Resonessence Labs Herus USB Headphone Amp/DAC Page 2


In the House
The Herus is impossibly small—pictures don't really do justice to the true scale of this little thing. It's almost hard to even take it seriously—though the solid build quality helps to some degree. The Resonessence Labs Concero family of DACs is already very compact but the Herus is a whole different thing altogether. I started with my desktop system, swapping out the Concero HD which had been feeding the Adam Audio F5 active monitors. I used a vaguely fancy 1/4" to RCA adapter along with my existing RCA cables, just because I had one laying around. You could just as easily use a cheaper one if you prefer. Or if you want to go higher end, you can probably contact most any boutique cable maker and have them whip up a custom cable with the proper termination on each side.

I was able to effortlessly play my entire collection—from lossy tracks to Redbook quality to DSD128 and everything in between—without a hiccup. In that respect the Herus is what I'd call "functionally transparent". It just played everything, with no objections in the form of relay clicks or other tomfoolery. The difference in sound between it and the Concero HD—at more than twice the price—was not immediately noticeable. That's high praise indeed and a very good start to this evaluation. The Herus was neutral and fairly resolving without overdoing it, allowing a nice sense of space when paired with the Adam monitors and their X-ART ribbon tweeters. At the same time, recordings that I wouldn't exactly call "audiophile quality" did not have their shortcomings laid bare. I'm talking "Hey Ladies" by the Beastie Boys, "Triumph" by Wu-Tang Clan, or pretty much anything by Red Hot Chili Peppers. It was definitely a solid performer, up there with some of the best "affordable" DACs I've had in this system—just way, way smaller.

After some serious listening, I determined the Herus trailed the Concero HD in a few subtle ways. The chief shortcoming was instrument separation—Herus was not bad at all, but in comparison made performances seem a little homogeneous. There wasn't as much separation, making it more difficult to pick out the electric bass of Steve Swallow as compared to the acoustic bass played by Eddie Gomez on the XRCD release of "Unity" by Ernie Watts. It also felt slightly less dynamic and impactful, which mainly caught my attention with spirited drumming such as that of Simon Phillips on Hiromi's album "Voice". Again, the little Herus acquitted itself extremely well for such a compact device, and I only noticed shortcomings when compared directly to the larger and more expensive Concero HD.

I grabbed the little Herus—if only all review gear was this easy to manage—and moved it into the headphone system for some further testing. Using a MacBook Pro running Audirvana, I connected the Herus to the Icon Audio HP8 mkII tube amp and used it to drive an Audeze LCD-2 or a beyerdynamic T1. Again, very little (no pun intended!) to complain about. The LCD-2 (not the latest revision) was suitably relaxed and fun, with the smooth, pipe-and-slippers presentation I've come to love. And the T1 was snappy, quick, resolving, with the HP8 taking some (but not all) of the edge off the top end. This is a particularly difficult test in my experience—I've had smoother DACs which mask the T1's harshness but also take away too much detail, and I've had sharper, more energetic DACs which completely blow it out of proportion. The Herus managed to walk a fine line between the two, resulting in a solid basis to which I could add some coloration if needed through my choice of amplification.

Having established the quality of Herus as a DAC, I set out to explore its capabilities as an all-in-one device. Long story short, the Herus makes for a great headphone amp as well—with some limitations. I was thoroughly satisfied with its performance using relatively easy to drive headphones from Grado, Audio Technica, V-Moda, and even the HiFiMAN HE-400 planar magnetics. While lacking a bit of bass impact and overall refinement compared to the Concero HP, the Herus remains very credible sounding—low-level detail retrieval is particularly good, as is tonal accuracy. Given a headphone which isn't overly difficult to drive, the Herus may be all the amp you'd ever need.

On the flip side, the Herus is somewhat less capable when dealing with a more challenging headphone. The HiFiMAN HE-500 gives a serviceable performance but wouldn't be my first choice. Volume capability is not really the issue, but rather "drive" just feels a little thin, a little bland, nullifying some of the best aspects of the headphone. The HE-6 is, unsurprisingly, completely off the table—not enough juice to get it even moderately loud with my favorite jazz recordings. Same deal with the Thunderpants, although the Alpha Dogs surprised me by sounding reasonably satisfying. In short, I'd stay away from the more challenging planar headphones if I intended the Herus to be my only device. Which doesn't seem unreasonable at all given the intent of the device.

An interesting experiment involved going from the Sennheiser HD598 to the HD650 to the HD800—I was able to hear the progression of the Herus as it ranged from excellent performer to being somewhat out of its element. The HD598 was a brilliant pairing, reminding me that Sennheiser can still make a respectable headphone without breaking the bank. It sounded about as good as I've ever heard straight from the Herus. HD650 was mostly enjoyable but I started to hear some weaknesses peeking through....a little softness here, some lack of engagement there. If this was my main system I'd be satisfied for the moment but would probably want to add a dedicated amp somewhere down the line. Finally, switching to HD800 had the Herus starting to unravel. It was reasonably clean and detailed but also rather uninvolving, its sharpness and lack of warmth going beyond the usual HD800 character. The HD800 is slightly less sensitive than the HD650 but known to be somewhat more difficult in terms of system synergy, and that definitely played out here. Sure, driving a $1,499 headphone straight from a $350 portable DAC/amp may seem absurd...but you just know someone will want to try it anyway.

