Now the amp is what they call a “Current Mode Amplifier” …. with this being one of just two amps to use this technology as the Bakoon HPA-21 also uses it but I think does it in a slightly different way.” Sonny Trigg, Dec 2013

No longer is the CMA800R just one of two, nor is the only one in my collection. I am of course referring to amps using current mode technology. It is certainly becoming less underground with my VicJohn Audio VX-1 arriving any time but I still wouldn’t go near saying it was common. Of course Questyle were my introduction to this approach to headphone amplification, the first company to implement this were Korean outfit Bakoon. Back when I wrote that quote it was the lone HPA-21 in Bakoon’s personal audio range but since then we saw the HPA-01 and then… we got this. Trust me there is more changes from the desktop HPA-01 than an added M, but from that M we really get the jist of why the changes happened. Yes Bakoon wanted to mobilize the 01. The 01 wasn’t the biggest to begin with so the most obvious change was to get it unhooked from the wall and a Li-Ion battery with a quoted 8 hours should do just the trick.


There is Style with this One

With the Li-Ion battery under the hood we can take this were we want. But we didn’t stop there with the changes, although in terms of functionality the biggest differences are the RCA inputs being swapped to a single 3.5mm jack (this is all analogue) and some components being changed to get this smaller, the most obvious differences are the aesthetics. We still have the same Bakoon special in the Satri circuit which the most important thing. From what originated as one of the blandest amps I have ever seen, this blossomed into a real swan. For a start you have 3 options in terms of colour, the standard black, a gun metal and finally silver. I have silver and I am glad, it sits nicely next to the duralumin of my AK120 Titan. Oh and while in this paragraph, another cool design idea is how it clearly says, “use me with your DAP”. On either side of the amp you have an amp band, that with a slight movement will easily secure whatever portable player you may have.

While it may have been shrunk and look great, the size is something that leaves me a little unsure. That’s the fact it still isn’t small. Portable audio is pretty disillusioned these days and I think this is one of the reasons why. I just wish this was smaller, ok maybe I am asking for the impossible. Bakoon quote “audiophiles on the move”? For me on the move is me putting one foot in front of the other and going somewhere and I don’t see how I can comfortably do that with the HPA-01M. It wont go in my trouser pocket, or my blazers for that matter and I don’t want something that’s $1295 being thrown around at the bottom of my messenger bag. So yes I am happy to put it in an Otterbox and boot it up wherever I may need but on the move this is not, unless you seated cosily on an airplane, where this can rest comfortably on the tray in front of you. While I am being bitter about its portability, this amp does flirt with perfection for something that you can take anywhere and that’s the reason we are going to keep looking at this with the upmost attention.

I do like the ergonomics of the amp as well, with the 3.5mm input out the way on the top, charging port on the side, and then all the stuff to play with down the bottom. Down under and the first switch we have it the power, followed by a gain with high and low options (which is only for use with the current mode output) and then you have both a current mode and voltage mode 3.5mm output. Finally you have a volume put that is seated under a hood so you can only just get to it, a little finicky and doesn’t have great knob feel, but most importantly, if you were on the go this wont get knocked and I think that justifies the design more than enough.


So current mode, that’s like the Questyle CMA800R you mentioned earlier? Not at all, the technologies are very much different and I have had the mines better argument from both companies and for that reason I am not even going to talk about the technology any more, both are interesting and very unique in their takes of amplification and I think that is the main point you need to take, they are doing something far from generic, in my mind neither is better and they sound completely different.

The Output Impedance Effect

You just can’t get away with this thing can you these days. The hand output impedance (OI) plays with this amp is how it makes different types of headphones sound.  You see the current mode output is quite high in impedance so depending on an impedance plot of a headphone or IEM, different frequency ranges will get different gain and therefore effectively, it will skew the frequency response of some headphones. Now when I say quite high I am being polite. Look at a lot of new products and they strive for under an ohm OI and something like the original AK100 with 22 ohms OI is considered way too much and I among other heavily criticized it. Well the current output has close to 1 mega ohm OI and just in case you didn’t know, a mega ohm is a million ohms! The voltage mode output is much lower (near 1 ohms like you would want) and therefore doesn’t suffer at all and will always allow you to get your headphones true frequency response.  Now glance around a few reviews of this amp and you will see how people talk about the current mode output of this amp being revolutionary and the likes for planar magnetic headphones. The reason for this is that planars have much flatter impedance plots than any other type of headphones so they get no change or equalization, just great amplification. Plug in something that has huge impedance swing like a custom in-ear monitor with multiple balanced armature receivers, say 10 like my Heir Audio 10.A, which ALL have different impedances and you get something that sounds hugely different to the voltage output and ANY other amp in my collection. Now what does that mean for the current output and headphones that aren’t planar magnetic, well it can mean anything, it can mean a synergy that you would die for or something that makes you want to puke your guts up, but in most regards, you are going to get some sort of frequency response change.

