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[mini shootout] Desktop amping solutions for the HE-6: Nuforce Icon2, STA-100, and CEntrance DacMini PX

post #1 of 16
Thread Starter 



It's no secret that those seeking to amp the HiFiMAN HE-6 will veer towards speaker amps. However, it seems the more recent trends have been moving towards beastly current driven 100W monstrosities. That's cool, I've got no problems with that. I've played around with my fair share of speaker amps too. Some sounded great, others were awful. I'm currently of the opinion that more power does not equate to better sound, and that component matching plays a far heavier role.


In any event, that's not what this review is about. Since I acquired my HE-6, I've been searching for a nice desktop amp to power them. That means it has to fit in with all the other junk on my desk, so one of the primary considerations here is SIZE, or rather, size.


That brings me to the three contenders that I've got with me today, in brief:

#1: Nuforce Icon2: 6x4.5x1” (roughly a paperback book), usb and line inputs, 24W ($350, amp only equivalent at $180)

#2: CEntrance DacMini PX: 6.5x6.5x1.6” (roughly a hardcover book), usb/optical/coax in, line in/out, 50W, (msrp $1k)

#3: Nuforce STA-100: 9x8.5x2”, amp only, 160W (msrp $700)


I tried to keep things as consistent as possible in terms of components, but in the end there was just too much cable juggling. I may have tried to use the same dacs in between each, or the same preamp, but whatever. I will list out the systems as I used them, plus any accompanying notes when I switched things around.


#1: Nuforce mini-stack:

- Icon2: serving purely as amp - separate review here: [link]

- HDP: serving as dac, fed spdif

- LPS-2U-192K: upgraded power supply, dual output for both the HDP and Icon2, plus usb/spdif bridge

- RJ45CX: converter box for RJ45 into binding posts, further modified with a 4-pin XLR


#2: CEntrance DacMini PX - review in progress

- mostly used on its own

- primarily fed spdif from the LPS-2U-19K

- using a banana/XLR4 adapter I made


#3: Nuforce big stack:

- DAC-100: serving as dac, fed spdif - separate review here: [link]

- HAP-100: preamp - separate review here: [link]

- STA-100: power amp, using a banana/XLR4 adapter I made



Nuforce Icon2


So let's start with option #1, my mini Nuforce stack. I'll admit to some sentimental attachment to this one, as all the pieces came together slowly and I really enjoy the synergy of the whole system and the flexibility that it offers. Now, at the very beginning all I had was the Icon2 by itself. On it's own, I really do think it's a fantastic piece of kit, and probably the best all-in-one unit for the size and price that you can get. Seriously, this thing as a speaker amp is smaller than most other headphone amps I've tried, nevermind that it has a dac and some preamp capability as well, oh yeah and a regular headphone amp as well (which is nothing special, but hey it's there).


In terms of sound, it kicks a lot harder than I would have expected. The sound has a nice “groove” factor to it, with a bit of emphasis in the midbass which gives some thumpin' energy, but doesn't quite have the impact of the STA. Its weak points are in soundstage and definition. The stage is somewhat narrower with the Icon2, and is so-so at depth. The sound never suffers from the “in your head” syndrome however, which is a good thing.


Definition is good, I can't complain really, it's just the PX and STA do it better. Simple as that.


Where the Icon2 wins handily is in background noise, besting the other two quite noticeably.


In terms of power, I can barely make it past 12 o'clock before it hurts my ears. As the weakest amp in this shootout, I don't think power capacity is ever going to be an issue here.


So that's all with just the Icon2 by itself. Once we start upgrading along the chain, things improve. The HDP has been around for a while now, and there are plenty of reviews on head-fi so I don't need to get into that here. Needless to say, the HDP dac is better than the Icon2 dac, no question. Moving on.


