Portaphile 627 MICRO


Headphoneus Supremus
Pros: POWER, solid construction, no detectable channel imbalance or hiss, gigantic effortless natural smooth flowing amazing sound
Cons: Clicks when turning on/off and when the battery runs out, only 4 hours of battery life, gets warm when running


Here I am with another amp review and this time, its of the Portaphile 627 MICRO with the stock OPA627s.
Keep in mind that absolutely everything in this review is subject to the law of Your Mileage May Vary. A head's up, as this is going to be much longer than my other review as I had far more to test it with so here's a tl;dr. 
Now that I've gotten that over with, time to continue. I just managed to catch the pre-order discount of US$439 including shipping (hurrayzaroo, US$100 off!) and I gotta say, its worth every cent I paid for it. I would've even been happy to buy it at the normal $539 price (if I didn't know about the preorder price as I'm rather cheap) as it's just so good at its job.
I paired it with just about every pair of headphones and IEMs I had on hand and some that I got to audition at joebloggs' shop (thanks for the opportunity btw NLNH). I also compared it with the Apex Glacier with certain cans. The cans that I have paired with the Apex Glacier (and can therefore compare the sound quality of both amps) are asterisked in the below list. The list is also split into the categories of portable headphones, desktop headphones, IEMs and the HD424 2000Ω version (he's a special one). Both amps were paired with the DX50 using my ZY HiFi mini to mini. 
UPDATE (5/4/14): me and my dad had a mass listening session with all our headphones on 4/4/14, so I have updated some of the headphone impressions. I've also realized that I made out the Glacier to be worse than it really is - it is still an extremely good amp.
  1. (mine) Aedle VK-1*
  2. (mine) M-Audio Q40 with alpha pads*
  3. (Dad's) HD25 ALU* (added 5/4/14)

  1. (joebloggs') Sennheiser HD800 (!)*
  2. (Dad's) Sennheiser HD650* (updated 5/4/14)
  3. (joebloggs') Audio Technica ATH-W1000 (not the W1000x as I mistakenly thought)

  1. (joebloggs') DITA Audio The Answer
  2. (joebloggs') Noble Audio Kaiser 10 (universal IEM edition)

  1. (mine) Sennheiser HD424 2000Ω (!)*

Everything Else

As I had been in England for boarding school and had the amp sent to Hong Kong to avoid import tax, I didn't have a chance to unbox the amp as my audiophile dad did that task for me. Therefore, he was the one who had the honour of listening to this amazing package first. He reports that it sounded amazing paired with his DX50 and HD650 but was too dark when paired with the HD25 ALU (opinion revised 5/4/14, please check below). As I actually appreciate a dark sound (I have the VK-1 after all), this was a great first impression for me and I couldn't wait to personally try it out.
This thing came packaged in what looks like the kind of box eggs come in, which I understand as it's an effective cost-cutting measure to do such a thing. It charges via a mini USB port on the back of the headphones. Apparently they require a lot of power input as Cesar included a double usb to mini usb cable. 
I was handed the amp by my dad before I got into the car in the way home and I was greeted by a solid hunk of metal with a potentiometer sticking out the side. Boy, was I impressed. Although the build refinement is nowhere near the excellence of the Apex Glacier's, the Glacier's unmatched in its class and the 627 MICRO impressed in a different way. While I was worried about scratching the Glacier's finish (and its scratched anyways), I had a feeling that the 627 MICRO might be the Nokia of amps in that it's finished slightly roughly but feels indestructible despite its size.
This amp does have two levels of gain (+2dB and +7dB with the OPA 627); but with all of the cans I auditioned it with, even the HD424, only the lower level was needed as its so powerful and I achieved listenable levels. I did not detect any noticeable sound differences between low and high gain, nor did I detect any channel imbalance or hiss in any of the headphones or IEMs I auditioned at my typical listening levels so that's another +1 for this amp.
When I paired the amp with the DX50 and VK-1 and turned it on, I was greeted...by a very loud click. Ouch. This immediately taught me the habit of turning on the amp BEFORE plugging my headphones in. When I wanted to switch with the Apex Glacier and turned off the 627 MICRO, I was greeted...by another very loud click. Ouch x2. This immediately taught me the habit of turning off the amp AFTER unplugging my headphones.
Finally, when it ran out of juice 5 minutes from my house as my dad did not charge it enough (4-hour battery life yay), I was greeted...by you guessed it, a third loud click. Ouch x3. Needless to say, I was a bit annoyed but after looking up the amp on the computer, I was greeted with similar reports of people experiencing the same thing. Well then, looks like I have to live with the clicks. I'm willing to put up with them though as the rest of the amp is just so amazing.
(UPDATE 5/4/14): I forgot to describe the size of the amp compared to other gears. It is, of course, thicker than the Glacier. However, when factoring in the potentiometer, it literally stacks perfectly with the DX50. It's like a match made in heaven when seen from above or below. This is another +1 in my book as it makes the already stiff potentiometer even harder to turn which means there's a lesser chance that I'll get a nasty volume-related surprise when I use the combination when out and about.

