Bakoon HPA-01M Review

Bakoon HPA-01M
Headfonics 2015



The HPA-01M’s forte is with planar cans, especially the LCD-2, which sounded positively reborn and the LCD-X which sounded so open, detailed and very coherent. This is what I love about a high-end transparent amp; a proper conduit for both the source and the cans to shine.

Audeze LCD-2/X

(Paw Gold line out)

The LCD-2 bass response is coherent, detailed and full sounding when paired with the Bakoon HPA-01M. Vocal presence is clear, natural and engaging and whilst treble on the LCD-2 Rev 2 is never going to be the strength, it does indeed sound very smooth and sibilant free.

Granted the LCD-2 is not a soundstage monster but the engaging lush tones and liquid flow of the match with the Bakoon will suck you right in. The Bakoon hides nothing. It simply reinforces, adds some juice and a touch of pace.

The Lotoo Paw Gold DAP may not be the most dynamic of DAPs but amped, line out and running out of that flat neutral and speedy Bakoon current drive output it sounds positively brimming with musicality using the LCD-2 rev 2.

The amp in the Paw Gold is one of the stronger ones in the portable range but it is not on the level of the Bakoon. The Paw Gold with a straight connection to the LCD-2 sounds smooth and natural but lower in dynamics and a bit too polite. The Bakoon gives it a nice edge, beefs up the sound considerably but still conveying that smooth and liquid tonality of the Paw Gold.


The LCD-X has zero power issues when matched with the Bakoon (Paw Gold source). It can drive these effortlessly without any clipping or distortion. That elevated and cleaner treble of the LCD-x really shines with the neutral and energetic sound signature of the HPA-01M.

The speedy nature of the HPA-01M also matches perfectly with the faster transients of the LCD-X and the quickened decay especially in the midrange and lower treble without a hint of any unwanted glare or sibilance.

Switch over to voltage drive in both the LCD-X and LCD-2 and you get a slightly warmer and greater emphasis on the lower mids and bass weight. The pace drops a bit compared to the current drive but you get a slightly weightier or fuller response. The treble still has great detail but the articulation is a bit slower. For some, this might be a welcome change to the more linear speedy current stage and a better match for modern pop and rock.

Oppo PM-1

(DX90/Paw Gold line out)

When paired with the Oppo PM-1 the output in current drive was lean, clear, speedy, the bass is a bit more linear than before, speed is much improved and the DX90’s dynamics intact. The smoothness of the PM-1 and clarity of the DX90 mesh well but the power of the Bakoon helps deliver a very detailed and rich sound. The pairing at all times remained sibilant free with excellent control.

In current drive the low-end weight of the PM-1 has been pulled back ever so slightly in favor of detail and speed. Combined with the new Oppo PM series leather pads the increase in speed and better treble performance works fantastically with heavy rock and metal.

Nile’s “When my wrath is done” steel guitar and chugging riffs intro sounds crisp clear and incredibly well defined on the PM-1. The Paw Gold/PM-1 with the Bakoon was far more impactful than the DX90 pairing and slightly more musical.

The PM-1 low end just sounded that bit fuller and vocals more natural. Naturally, given the PM-1 super efficient design, there were no issues on power with both DAP’s but high gain felt the more natural of settings with the Bakoon on current gain even thought the PM-1 is relatively easy to drive.


(Source: DX90/Paw Gold/Shanling M3/FiiO X5)

Going beyond the initial low volume imbalance problem the HPA-01M showed a welcome degree of flexibility and excellent pedigree with the majority of IEM’s.

The HPA-01M is blissfully noise free and retains a lot of the detail, speed and control I found with the planars testing. Power on low gain was manageable and the pot had some give in it before it got too loud for use with sensitive earphones.

Balanced Armature

Interestingly I found the current drive to respond quite differently with BA as opposed to dynamic drivers. In most cases with BA drivers the output followed the same path as planars with a focus on speed, clarity and a neutral sound signature that was quite linear.