Adding the LPS into the mix, ah well this gets interesting. The differences from power supplies can be very subtle, though in my opinion it is critically important to a good system. So that said, does it make a difference here? I would say a definite yes. Just on it's own feeding into the Icon2, the difference was small and helped flesh out the bottom end with some more energy. Just on its own feeding the HDP, definition improved a very small amount, almost imperceptibly so. Putting it all together though, feeding clean power simultaneously into the Icon2 and HDP, well now that's a different game altogether.


Overall definition and clarity improved, while retaining some of the oomph in the lower end that makes this my favourite “fun” amp for the HE-6. While the PX and STA may still win out in technicalities, the gap now is very small and the Icon2 still has that groove that keeps me engaged.


If going with the combo stack here, I'd actually recommend picking the Icon amp instead of the Icon2, as you will not need the built in dac and the binding posts will be far more convenient than the RJ45 outputs of the Icon2.


Total cost for an Icon + HDP + LPS would be roughly $1.1k, which is just a shade more than what the PX costs by itself. You can find HDPs fairly often on the used market as well, which can bring costs down.



CEntrance DacMini PX


Unlike the two Nuforce stacks, the Dacmini PX stands all by its lonesome. It is smaller and slightly cheaper than the Nuforce mini-stack (though significantly larger and more costly than a lone Icon2), with the same set of inputs/outputs and the bonus of a class A headphone output.


Compared vs just the Icon2 by itself, there's no contest. The PX is a class above in all manners technical. Compared vs the mini-stack, the differences are smaller but the PX still edges out.


The detailing is excellent, coming nearly on par with the bigger Nuforce stack. The treble feels a bit softer, but the articulation is better which makes it easier to distinguish, and the clarity lends to a fuller feeling sound. So while the Icon has more groove in the bass, the PX is cleaner.


The staging is perhaps the widest of the three, but does suffer a bit from the “in your head” feeling which the Nuforce brothers do not have.


In terms of overall tonality, the only word that comes to mind is neutral. It's there, it's clean, it's succinct... yet somehow it doesn't engage me as strongly as the Nuforce offerings.


I find the best music to pair with the PX are the acoustics with soft definition, where the clarity of the PX brings them out with a gentle hand. I would have thought that the softness would help tone down some aggressive recordings of rock or metal, but it just didn't jive. Instruments, orchestral, and vocals are the definite strong points.


I did not hear any difference switching between usb and optical/coax inputs. Something that bears mentioning though is that I had problems with the PX freezing if I unplugged an input while it was on. The only fix for this was to unplug the power and plug it back in. Granted, you really shouldn't be yanking out cables when a device is running to begin with, but I just thought I'd mention it. I also got the occasional clicks/pops over usb, though was never able to track down the cause of that.


Volume wise, much like the Icon2 I can get to around 12 o'clock before it becomes too loud. Actually, I can go a bit higher sometimes, which is puzzling since the PX is supposed to have a higher power output. My guess is that the pot just works on a slightly modified scale. The PX is not dead silent in terms of background noise, but it's pretty darned close. It's absolutely nothing to worry about when you have music playing unless for some reason you have it cranked all the way.


I suppose I should mention something about the PX headphone output. It's very good. Yup. Is it better than the HDP headphone output? Yep, just barely. I could be perfectly content with either one. Both have a warmer tilt to them, and plenty of power on tap for regular headphones.


I don't think I've ever seen a used PX up for sale, so you'll probably have to find one at regular retail.



Nuforce STA-100


Last but certainly not least, we have the big Nuforce stack. The STA-100 is a fixed amp, so you need a preamp or a dac with variable output to feed into it.


So the Icon2 is the groovy one, and the PX is the neutral one, where does that leave the STA? It's the one that grabs you by the throat and demands that you pay attention to it. It doesn't engage you, it cracks a whip. It's not gentle, it's not subtle, and it doesn't take no for an answer. This makes the STA exciting to listen to at first, but it has such a presence that... I'm not sure how to describe it. It's not quite the same as fatigue, but there's this energy to it that you have to be in the mood for. Some people relax by getting a massage, others relax by going to the gym. This is the latter. Boot camp.


