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Pathos Classic One MKIII Integrated Amplifier Review

Doug Schroeder on a pair of the $5,500 Pathos Classic One MKIII: how his fever got higher

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“The Classic One in bridged mode utilizes only the right channel, so that the class-A tube preamp stage is paired with a high current A/AB amp stage.”

The Classic One in bridged mode utilizes only the right channel, so that the class-A tube preamp stage is paired with a high current A/AB amp stage. Thus, only one set of tubes is actually operative in the signal path. I discussed with Gianni in removing the left tube to keep it from unnecessary use. He admitted that he was unsure if it would be wise to do so. We decided to keep the left channel tube in place. Truly, the power and grace of this little number in mono is staggering! I have had tubed pre/amp combinations as well as tube pre/SS amp combos approaching the $10k mark that have not dislodged the Pathi from their favored position in my rig.

I have never been one to attempt “realistic levels” of concerts in my room, so I was not too concerned about over-driving them. From several months of use of these amps, I can say with certainty that the conservative listener, who uses volume judiciously, will never need to worry about using 4-ohm speakers. In bridged mode, such speakers are child’s play to these amps. They have power galore. I rarely need to take the level, which is indicated by red LED’s tastefully residing next to the gold volume and selector knobs on the unit, past 45% of the units’ capacity. Only on some older, very poorly recorded discs, have I used the units at the 60-70 setting out of 100. Even then, there is not the slightest hint of stress. Nor is there the slightest buildup of heat. The Classic One produces negligible heat in my experience. I wouldn’t put it in an entirely closed cabinet, but would have no hesitations putting in on a lower shelf of a rack.

Pathos Classic One MKIII

In fact, like the Siren call of the bridged mode, the amps beg you to turn them up! I find myself wanting to listen louder because the relaxed nature of the presentation. I know my ears will not be assaulted, so I take the volume higher…

“I played guitar ages ago, and remember the feel and sound of the “roundness” of the string as it’s plucked. In bridged mode, that roundness comes through convincingly.”

The effect of bridging the amp moves the soundstage forward and outward. Rather than the singer or instrumentalist seeming to be ten feet away, they seem five, like the distance has been halved. This is especially noticeable on solo instrumentals like the unusual The Silent Life by Jonas Hellborg. His acoustic bass guitar takes on immediacy as one can hear not just strings plucked, but the “roundness” of the strings and the sound as it bounces off the guitar’s soundboard. I played guitar ages ago, and remember the feel and sound of the “roundness” of the string as it’s plucked. In bridged mode, that roundness comes through convincingly.

The bass is powerful, tight, but not digital sounding. I had been using a digital amp and tube preamp prior to the Classic One. One of my fears was that I would lose detail in the bass by moving to a tube hybrid amp. My fears were completely unfounded. I discovered that I preferred the Classic One’s bass.

“On lesser amps, the sound of the air could be considered mechanical, but the Classic One reveals the sound is biological. With good amplification, even breath has a discernable tone.”

Regarding some of my listening sessions, Howard Jones sometimes sings, sometimes softly shrieks. I like listening to the shrieks, when his voice falters and the breath takes over as the note dies. It’s not that I like Howard Jones’ voice that much, it’s that I can hear what the components are doing! From the disc In the Running, on “City Song” the bridged One’s put his voice five feet away, with his head turned slightly to one side, slightly more emphasis on one side of the Mic…you can hear his lungs empty out. On lesser amps, the sound of the air could be considered mechanical, but the Classic One reveals the sound is biological. With good amplification, even breath has a discernable tone.

The word Pathos comes from the Greek language and means “deep emotion.” The supplied Sovtek 6922 tubes have a lovely sound. Gianni indicated that Pathos tried several different tubes, but concluded the Sovteks yielded the best sound-to-value ratio. I tried a pair of Electro-Harmonix 6922’s and found them to be slightly more detailed, but also more clinical. I preferred the stock Sovteks and to date have stuck with them.

Bridging the amps also refines the treble; the decay of cymbals is much more discernable than in stereo operation. The room/setting of the recording is far more palpable. The imaging is stunning. Regarding the phantom image, I am aware that the vocals are not coming from my HT center channel, but it sounds like they are. The Pathos amps are so open, so voluminous sounding that nearly everyone who listens, including seasoned audiophiles, ask if the surround system is on. It never is, but everyone wonders.