I never really expected the tiny Herus to drive every full-sized headphone with authority. So none of this is very surprising. What I was hoping for was excellent performance with my custom in-ear monitors. The elements are all there, especially the low output impedance, and in general the Herus lived up to my expectations—with one potential issue. Hiss. Yes, the dreaded hiss, which manifests itself in so many portable headphone amps, makes an appearance here as well. It's not the worst I've ever heard, and in some cases it's so quiet I only notice it in the silences between tracks. But with some IEMs it's loud enough to detract from the experience. I'd say it was present, to some degree, in most of my IEMs, and loud enough to be borderline obnoxious in roughly half of them. Some people are more sensitive to this than others so it may not be an issue for everyone. I suspect this has to do with the pressure Resonessence Labs (and other companies) must feel to make a device that powers everything under the sun. Personally I'd prefer if the Herus was silent with my IEMs, even if that meant reduced capabilities with full sized models. But that's just me.

Portable Bliss
Having established which headphones work best, I took the Herus with me on the go. I'm not usually much of a portable type of guy—I tend to listen straight from a smartphone or DAP most of the time, rather than lug a portable amp around. So I should say I mainly used the device in a "transportable" capacity. Semantics aside, the Herus was excellent for turning my iPad into a higher-end music source. Using Onkyo's HF Player allowed me to easily play hi-res and even DSD tracks without issue. There's a whole host of alternatives (FLAC Player, Golden Ear, Capriccio, Equalizer Pro, etc) but HF Player is by far the most polished, complete solution out there right now. I also used a Lenovo Windows 8 tablet and had a good experience there as well. The app selection is not as strong (I used MediaMonkey) but in the end it did everything I wanted it to do, with bonus points for micro-SD card expandability. I gotta say, as much as Microsoft has failed to make a significant dent in the tablet arena, they sure got a few things right; microSD and USB DAC capabilities seem common on every model I've tried. I'd love to see Android devices follow the same path.

Ultimately, If you do a lot of travelling and want a rig to accompany you, Herus plus compatible tablet is a fantastic solution. I've got a Chord Hugo here for review and as spectacular as that thing sounds, the little Herus seems like a more realistic choice for most people. Hugo costs over six times as much and while it does offer reference quality sound, Herus matches most of the core functionality and sounds darn good in its own right. But I suppose it's ludicrous to compare them directly so I'll quit while I'm ahead.

Final Thoughts
The diminutive Resonessence Labs Herus is an exceptional DAC and—with some caveats—a rather capable headphone amp as well. It sounds far better than I had hoped, plays everything I throw at it, works well at home and on the go. What's not to like? My only gripe is with the hiss present when using some IEMs. Resonessence Labs probably made a tactical decision to increase power at the cost of some hiss—it's not the choice I would have made, but I can see the reasoning behind it.

After auditioning many of the options in this relatively new segment, Herus stands out as one of the few I can recommend based strictly on sound quality. Most of them rely on their convenience and affordable pricing to help offset expectations. Herus offers the total package, for that it's definitely "Stuff We Like", and heartily recommended.

Resonessence Labs
863 Coronado Crescent
Kelowna, British Columbia V1W 2K3
(778) 477-5536

nnotis's picture

Thank you for pointing out this problem! Just about every one of these dongle DACs has it. You need only read through their respective threads on Head-Fi to understand why. People are obsessed with driving LCD-2s & HD800s with them. By doing so, manufacturers end up building amp components that sound poor with everything. From what I understand, even the Hugo is noisy with IEMs. But hey, I bet they sound kind of Ok with HD800s as a result. It's frustrating, since it should be possible to get reference quality sound from a mini DAC and top of the line IEMs. Lower the gain please!

John Grandberg's picture
I think "sound poor with everything" is taking it too far. The Herus, and (to a lesser extent imho) some of its competitors sound very good with the right headphones. As I said, I personally would prefer to have a silent amp section for use with IEMs. Obviously the masses demand otherwise. Makes sense, I suppose - on the high end, the full size market is probably far larger than the IEM market.
miceblue's picture

Have you had the opportunity to try Light Harmonic's Geek Out device? People in the LH forums seem to be talking about the Herus often and it would be really cool to see a highly regarded reviewer such as yourself do a comparison.

John Grandberg's picture
Tyll has a Geek though, and a bunch more, which is why I'm sending over the Herus for him to compare.
Broman's picture

"I also used a Lenovo Windows 8 tablet and had a good experience there as well. The app selection is not as strong (I used MediaMonkey)"
I don't understand this comment. If it is Windows 8 why can you not use Foobar, etc.?

John Grandberg's picture
To clarify - yes, you can use Windows 8 in "desktop" mode, and indeed you must do so initially to install the drivers. Foobar works fine but is not so fun on a tablet. I prefer MediaMonkey since the app is optimized for the touch screen and smaller display. Foobar is very flexible with customization so one could theoretically set that up to their liking, but I didn't feel like messing with it.
funambulistic's picture

MediaMonkey has a few quirks but the GUI is great on the Windows tablet.

NZtechfreak's picture

It'll work with a number of Droids via the app Ultimate USB Audio Player PRO (UAPP), I used it with my Note 3 and it worked fine. UAPP has its own USB drivers and bypasses Android audio handling allowing for greater than 16-bit audio (should the user want that) and much increased DAC compatibility. It's more or less local playback only, but then with the availability of 128gb microSD cards that isn't too bad (and in fact I'm using a 256gb full-sized SD card with my Note 3 via an adapter).

John Grandberg's picture
I consider USB Audio Player Pro a sort of work in progress. At first it was a mere novelty, and later it became somewhat usable. It's still got a long way to go compared to some of the top playback apps though. Still, I appreciate the project, and I check back in every few months to monitor their progress.
NZtechfreak's picture

Definitely a work in progress, but a serviceable enough player for those of us who care most about fidelity and using DACs that otherwise might not work with our phones. I use it on the go with my Dragonfly 1.2, whose form factor cannot be beat for this application being basically an inline DAC and amp - it requires UAPP however in order to use the amps volume control.

John Grandberg's picture
I can see it becoming a killer app in the next year or two. I just wish Android had this stuff built in from the get go.