The sound has a slight V shaped feel to it, giving the most impact of the three. The treble is slightly hard, though eases up a bit as the amp warms up (when I first listened to this amp it was still cold off the delivery truck and sounded *awful*, but improved dramatically once it got warmer). The bass runs low, really low, and positively growls without becoming blurry. In fact, I would say the bass definition is the best of the three. The low end textures are excellent and well defined. The STA likes to play hard, and the louder the better.


My initial thoughts were that the amp had rather lousy soundstage, but after a bit of testing I discovered that the speaker outputs are actually labelled backwards (this should be remedied in future batches). Well, switching things around and voila, all is right. Stage depth is the best of the three, and while not as wide as the PX it places the centre image around you rather than in your head.


The STA runs the hottest of the three. The Icon2 and PX barely produce any heat of note, while the STA feels like it runs a few degrees above body temperature. The DAC/HAP/STA-100 stack is runs a few degrees higher yet, though nothing compared to the Asgard or Valhalla.


The weak point of the STA is the noise floor. With no input, there is a soft background hiss. I'm not too surprised at this though, as it's the strongest amp of the three and does not have any internal attenuation. With music playing, the hiss is only noticeable during very soft acoustic passages. The hiccup with the high gain though is that it absolutely requires a dac with a very low noise floor. Something to consider when matching components.


Featurewise, there are none. Unlike the Icon2 and PX who have a host of options, the STA has an RCA input and speaker outputs, that's it. The power switch is also on the back, so you'll have to reach over if you want to turn it off.


Performance of the entire big rig is a step up from the PX, but not by much. The Nuforce-100 stack has slightly better microdetail and is more engaging overall, has more input options, a lot more power, remote capability, and finer volume control. It loses out on noise floor, is much much larger, more expensive (double the price of the PX), and doesn't have as good of a standard 1/4” headphone jack.



A note with speakers


Since these are in fact speaker amps, some notes regarding their performance with speakers seems apt. I already wrote about the Icon2 + S-X in a previous review, so the notes here are primarily between the PX and STA with the CEntrance Masterclass 2504 desktop monitors and an old pair of average efficiency Paradigm bookshelf speakers.


The PX for the most part shares a similar sonic characteristic as it does when driving the HE-6, though I would say its performance is better with speakers. The treble loses some of that soft touch and gains some bite to it, adding some energy into the music. Spatial depth is also much better than before, pulling things into focus that I didn't even realize were blurry before.


With the STA, the sonic characteristics did a big flip. Where they were aggressive and demanding with the HE-6, they have a very soft touch with speakers. Almost gentle in fact. The energy is still there, especially through the bass, but not as angry as before. The soundstage is also very very wide, now besting the PX. The noise floor was just barely noticeable from a foot away with the 2504, and not at all with my Paradigms. Unless you're using super efficient monitors right next to your ear with a noisy dac, I don't think noise will ever be an issue here.




All three have more than enough power for the HE-6, with technical chops on par with big full sized speaker amps that I've tried.


Nuforce Icon2:

- *tiny* all-in-one box with dac and preamp capabilities

- not the most proficient, but relaxed and engaging sound

- groovy bass, smallish soundstage


CEntrance DacMini PX:

- a better all-in-one, but bigger and more expensive

- sonically very neutral, slightly dry

- wide but short stage


Nuforce STA-100

- amp only, no functionality or even volume control

- aggressive and gripping, slight V shape

Edited by Armaegis - 8/22/13 at 3:46pm
post #2 of 16
Thread Starter 

pictures coming soon!


edit: actually here's the main picture for now. Behold my super clean desk. Actually no that's not my desk, that's the dining room table that I took over so I could have everything set up simultaneously.




