Most of the portable headphone amplifiers available on the market fall either to the sub $100 or the over $300 range, but with the Audinst AMP-HP, we finally have a solid recommendation in the $100+ range. The AMP-HP is available for $159.00 from Audinst’s eBay store, and though it may not offer fancy specifications on paper nor tiny minute dimensions, Audinst has succeeded in bringing another well-designed product in the market. Let’s take a look at what this amp is all about.
INTRODUCTION TO THE AMP-HP
The AMP-HP comes from the same company that has brought us the much loved Audinst HUD-MX1 desktop DAC/Amp box, almost two years ago. The HUD-MX1 may not be the groundbreaking, technical giant of a DAC. But the combination of features, usability, reliability, all packaged into a fairly affordable price has made the HUD-MX1 into one of the favorite DAC/Amp box in the market. The recipe for the AMP-HP seems to be the same as that of the HUD-MX1: a solid performing product that does the specific job it’s intended to do and offer it at a good price. At $159, the AMP-HP outclasses all of the sub $100 portable amps that we’ve reviewed. It may not offer the slim and tiny build of the $300 amps, vacuum tube amplification like on the ALO Continental amp (a review coming up), or balanced drive as in the Ibasso or RSA balanced amps. But at $159, it’s an amp that will deliver the needs of most of the portable audio users out there: a powerful, punchy sounding amp with a solid build quality. Build quality is very mature, evident from the quality of the enclosure, knobs and switches. It is better built than all of the sub $100 amps I’ve reviewed, and it even offers a better build quality than a lot of the $300+ portable amplifiers I reviewed in the Usual Suspects.
I was slightly puzzled and disappointed when I first received the AMP-HP as I couldn’t find any gain selector switch. I immediately thought that Audinst had missed such an important detail on this otherwise excellent looking amp. But as I spend time with the amp, I found out that the AMP-HP doesn’t seem to need any gain switch. I can be listening to the JH5Pro IEM, which is one of the most sensitive sounding IEM around at around 9-10 O’clock on the volume level, and that gives me plenty of control for even low volume listening. The Hifiman RE-272 IEM was slightly higher at 10+, the Sennheiser HD25-1 at 12+, and yet I can be listening to the big Hifiman HE-500 or the Audez’e LCD-2 at 3-4 O’clock. Somehow, the AMP-HP managed to accommodate a very wide range of headphones within one gain setting, very nice indeed.
GENERAL SOUND IMPRESSIONS
This is one of the few amps that I find need a light burn in for the sound to open up. Brand new, my impression of the amp was quite flat– where is the detail? where is the soundstage? Bass was good, but it didn’t have enough detail in the bass. I ran it for some 24-48 hours of continuous play (with the charger plugged in) and now I find the sound to be far more favorable. The soundstage has opened up, the details now present, and the tonal balance gives me a full bass down to the low lows, with okay mids and plenty of treble. It’s not a bassy sounding amp, but what stands out is how the low bass performance is very good among portable amps. It has a very good PRaT with the solid state speed and the bass performance combined. Very likable, if you happen to like low bass like me, but perhaps not the best amp for midrange or treble lovers.
COMPARISON TO THE JDSLABS CMOY
Among the sub $100 amps, the JDSLabs Cmoy is clearly my favorite and so I decided to compare the Audinst AMP-HP. The JDSLabs has always been a very strong performer in soundstage and in this case I find the JDSLabs to give a wider and spacious soundstage than the Audinst. The JDSLabs also had a smoother and more midrange centric sound which naturally leads to a fuller midrange on the JDSLabs. The Audinst was more of a different amp — the soundstage not as wide but deeper than the JDSLabs. The Bass was definitely better on the Audinst — as the JDSLabs have problem giving a full performance on the low bass frequencies. The Audinst also had better PRaT, through the punchier bass and overall faster pace and transients. I have to admit, despite the JDSLabs being smoother and more spacious in the sound (the JDSLabs is actually smoother sounding than many $300 amps), I find the bass performance and the overall PRaT of the AMP-HP constantly winning my preference over the JDSLabs. Not to mention the higher current output of the AMP-HP which enables it to drive the big orthodynamic headphones — something that’s way out of the JDSLab’s capability.
The AMP-HP only comes with one switch: the power on switch. There is no bass boost switch or anything like what you may find in the Fiio E11 or the JDSLabs Cmoy. However, bass performance is very solid and much better than either the E11 or the JDSLabs. In comparison with the Fiio E11, which I think has one of the best bass in the sub $100 range, the Fiio definitely feels loose and boomy in the bass compared to the AMP-HP. This is not a particularly dark amp either (unlike say RSA amps), as treble presence are quite plenty. The amount of top treble is slightly higher than what I would’ve liked, and though it is not in-your-face annoying, I would’ve liked it to be 1-2dB lower at 8kHz to kill sibilance. The voicing is definitely very good for Rock, simply in virtue of the bass — and none of the amps in the sub-$100 range can quite compete with the PRaT of the AMP-HP. Pair this with the Sennheiser HD25-1 and you got yourself one of the best portable set up for Rock. Pair this with the JH5Pro IEM and it’s even better. Pair it with the Audez’e LCD-2 and you’ll be pretty amazed at how well the little Audinst amp drives the big LCD-2 headphone. I also tried the AMP-HP with the Hifiman HE-500 headphone, and though it can drive it good, the synergy was not as good as with the LCD-2 headphone.
The MUSES 8820 Op-Amp
Although the AMP-HP comes with a socketed DIP op-amp, the stock MUSES 8820 op-amp is something I don’t see very often, and it turns out to be a very good quality op-amp. I tried swapping the MUSES with my current favorite: the OPA2227 from the JDSLabs which I found to be better than the OPA627, and the MUSES 8820 simply outclasses the OPA2227. For more details of the MUSES 8820 you can visit the Muses website here or click here to download the data sheet.
In addition to the MUSES 8820, the AMP-HP also uses the popular AD8397 op-amp on SMD form.
The AMP-HP sells for $159.00 direct from Audinst’s eBay store, which makes it quite an interesting product for the price. It’s true that you don’t get the JDSLabs’ smooth and spacious sound, but at the same time you are definitely getting better detail levels, articulation and control. The most addictive part is truly the bass section as the AMP-HP delivers one of the most solid, tightest, and lowest punching bass section I’ve heard from portable amps. Previously we haven’t had a good amp to bridge the gap between the sub $100 amps and the premium $300++ portable amps, but now I think the AMP-HP really fills the gap very well.
The AMP-HP can be bought directly from Audinst’s Ebay store for $159.00 with free shipping.
Gears used for the review:
iPod Classic 120GB, JH5Pro, Hifiman RE272, Sennheiser HD25-1, Beyerdynamic DT1350, Audez’e LCD-2, Hifiman HE-500, Sennheiser HD800.