NuForce HA-200...Dual Mono Madness!
I covered the bulk of the NuForce Home Series gear last year and found it well done across the board. A dedicated speaker amp, headphone amp with preamp capabilities, a DAC, and the "digital integrated" DDA-100; all sharing the same design theme and all sounding pretty darn good. With most of their bases covered, the lineup remained fairly consistent without any major new releasesuntil now. I had anticipated maybe a new DAC with XLR outputs and DSD capability (DSD being all the rage these days) or perhaps a beefed up version of the popular DDA-100 with increased power. Instead we get...another headphone amp? Huh? I sure didn't see that coming.
So, the question is: Why add another headphone amp to the lineup? The HAP-100 ($595) remains a current model, one that I still enjoy quite a bit. The release of the new HA-200, which at $349 is a more affordable device and ostensibly a step down (if judged purely on price), seemed puzzling. I figured maybe NuForce got complaints from people wanting a pure headphone amp without the preamp stuff on board. Dropping the multiple inputs and motorized volume pot seems a reasonable way to lower the price, but it's still not very exciting. And if that's all it was, I probably wouldn't bother writing about it. No, the HA-200 is something different all together.
First things firstthe HA-200 uses what initially appears to be the same enclosure as the other Home Series models. Measuring about 9 inches deep, 8.5 inches wide, and 2 inches tall, it's actually a totally new enclosure with a very similar theme. Choosing the silver option nets a silver faceplate on a black body, while the other Home Series component are silver all the way around. I suppose it's a minor detail, but a DAC-80 plus HA-200 rig in silver would not be a complete match. Am I being picky here? Maybe, but it feels like a slight oversight. Unless of course NuForce is now using this enclosure with all their models, which is certainly a possibility.
Next up, external stuff. The HA-200 is singular in purpose, meaning just a lone set of RCA inputs rather than 4 inputs plus a preamp output like the HAP-100. But wait a minute.... what's that weird plastic cover on the front panel, next to the 1/4" headphone jack? And why is there a lone 3-pin XLR input on the back? That doesn't make any sense, does it?
Allow me to explain: The HA-200 is perfectly happy being used as a straight forward headphone amp. Connect a source via RCA input, plug in your headphones, and go to town. However, NuForce also allows the user to run a pair of them in a dual mono configuration. Yepyou've seen monoblock amps in speaker rigs, and recently in a few (rather expensive) headphone amps from Questyle and Woo Audio, but NuForce brings the concept to a decidedly more affordable end of the market. NuForce claims this pays dividends in terms of voltage swing, current delivery, slew rate, and crosstalk. It also allows the user to incrementally build up the system rather than shelling out full price right out of the gate. I'm a big fan of incremental upgrades so that aspect intrigues me, assuming there's really a gain to be hadwe'll find out soon enough.
To access dual mono mode, the HA-200 pair requires a source with XLR outputs and a balanced headphone terminated with dual 3-pin XLR. If you're like me and prefer the 4-pin XLR style of termination, you'll need an adapter. The HA-200 combo will automatically switch to monoblock mode when connected this way. That plastic cover thing on the front panel? It swivels up and out of the way, revealing the XLR jack. I'm not sure this would have been my first choice for aesthetic reasons but I guess it does the job well enough, and maybe adds a bit of intrigue to the otherwise straight-forward appearance.
The obvious temptation here is to stack one amp on top of the othernot sure I recommend that as they get pretty darn hot after just a short period of being powered on. I confess that I did try stacking mine for a while but it made me slightly nervous about long term reliability, so I soon gave it up.
All that heat comes from the constant current design. The HA-200 output stage is based around an opamp/MOSFET combo heavily biased into Class A. You can read all about the design philosophy here. NuForce wisely placed significant ventilation on top and bottom of the case, so the amount of heat being radiated is probably a bit deceptive compared to amps using sealed enclosures. Still, it can be a little worrisomeNuForce's own STA-100 amp, driving 4 Ohm speakers at nearly 200 Watts per channel peak, still doesn't get this hot. Thankfully there's a 2 year warranty in place to help alleviate any concerns.
With two units in monoblock mode, volume control must be independently adjusted on each amp. Anyone who's used a HeadAmp KGSS or a HeadRoom Blockhead knows the drill. Level matching between channels is a minor nuisance for sure, but still workable, and can be eliminated altogether by using a DAC with volume control. More and more DACs these days feature high quality implementations which are able to cut a fair bit of volume before any resolution is lost. I simply max both volume knobs on the amps and run the whole shebang from my DACfortunately, the HA-200 has low enough gain (+10dB) that massive attenuation is not needed.
The low gain is surprising and rather welcome indeed. Lots of new amps seem to have more gain than I'd ever need, making precision volume adjustment kinda tricky. I'm at a loss to explain why that's done so oftenmaybe it's a race to see who can make HiFiMAN's massively inefficient HE-6 sound the loudest? Whatever the case, it's less of a big deal in an expensive amp with a correspondingly high quality potentiometer. In an affordable design the cheaper pot is likely to be a more significant bottleneck, so running at as close to wide open as possible can only be a good thing. The HA-200 omits the switched-resistor ladder network found in its HAP-100 sibling so the low gain probably is beneficial in this case.
Now, let's see how the amp actually performs...