On the left of my laptop, top to bottom: (not counting the iBasso D10 obviously)

Nuforce DAC-100

Nuforce HAP-100

Nuforce STA-100


To the right of my laptop, top to bottom:

(black) Icon2

(silver) HDP

(black) RJ45CX



further right:

CEntrance DacMini PX


At the back:

CEntrance Masterclass 2504 speakers, on my super high tech phone book/cookie tin/3-ring binder speaker stands



adapter: banana post to 4-pin XLR; 4-wire braid stranded copper and sleeved

This is my banana to XLR adapter. Pretty standard 4-wire braid, sleeved in paracord. Sitting atop the STA-100




another view of the "Nuforce Towers" as I have dubbed them

Edited by Armaegis - 5/30/13 at 7:04pm
post #3 of 16

Nice shootout. I'll come back to this later but wanted to say that it's interesting you chose amps that are Class D topologies. :)

post #4 of 16
Thread Starter 

It wasn't an intentional choice, but when going for small size in a power amp they'll usually wind up being a class D or T. Some other options that I would have liked to try would be the Travagans Red/Green, Firestone BigJoe/Rubby.

Edited by Armaegis - 5/31/13 at 3:25am
post #5 of 16
Thread Starter 

Just for interests sake, I've tried the HE-6 from the headphone outs of both the HDP and PX (which should be the same as the CX; also note that mine has the 1 ohm output mod). Both go reasonably loud; not earsplitting, but enough for a good  head throb. Also absent was any clipping at full volume playing sine waves at -0dB line level. The HDP was looser and didn't have as much control as the PX, though on the flip side this did give the bass some more body. However, the HDP does have a 10 ohm output impedance, so the damping factor is lower which could easily account for this. Or maybe it's all placebo since it's not a direct comparison. As I do not have a Dacmini with non-modded headphone output, I can't compare directly.


They felt roughly the same volume, though with the looser bass on the HDP it "felt" louder. I'm not really keen on testing maximum volume here, as I value my hearing. It is above comfortable levels for me and doesn't distort. Not shabby at all. 

Edited by Armaegis - 12/22/13 at 5:56pm
post #6 of 16

With your speakers - how would you describe the difference between using the HAP as pre-amp and simply skipping the HAP and just running the DAC-100 as pre-amp?

post #7 of 16
Thread Starter 

I only did that briefly, but it sounded just fine to my ears. The HAP is sufficiently transparent that it doesn't change how anything sounds. It provides flexibility for analog inputs and a finer  volume control. 

post #8 of 16

Thanks. In that brief time, were you able to note if the HAP pre-amp was a fair step up from the DAC's pre-amp?

post #9 of 16
Thread Starter 

I'm not entirely certain what you're asking... I could not hear a difference going directly from the DAC-100 or going through the HAP-100. If you're talking about their switching ability, that's kinda moot since one is for digital inputs and the other is for analog.

post #10 of 16

Sorry to be unclear, but yes - I mean the difference if you went directly out from the DAC-100 to your power amp (or active speakers) compared with going from the DAC-100 to the HAP-100 and then to the power amp (or active speakers). You already answered that now though, so thanks :)

post #11 of 16
Thread Starter 

I just recently acquired a FiiO e17 and a1, their portable dac/amp and speaker amp (now discontinued). I must say, the a1 for $80 is a dandy little thing. With the e17 this is a <$200 combo with a lot of versatility. If I didn't have all my other toys, I could be satisfied with just this (heck I'm tempted to find myself an e09k just to round out the stack... anyone have one they want to trade to me? :D)

Edited by Armaegis - 11/5/13 at 9:13pm
post #12 of 16

Per your PM, Nathan, we do need to add the TBI Audio Millenia MG3 in this roundup!   :D


32 Watts into 8-Ohms on 24VDC external PSU or battery

10 Watts into 8-Ohms on 12VDC extenal PSU or battery (or using eight AA batteries within its internal battery compartment)




post #13 of 16
Thread Starter 

Do you think there any other class D/T amps I should be looking into?

post #14 of 16
I have no experience with any others, but I've read that the MG3 does not exhibit undesirable treble traits common to other class D amps. As to the Tripath amps, I have no "hearsay" to contribute.

post #15 of 16

Look into the Burson Timekeeper, it may be something you are looking for. You may also try the schiit mjolnir.

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