is flatter in presentation My SOHA1 just sounds more real, while the Pathos sounds more boring to me My SOHA1 doesn't’ loose anything vs the Pathos with the HE6 while beating it in many ways. Pathos vs RAAL PDT-1a with modded LCD-4 The PDT-1a is better in every way. Unless you hate the sound of tubes. It’s got a bigger sound, better more realistic tone and timbre, better grip and control of the drivers, more resolution, a more delicate approach to fine details with more beautiful attacks and leading edges of notes. Maybe they have equal bass control. The Pathos just sounds kind of boring in comparison. But again, its not bad, it does a good job of driving the LCD-4 it’s just not special like the PDT-1a is. FINAL THOUGHTS Can I recommend this amp? No, not at over $5000. Not at all. But it’s not shit at all either. It’s not a cold sterile solid state amp and it’s not warmpoo. It’s well tuned. It just lacks that last bit of finesse and realism that the best amps have. It’s a bit flat and lifeless. So even if it were priced more accurately at about $2000, I would not want this amp, it’s just not my thing. But I think a lot of people would like it for the reasons mentioned above- the combination of tubes and solid state but veering on the solid state side. There aren’t many amps that have that particular balance. Big, statement Italian design, great but not amazing sound.