How did the remote work on two amps simultaneously? Marvelously! My concern was that I would forever be adjusting one or the other amp. I could see a nightmare develop where if I selected a source, or changed the level, one amp would respond and the other not. But this never developed, partly I believe due to the positioning of the amps. They reside about 1 foot apart, centered on the component shelving – and why not? They are gorgeous and should be the focal point of the system! But this also makes it very easy, even for the dual emitting remote, to capture both units simultaneously. Even when using the remote slightly off-center the amps respond in lockstep. Only when the remote is on extreme angles does one amp lag, and this is usually only one digit. A quick flick of the volume control on just the right angle to affect only one unit restores perfect balance. I couldn’t be happier at the coordinated way the two amps work together. Almost invariably the units operate as if there is a physical link between them.

Pathos has just recently come out with the MkIII, which improves upon the MkII by a transformer upgrade and binding posts encased in plastic to increase protection of the amp.

What makes me laugh with glee about the bridged Classic One’s is that these are the entry level amps from Pathos! These were listed at $2,295 but can be found for less new, IF you can still find them, because of the arrival of the MkIII. I consider the fully balanced, powerful performance of two of them to be a bargain at the price point. Pathos is out to prove the point that stunning components can be made for the masses. They’re doing a good job of it!

CLASSIC ONE MkIII in Bridged Mode

Now let’s get to the fun part of the review, since we’ll focus on the MKIII version which is more engaging in every respect!

The physical and electronic differences are such that it can be tricky to determine whether one is dealing with a MkII or MkIII. I recently sold my MKII units, and the buyer called, asking in a worried voice, “These are the MKII version, aren’t they?” The appearance is so identical between the original model and the MKII, and the manual not upgraded to pronounce the new version, that he thought he might have paid for the updated version but received the original! I assured him that he had the correct units; the most distinguishing feature of the MKII’s I found, for reference, is the slot cut in the bottom of the chassis allowing easy access to the Stereo/Mono switch.

The physical changes are listed in the specifications above. As a user, the following changes are operationally significant:

1. The plastic coated binding posts and circuitry to prevent shorting is crucial. I always had a fear in the back of my mind that one loose cable could spell disaster with the MKII; now I am at ease and do not fear for the life of the amps.

I nearly had a heart attack when I first went to hook up the spades of the MIT cables I was using. The MIT’s with their “I-Conn” system have removable terminations. As a necessity, this system uses a “bolt”, which protrudes from the cable, and the termination screws onto it. The end of the bolt protrudes more than a smidgen from the front vertical face of the spades. Meanwhile, the new posts on the MkIII have a funky protrusion on their back side almost exactly where the bolt on the MIT spades hit! Well, not exactly, but close! The posts of the MIT spades just fit into the gap made by the hollow under-portion of the binding posts on the Pathi. I would have been seriously P.O.’d if they were incompatible, but it went. They shouldn’t scare people like that!

2. The improved volume control which can accept up to +/- 12V audio signal can in some cases be a life saver. At about the same time I experimented with the “Pathi” (plural for Pathos; credit for the term goes to Gary, a dual Classic One user in Hong Kong), two other audiophiles triangulated with me; one lives in Hong Kong, the other in Australia. We’ve got the Pathi world covered (thinly, but covered nevertheless)!

My Australian correspondent, Paul, has had a horrible time with the bridged units. He complained initially of weak sound, thin sound, lack of dynamics, etc. (I thought it was just him! Sorry, Paul! J). It wasn’t just him, but it was component incompatibility in the context of his Ayre CX-7 cdp. The Ayre has a 4.5V output, and the MKII amp accepted only up to 2V input. Ooops! Mismatch! No wonder Paul had horrible sound (He had said the amps were so weak that at 50% of available power he could hear his breathing better than the audio system! ) as the amps were being sent a signal outside of their parameters, resulting in input saturation.

This is the only technical foible I have learned regarding the Classic One MKII in bridged mode. Likely, 999 of 1000 users would never encounter this issue, but it’s good to know so that you can check for potential mismatches between sources and the Pathi. Upon learning this, I immediately had to consult my Rega Saturn manual to gain reassurance; it listed 2V max output. I knew from what Paul had described that my player was well within parameters acceptable to the Pathi, for my unit sounded nothing like he described, but for the obsessive audiophile it’s always good to know the numbers.