Whether it was four or 8 drivers the dynamics of each IEM stayed true to that reference signature. BA’s test included 2 customs, the Harmony 8, Visions Ears VE6X and the more midfi Westone W4.

Vision Ears VE6

Visions Ear’s VE6X was an interesting match. Tonally it was neigh on perfect but the VE6X has a habit of making any amp sound excellent and the HPA-01M is no different. What I did notice was the hyper sensitivty of the VE6X to pot adjustments with a slight bit of noise or ‘scratch’ when moving the output up slowly. Very curious indeed but not invasive during listening sessions. I ask Soo In Chae what would cause the scratch:

“I’d like to share my feedbacks first regarding about the noise/scratch, it is actually a small amount of DC leakage noise at the initial start-up. Since the HPA-01M is a zero negative feedback amplifier (quite possibly only portable one in the world), there will be a minimal/small amount of DC leakage for the first few gain controls, but it will be completely gone afterwards as the circuit is then more “stabilized” without any DC output. This is also stated in the manual and you will notice that there will be no noise after you control the knob a few times.”

Custom Art Harmony 8

Custom Art’s 8 driver BA Harmony 8 has a warm, smooth and slightly laid back or rolled off top-end so any emphasis there is more than welcome. For source matching the DX90 and the Shanling M3 was a bit cleaner and clearer with the Bakoon pairing than the Paw Gold or FiiO x5. The treble performance sounded more articulate and less shelved down.

Westone 4

The Westone 4’s BA setup was a bit harder to drive than the dynamic drivers we tested on the Bakoon/DX90 pairing. The current drive output with the W4 on EDM was much tamer but more balanced, coherent and reference level. The BA setup can’t really match the slamming power of the dynamic bass head T10i. This is a return to a flatter detailed sound with an emphasis on detail and control over dynamics and power.

Bakoon HPA-01M

Dynamic Driver IEMs

When we switched to a few dynamic IEM’s the current drive output added more of a low-end emphasis with the IE800 or in the case of the RHA T10i, it went into a ballistic bass head mode with one of the strongest yet well-defined bass responses I have heard in a dynamic driver.

Granted both these IEM already has a well-defined bass response but driven with the DX90 as a source and the HPA-01AM there was a surprising boost. Dynamic IEM’s included the flagship IE800 and the lower mid-tier RHA T10i.


The RHA T10i with the DX90/HPA-01M match was incredibly powerful especially for EDM, moombahton and electro house using the current drive ouput. The T10i’s treble filter bass performance was powerful, heavy-hitting yet the definition and control were still there.

If you want to hear a set of lower mid-tier IEM’s known for bass hit one out of the park then try this pairing with Major Lazer’s “Wind up”. An incredibly deep and hard hitting bass but not an ounce of it was sloppy, boomy or muddy. Mids remained clear and spacious also with plenty of width even during those hard hitting sub bass moments.

The DX90 clean clear tonality and heavy-hitting dynamics combined with the power and speed of the Bakoon might be overkill for some on the T10i, especially on voltage drive output but for bass heads, this is my enjoyably exhausting top choice.

Bakoon HPA-01M


Whilst not doing away with the inherently brittle treble the HPA-01M did control the IE800 much better than most amps. Right away, and especially with hi-res via current drive output, you are going to notice the articulation and detail as well as just about every speck of that big soundstage being utilized.

Pairing the IE800’s with a smooth source and the HPA-01M and run Pink Floyd’s 2015 “Night Light” (DSD128) and you will get a great mesh of the IE800’s renowned detail and the Bakoon reference level speed and clarity.

On the Voltage drive, I found the volume had a touch less room to play with. Optimal output level came far quicker and if you are not careful you can get an uncomfortably high level quickly. Again the characteristics of this drive came through loud and clear; heavier bass response, slightly warmer tonality, a little bit more musical but slightly smoothed out reducing the speed and detail compared to the current drive output.

I was a fan of this drive on synth hard rock such as H.E.A.T’s “Living on the run” using the IE800. Rhythm guitar and bass work sounded suitably thicker against a lower treble deluge of 80’s style synth. That added weight was really something any serious hair metal guy needs I promise you that.