The Sound With Portable Headphones

After getting over the initial shock of the loud click, I started playing Hotel California, which is my typical reference track for, well, pretty much everything. Well, colour me impressed; this amp is small, but the sound it produces is so amazing that I couldn't quite believe my ears at first. Dynamics, bass extension, treble extension, mids presentation...everything about the amp's sound trumped the Glacier's when I played Hotel California. The 627 MICRO just sounded like a far superior, more refined amp when compared to the Glacier.
When I switched to the Q40 and listened to Shadows by Lindsey Stirling, I noticed that the bass just doesn't hit quite as hard as the Glacier and therefore this amp isn't quite as good with electronic genres of music where the music isn't nearly as complicated and bass quality and presentation is the most important. However, the bass is still of an extremely high quality and I would still be perfectly happy to have this amp over the Glacier as the Glacier is only slightly better.
(UPDATE 5/4/14): I finally bothered to try the HD25 ALU with the 627 MICRO. Man, it's another good pairing with the MICRO. I think that I can safely make the assumption that most headphones will at least sound decent with the MICRO and at most sound absolutely amazing. In addition, I no longer feel that the MICRO lacks bass. Rather, its just the right amount of bass for the song being played, as both the HD25 and Q40 have a good amount of low-end present when I played Lindsey Stirling's Shadows - my dad thought there was too much, but I can be a bit of a basshead at times. Of course, mid and treble frequencies were both represented in all their glory - the violin sounded like a violin (actually a very important aspect of presenting the music as the violin is one of her unique selling points for her music!) and everything was layered correctly.

The Sound With Desktop Headphones

On Sunday the 30th of March, I went to joebloggs' shop to audition a few cans. There, I had the simply wonderful opportunity of auditioning the HD800, W1000x, Kaiser 10 and DITA Answer.
I personally still found the HD800 to be a bit too bright with the 627 MICRO, which was the same impression that I got when I listened to it with the Glacier a while back. However, it was a much better pairing than the Glacier was as I listened the entire length of Hotel California when paired with the 627 MICRO whereas I took the HD800 off within 20 seconds of Hotel California when I used the Glacier. I also heard the famous HD800 soundstage in all its wonder, well-represented and layered in all its magnificence when powered by the 627 MICRO.
The W1000 on the other hand was a simply magical combination with the 627 MICRO. I listened to three and a half songs in a row before I reluctantly took it off to leave the shop as my dad had something he needed to do. Hotel California, Cherry Star from Hibi No Uta, So Far Away from Dire Straits and half of Rain Musique from the Symphonic Rain Vocal Album, Rainbow. The sound was simply so smooth and effortless that I forgot about the fact that my dad had to leave every time he reminded me. I was rewarded with ouch x4 as I had forgotten my newly learned 2nd habit and switched the amp off without unplugging or taking off the headphones.
The HD650 was already a great-sounding headphone when my dad and I paired it with the Glacier but it was simply taken to another level with the 627 MICRO. Again, the Glacier was trumped in every which way and the little distortion I detected when using the Glacier with the HD650 disappeared completely. It's a shame I find the HD650 to be uncomfortable as that detracted from the overall experience of listening to the music and probably made the combination sound worse than it really was.
(UPDATE 5/4/14): I've got another opinion on the 627 MICRO VS the Glacier on the HD650. Although I felt that the Glacier was trumped by the 627 MICRO, my dad felt the opposite. He said that the Glacier sounded more detailed when playing Hotel California while I felt that it sounded more pleasant with the MICRO. We both came to the conclusion that the MICRO was more 'analogue' and the Glacier more 'Digital', with both having extremely positive connotations. Also, I can safely say that our differing preferences were caused by individual sound signature preferences as I prefer a darker sound to he does - he really doesn't like the Aedle VK-1.

The Sound With IEMs

Remember what I previously said about the bass of the 627 MICRO not being as hard-hitting as the Glacier's? Well, when I used The Answer, I got bass, and plenty of it. Not to say that its a basshead IEM though, as the other frequencies were represented very well. This was also an excellent pairing and by then I've gotten the impression that the 627 MICRO can pair at least decently with everything and still get amazing results. Once again, Hotel California was well-represented 
The Kaiser 10 was the ultimate test of hiss and channel imbalance and I'm happy to report that, as previously said, neither were present. Short impressions here as I don't quite remember how it sounded but from what I remember NLNH saying, the CIEM version is far superior to the IEM version which is a bit of a shame as I can't afford 1/10 the price of the K10 CIEM.

The Sound With The HD424

Well then, a 2000Ω pair of headphones. Does the Glacier power it properly? Very much nope-ity nope nope. It sounds strident and thin with bad bass texture and overly fatiguing treble. The sign of an underpowered headphone. How do I know? Well, does the 627 MICRO do the HD424 justice? Very much yes-ity yes yes. Compared to when its powered with the Glacier, the HD424 is much fuller and actually sounds fairly neutral now. Bass is still rather lacking but quality is excellent.
The sound sort of reminds me of the NAD VISO HP50 except its much harder to drive, cheaper and far more comfortable to me. Also, its coming from a headphone made 40+ years ago. Wonderful! I listened to it for a couple hours without any issue but I replaced the pads with Technics RP DH-1200 pads which were more comfortable to me than the stock HD424 pads. To me, this slightly increased the bass quantity but did not really affect either the treble or mids too much.


CIMG0405.jpg CIMG0399.jpg
  • Like
Reactions: H T T
Great Review.  I've had my Portaphile Micro with 627 op amps for about a week.  It is amazing. It sounds expansive and full like a much larger amp.  It has great extension both high and low.   When called for, the bass is tight and plentiful.   To keep it going all day,  I connected a 5000 mAh USB battery.  I have listened with it solo and with the battery and cannot hear a difference.  
It is indeed an amazing amp and I commend Cesar on his accomplishment.
my 627 had remake its Circuit. Now it has about more than 7 hours to play. And its voice don't changed.