In stereo mode, the unit seems unaffected. Paul discussed with me how much he preferred the single unit in stereo mode. That convinced me he really never has heard the Pathi in their true monoblock glory. Gianni has been quick to address this weakness, and the MKIII can accept up to 5V input. Those acquiring MkII units in the secondary market for the express purpose of operating them in mono bock mode should touch base with their source manuals to make sure the output falls within acceptable parameters.

3. Electro-Harmonix 6922 Tubes are now standard in the MkIII. The MkII used Sovtek’s, and with that particular unit I preferred them to the set of Electro Harmonix that I received from Musical Surroundings, Pathos’ U.S. distributor. I anticipated receiving replacement Sovteks, but it had turned out Pathos no longer used them. There had been reliability issues, and the Sovteks were no longer being made.

I can confirm the longevity issue from my own experience. I wasn’t sure if it was due to operating the units in bridged mode, as Gianni told me that it had no effect on tube longevity; but I went through three pairs of tubes in just over twelve months, although this was not that big of a deal, at around $8@ for the Sovteks. The tubes would not die, but would drop in output and dynamics about 15%, enough that when it happened I could clearly hear the mismatch between Left and Right channels. Since my units were in mono mode, I kept rotating a good tube into the proper socket and was able to keep going. Finally, the third tube went and I had to obtain a new matched pair.

The replacement Electro-Harmonix 6922’s were a bit more stiff and cleaner sounding. Conversely, the MkIII carries the Electro-Harmonix brand installed from the Pathos factory, and with the tweaking that has been done to the unit I unequivocally state that I prefer the EH tubes in the MkIII to the Sovteks in the MKII. While not a perfect comparison, it does show that Gianni is matching his tubes to amps exceedingly well. I anticipate that the EH tubes will yield longer use; Pathos switched to the EH’s as tube life was an issue with the Sovtek 6922’s. I vouch for the change, as the MkIII is bolder and cleaner sounding than its precursor, yet retaining the sweet sound for which Pathos is known.

4. Curiously, the biding posts utilized in mono mode seem to have been reversed between the MkII version and the MkIII. This is a perfect example of the necessity of reading manuals even if one thinks they are perfectly acquainted with a product. Had I not studied the connections information of the MkIII, I would likely have put the speakers out of phase. This is not lethal to the MkIII’s, but it would mean diminished performance. In fact, I purposely wired the amps the opposite of the manual to determine if possibly a clerical or printing error had slipped into the manual. No, in fact the amps did sound better with the cabling as indicated. But, the sound even out of phase was good enough that most people would never guess it was mis-wired. That’s a mighty odd compliment for an amp!

5. The new op-amp feeding the upgraded transformer has resulted in a much more lux power scheme. Upgrading from the MkII’s to the MkIII’s nearly doubled my usable power. The wattage has not been upped, but rather I suspect the current has been boosted nicely. Experientially, I now use half the level I did previously with efficient speakers and approximately two thirds as much level on less-efficient speakers. Whereas at times I used to float in the 60-70 range on the front digital readout of the amps, now with the MkIII’s I have not gone beyond 37-45 in the loud listening sessions. Truly, I am barely beginning to tap the reserves of the MkIII’s. An impressive demonstration of the newly improved power is the fact that I often had to push closer to 70 on the readout to drive the Eminent Technology LFT-8B’s. Now, I can settle between 45-50 and still feel plenty of palpability, yea, the same impact experientially as I obtained with the MkII’s.

The entire experience the MkIII’s create is cleaner and more intricate than the already good previous version. Just one example; India Aire sings a song entitled “This Too Shall Pass,” with a chorus as follows:

…but then I hear a whisper that this too shall pass
I hear the angels whisper that this too shall pass
my ancestors whisper that this day will one day be the past
so I walk in faith that this too shall pass

As she sings this, a small chorus of women’s voices ever so gently whisper the words as she sings them. Using the MkII Pathi, I was only able to detect the echo effect and not the distinct whispering. It took the upgraded MkIII to reveal this ever-so-subtle aspect of the song. The additional clarity takes one to the heart of the piece, as the “angels” are whispering in India’s (and our) ears! That revelatory moment came when the Legacy Focus HD’s, speakers of prodigious expression, were paired with a version of the Classic One that was refined enough to extract the most ethereal elements in the music.