Now another thing this must have if it is supposedly good with planars is power. Now it has less than the original HPA-01 and also less than I expected at 350mw, which in my mind just can’t power some of the hungrier planars like HiFiMAN’s HE-6 but I can’t comment either way personally. Obviously with a lot of power it is fair to wonder if this too much for IEMs and I would say no, not at all. It isn’t dead quiet in background and you also have volume even with the pot at zero (as well as channel inbalance) but once you get to listening levels the channels are balanced and the sound is nice, I have taken this amp out with IEMs in mind on a regular basis.

Getting to the Bottom of How This Sounds

Dynamics –

As I said in the last section you can get a lot of different types of performances out of this amp depending on what you choose to use this with.

With dynamic headphones of both high and low impedance I tended to find the current mode to be quite bassy and thick. With a lot of emphasis on a slow and creamy mid-bass that was very comfortable. The sound is also very powerful, there is a real oomph behind it, some meat and an engine. While I find the mid-bass easy I do still find the current output to be very fast and capable. The soundstage is huge as well, very big in all dimensions although I must say I find it a bit blotchy, everything is spread out but instruments don’t seem to hold a natural and blended image. Everything has almost to much individual space.

Switching to the voltage output and I always found things to brighter, that was always the initial and most obvious impact. Along with that we had a weaker but tighter bass response and everything is a bit colder and thinner. We have incredible pace and awesome detail as well.

I must say I find the current mode output more powerful, it drives high impedance stuff with much better ease, take the HD800 or example I compared the two Bakoon outputs with the Questyle CMA800R. In terms of sheer tonality I would put the Questyle in the middle with the Bakoon outputs either side. The current mode was powerful, dynamic, very laid back and smooth in the treble with a ferocious bass response, something I can enjoy paired with the more articulate and agile HD800. The Voltage output was horrible though, shrill, weak, messy and with no control over the drivers. It struggled.

With my much lower impedance Beyerdynamic T5ps however choosing a Bakoon output became a lot more personal. I swayed too the voltage out with these as it was more controlled and a little more aggressive. That being said the current output was potent and addictive with a more relaxed treble and thicker, more rhythmic bass, similar differences to the what I found with the HD800, but more control with the voltage out. Being strictly honest, I did find a preference with the voltage output with most dynamic headphones and IEMs for that matter. IEMs on the odd occasion were nice from the current jack but on a lot of occasions I just found some real anomalies in the frequency response due to the output impedance and the voltage output just suited better because of this.

Planar Magnetics –

It is like the outputs switch roles now with the flat impedance plot of a good planar. Now the current mode is the sensible one, the more sterile one, that one with obvious treble and Usain Bolt like speed. It actually makes the voltage mode sound a bit chilled out and I will cut to the chase, I don’t think you will use the voltage out along with any planar, it just didn’t seem to offer a benefit.

The current mode output is now a thing of transparency, you hear the source, you hear the music, and it delivers all the juice you may need into my extremely thirsty ZMF Blackwoods and the much more efficient Audeze EL-8. In fact the EL-8s shine very bright with the Bakoon, much more so than any other headphone I have tried with this. I don’t like the EL-8, I don’t know what Audeze were doing with it and for the most part, it isn’t great sounding, but if you do want it, then the Bakoon is the only way to go. While I find the effects and capabilities of the amp are extra dramatic with Audeze because it actually gets them from meh to decent, the ability is still clear with the likes of my Blackwood. These things are notorious in their own right and sound coherent, balanced and oh so fast with the Bakoon. The ZMFs are fast and detailed as it is but I find this combo ready to take on even the most difficult and treacherous passages of music. I also find dynamics effortless, everything is powerful and big, and then the little nuances, the micro details, the little breaths, they are there under a microscope. The only thing I am not a huge fan of is the blotchy soundstage I mentioned earlier is still there to my ears with planars. I must add though that the soundstage is dead black, hence everything has so much space.

There really isn’t a lot more to say about its sound here because it is so on point, it is that glass portal you want to you music with the authority you need it to have, nothing more. Give it a warm DAC and you will hear that, give it a DAC with a great soundstage and you will get that as well, nothing more, nothing less.

It Does Have Its Place

Because of its size and some other things I wasn’t sure it would but after living with it, I have no doubt about this. Its combination of interesting effects on different headphones and stellar planar synergy just make it worth owning.  It has its flaws, it gets a little warm, the headphone jacks could be better quality (plastic inside) and yes it could be smaller but if you’re a planar owner who needs and amp to take abroad, to work, on a trip, this is as good as it gets, quite bluntly. While acceptable with dynamics and IEMs, I wouldn’t say this is an easy recommendation, not at the price, you can definitely do better cheaper, I prefer both my Leckerton and Vorzuge with IEMs and the risk of the current modes output impedance may not be worth it with dynamic drivers, I would stick with something less risky. With a planar though you should be risk free and for that reason I am ecstatic with what Bakoon have produced in the transportable realm here.

Sonny Trigg