Lotoo Paw Gold

DAP matching with the HPA-01M was a really interesting journey. Each DAP’s core sound signature was always present and distinguishable when amped using line-out. The Lotoo Paw Gold was my top choice for pairing with the HPA-01AM.

The Gold’s amplifier is one of the strongest in the portable market today and had no such problems driving Audeze’s planar range on line-out with plenty of power on tap at a much lower volume level than the other DAP’s tested with current drive and voltage drive.

The Paw Gold was full sounding, smooth with great vocal presence and a treble range that was very natural and engaging. Vocals are slightly more forward on the Paw Gold than the DX90 which by comparison was a bit more distant and arena like in its presence.

Ibasso DX90

In comparison, I really had to yank the power up on the DX90’s weaker line out performance even when on its high-gain setting to get a decent volume level that could match the Paw Gold line out into the Bakoon’s current drive output.

Headphone out was much worse at around 240 volume to be able to match the same volume setting as the Paw Gold was achieving when paired with the Bakoon. I also had a slight preference for voltage output than the current drive with the DX90 given the voltage drive had a slightly higher gain setting than current drive as well as a slightly thicker sound which paired better with the leaner DX90.

Bakoon HPA-01M

Shanling M3

Using the Shanling M3 power matching on the line out was closer to the Paw Gold with a smidgen more volume but better dynamics, more like the DX90 level of dynamics but a little bit of an edge taken off and less bottom end weight. That linear and tight bass response is there, the musical and fun signature is properly conveyed and that clean top end never once sounds veiled.


The AK120 pairing sounded smooth, natural, and fuller than the DX90 though not as full sounding as the Gold. Power from the AK120’s headphone jack was also an issue compared to the Paw Gold.

In much the same manner as the DX90 I had to push the AK120 up all the way to full to match the line out of the Paw Gold. Paired with the Bakoon it also does not feel as planted and rich in the low end as the Paw Gold but had a similarly smooth and natural signature in mids and treble.

Bakoon HPA-01M

Our Verdict

It is rare these days to get very excited on pure portable analog portable amps due to the increasingly sophisticated and great sounding convergence DAC/Amp’s coming out today at great prices but the Bakoon HPA-01M is one such amp that I think is a force to be reckoned with.

The matching with planars is sublime and addictive, particularly with the neutral speed demon current drive output. Yes, your source needs a good output if you wish this to remain a portable delight and chances are you will want a high-end source at that to take full advantage of its capabilities but lower-end DAPs sound more than capable.


A small caveat is the Bakoon HPA-01M low gain ouput channel imbalance particularly with IEM’s. That is unavoidable sadly with highly sensitive gear in general with the HPA-01M. However, once you are in full throttle that concerns ebb away and the HPA-01M sounds fantastic with one or two we tested.

I particularly enjoyed the dual flavors of voltage and current as viable listening options depending on the tracks in play and heartily recommend your DSD to flow through current drive and lossy modern works to veer to the slightly more colored and fun Voltage output.

One thing is for sure if you are a planar guy and in particular, an LCD series owner the HPA-01M will sound really magical and will give plenty of high0end desktop systems a good run for their money. They are made for each other both on a power level and performance level.

Bakoon HPA-01M Technical Specifications

Input 1 Voltage (3.5mm Mini Jack)
Input Impedance 10 KΩ (Voltage)
Output Current / Voltage (simultaneous)
Gain High / Low switchable (current output only)
Maximum Power Output 350 mW (32 Ω, 1 kHz)
Frequency Response 10 Hz ~ 1 MHz
Battery Type Li-ion
Battery Operate Time Up to 8 and a half hours
Battery Recharge Time 2 hours (80% capacity) / 4 half hours (full capacity)
Dimensions 95 mm (W) x 140 mm (D) x 17.5 mm (H)
Color Finish Black, Silver, Gun Metal
Shipping Weight 1.0 kg

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