The Focus HD’s, capable of astounding power and finesse for a speaker well under $10k, have reinforced my admiration of the Pathi. It seems there is no end to the upside on the performance of these amps. That, of course, is a foolish statement, knowing that all electronics have their boundaries. So far, however, the boundaries keep getting pushed outward for the Pathi to an extent that it may be a while before I run into one of them.

9 Responses to Pathos Classic One MKIII Integrated Amplifier Review

  1. Keith S says:

    I have Magnepan 3.6r’s
    wondering your thoughts on 2 MK111 powering these bridged?

  2. Keith,
    God’s Joy to you,

    Simply, briefly, I think it would sound beautiful. Pay special attention to the source, because if perchance you feel there is not enough high end snap, this can be aided by selection of the source – and cables.

    I have no doubt that you could achieve a glorious sound with the Pathi; as I indicated in my article, I was able to make engaging systems with nearly any combination of speakers and the Pathos amps in bridged mode.

    Douglas Schroeder

  3. Wayne says:

    As I have interest on Pathos amplifiers for my Sonus Faber Olympica Nova 3s, that I just found this review, thankfully.

    I wonder if you have ever compared this bridged classic one mk3s with other Pathos amplifiers, like Inpol2 or TT.

    Here I can get ‘2 new classic-one mk3s’ at around $4k, and ‘used Inpol2’ at around $4.5k from a dealer at distance, I’m restricted to visit for audition them.
    So I need any of opinion / advice on my decision; “2 x classic one mk3” vs “Inpol2” vs “TT”.

  4. Alan says:

    Hi Doug,

    There’s no doubt synergy is everything. I tried the Classic Mk III in my system as an experiment to see what my Pure Audio Project Quintet 15 Voxatives would sound like with fast solid state power. I loved everything about the Mk III, and yes the look was fabulous. Alas it just was a bust in my system. I tried rolling various 6922s and just could not get it to work. Sold the Pathos and am back being all tubes.

    Best regards and stay safe,


  5. Wayne, Alan,
    Christmas Joy to you,

    The PAP Trio15 (can’t speak in regard to the Quintet, as I have not used it) would likely be perceived as somewhat light on the bottom end with the Class One, even in mono mode. It takes a lot of amp to make the twin 15″ open baffles have presence. The use of the PAP-C1 is very helpful in that regard, as the relative output of the horn to the bass can be contoured. In terms of the particular perception of tonality, color, etc. it is going to be quite personal.

    I am in the midst of an amplifier review wherein I am using 2,400 wpc (600×4) with the Trio15 Horn1 and also employing the Legacy Audio XTREME XD Subwoofers, with sensational results. The noise floor of this class D amp is stunningly low, so that the PAP now is quite advanced from the review systems. Older recordings are able to be played at higher levels with no perceived degradation from amp noise. The speakers have extremely deep and sonorous sound field now, and the timbral richness without low end bloat is, frankly, better than tube amps I have used. The review of this amp will be forthcoming in 2021.

    Douglas Schroeder

  6. Stephen DeVincentis says:

    Hello Doug. I am updating my speakers to Spendor D7.2 and am considering getting 2 of the Classic Mk III.Your impressions would be very welcome…..Thank you in advance…..Steve

  7. Steve,
    God’s Joy,

    Have you seen the discussion at Audiogon in regard to the Pathos?

    No one can tell you which would be preferred. Only a direct comparison can tell. For instance, the Krell may drive the speaker better in terms of macrodynamics, but it may be less desirable tonally. Anyone who simply tells you one or the other is “better” holistically without an actual comparison is guessing.

    Douglas Schroeder

  8. Aitor says:

    Hi Doug, how would mk2 pair in monoblock or is it stereo with Klipsch forte 3 or Cornwall? Thanks

  9. Aitor,
    God’s Peace,

    My impression of that combo is that it would be very good. The amp in all versions has such a sweet midrange and inoffensive top end that I believe it would pair quite well with these kind of speakers. I had recommended the Classic One for the Tannoy Glenair Speaker, which is in the same sector of speakers, imo.

    Douglas Schroeder

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