Possibly The Best: The 627


Disclaimer: I received a loaner sample of the 627 directly from Portaphile.


My encounter with the Portaphile 627 started with many emails with Cesar, the man behind Portaphile. It didn’t take long for me to understand that Cesar only had one goal in mind and that is to produce the best sounding portable headphone amplifier there is.

A three channel design based on the popular OPA627 op-amps, combined with three BUF634, one for each channel oops, sorry TWO BUF634s for each channels for a total of SIX buffers in a single ended configuration. That’s crazy, considering the powerful Ibasso PB-2 amplifier only has one buffer per channel, for a total of four buffers in balanced mode. Combined with a Jung Multiloop topology, this amp should have it all: both high quality sound as well as power output. For the record, this amp powers the Hifiman HE-6 so effortlessly at only 11 o’clock at high gain. Insane power levels.

When the 627 arrived, I tried it with a few stuff that happens to be lying around in the store, and I was so surprised in hearing the once unlistenable Sony XBA-4 IEM (I called it the IEM with the boombox tuning in the UE900 review) being transformed into a such musical sounding in ear. The Portaphile has this way of smoothing out the treble (not cutting off or rolling off the treble), and filling in the recessed mids of the XBA-4 very nicely. It doesn’t boost the bass and I’m glad it doesn’t since the XBA-4 already comes with plenty of bass. The other headphone was the Sony SA3000 which is the mid-line model from the famous SA1000-3000-5000 model. Like the XBA-4, though not to such extremes, the SA3000 was also weak in midrange body and a bit harsh on the treble. And once again the 627 does its magic, making the SA3000 even more enjoyable than when I paired it with the ALO National (which is one of the best SA3000 pairing I’ve heard).

Though I compared the 627 to some other amps like the ALO National and Matrix Portable, it was the comparison with Ray Samuel’s SR-71A that really got me excited about the 627. I’ve long regarded the SR-71A as one of the best single ended portable amps and still is today, and once I’ve heard how the 627 fares with the SR-71A, I realized that it’s time to bring out all the other big amps to compare it with the 627.

Let’s start with the SR-71A.


627 vs RSA SR-71A

The first thing that stands out is that the 627 has a much bigger soundstage which was mind blowing to me. I knew that the 627 has a big soundstage from the first time I’ve listened to it, but I didn’t thought that the difference is going to be this dramatic since the 71A has always been a respectable performer there.

Transparency is better on the 627, especially on the bass region where the SR71A though has a much better low end body, is significantly muddier on the lows. Midrange and treble is a knock out with the 627. Had it not for the powerful bass impact of the SR71A which the 627 really don’t hold a chance to, it would’ve been a total knock out!


627 vs ALO Rx Mk3B

The Rx line up has always been a spacious sounding amp but again the 627 exceeds it. Not only that but the soundstage depth on the Mk3B is relatively flat while the 627 is more three dimensional and is very natural. Detail retrieval and transparency is also superior on the 627. The midrange is smoother and more natural on the 627. The Mk3B is still a great amp even if I’m only using its single ended circuitry, but the 627 is overall the better amp if you’re talking about refinement, resolution and soundstage.

Bass impact is softer on the 627 but with better detail and transparency. This is the sort of bass that I enjoy for Blues and Jazz while faster paced genres like Rock is better on the Mk3B’s more powerful bass impact. The 627 is not a bass light amp or a bottom light amp, it’s just that the relaxed bass is always a part of the OPA627’s character. It’s extremely special in the mids though, very vacuum tube like in that regards.



627 vs Apex Glacier

I just received the ultra slim Glacier and decides to throw it in this comparison.

The sound quality of the Glacier is very solid and definitely among the best sounding portable amps out there. Single ended, and talking purely on sound quality and ignoring power output (though the Glacier is actually quite powerful), I would immediately rank it as better than the Rx Mk3B’s sound quality (ignoring the balanced features on the Mk3B). The Glacier is very spacious and the detail retrieval is amazing, and the closest to the 627 among all the other amps I compared here. The sound is forward and lively, similar to how the Continental and RX Mk3B are which is quite a contrast from the mellower 627. However when I listen to the sound as a whole, the 627 is far more natural sounding and closer to a big desktop amp. Coherence from top to bottom is top notch with the 627, soundstage is very natural (I’ve said it for a few times now, this is among the best aspects of the 627).


627 vs ALO Continental

The ALO Continental is the only amp I find that rivals the 627 in terms of sound quality. On my first impression, the 627 is superior: wider soundstage, transparency and detail retrieval, refinement, and bass detail. However the Continental also posseses a few strengths of its own that the 627 doesn’t have: the sound is very clean and crystal clean on the Continental, whereas the 627 is quite grainy. Soundstage though narrower than the 627, has a much better depth on the Continental. Overall I do prefer the soundstage on the 627 as it sounds more natural. Vocals are smoother and mellower on the 627, and I know people who digs mellow sounding tube would prefer that sort of a vocals. I, however, like the more forward, crisper vocals of the Continental. It gives me a closer, uncolored vocals which I like better than the more relaxed vocals on the 627. On bass, I enjoy the punchy bass on the Continental better, but low bass presence is much better felt on the 627.

At the end, it comes down to individual’s preference and music choice. I feel that overall the 627 is the more refined, the more upscale amp. However the pace is a little too relaxed for me, a little lacking PRaT. The Continental does the toe-tapping factor better for me, faster pace, more upfront sound, it falls in line better with my preference, but everytime I go back to the 627 I can’t help but feeling how narrow the soundstage on the Continental feels.



Headphone pairings report on the next page…

Possibly The Best: The 627
5 (100%) 1 vote



  • Reply November 29, 2013

    Luke Ma

    how does this amp compare to desktop amps? is it hopelessly outclassed or can it still play?

    • Reply November 29, 2013


      It’s better than many of the cheap desktops.

      • Reply November 29, 2013

        Luke Ma

        so, can it top the crack and the torpedo, or is that too much

        • Reply November 30, 2013


          Depends on the headphone.

          The Crack is very good for the 300 ohm Senns. The portaphile however drives orthos better than the Crack.

  • Reply December 14, 2014

    Chris Vanaman

    Incredible review. Is it fair to say this 627x is a great match with the Beyer T90?
    I’ve narrowed my choices to 2 amps- 627x and Pure II. I just don’t know nor do I have access to test. 🙁
    Thanks for great review, Mike.

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