NuForce "Home Series" Quality Compact Audio Gear
Fremont, CA based NuForce has been around for a while. They were traditionally known for their higher-end digital amplification, preamps, and DACs. More recently, they are also well-known for their low priced series of smaller components. When I heard about NuForce launching a new line called "Home Series", I became intriguedbridging the large gap between models like the $7600 Reference 18 and the $189 Icon seems a wise choice.
Nuforce seems to have their gear divided into three categories, and it can get a little confusing. Catalog links on the left side of this page should help. It shows the "Hi-End" line encompassing preamps, amplifiers (stereo, monoblock, and integrated), and the Reference 9 DAC. I've been calling this stuff the "Reference" line but I now realize that isn't entirely accurate, only a few of them actually use that specific title. In any case, these models are priced in the thousands rather than hundreds, and you'll recognize them right away by their nicely sculptured front panels. Then there's the "Consumer" line which features the "Icon" branded amps and DACs, the uDAC2, the Cube compact speaker, and a few headphones. This line is affordable, with many items being under $200 and its most expensive member being the Icon HDP at $449. So you can see the discrepancy between it and the Hi-End line.
To fill that space, NuForce recently launched the "Home" series. Like the Icon series, the Home products use similar enclosures with minor variation as needed for each individual model. And I personally think they look quite sharp, in a sort of modern, minimalist wayIkea could use these in their catalog and it wouldn't feel out of place. Pricing tends to be comfortably under $1,000 with the sole exception of the DAC-100 which is $1,095. I reviewed (and enjoyed!) that device at HeadFi not long ago, and frequently used it as a source to evaluate these other Home series models.
DDA-100 Integrated Amp ($549)
Kicking things of for the home series is the DDA-100 ($549) which is an integrated amplifier with a twist. Like every member of the Home series, the DDA-100 (available in black or silver) is 9 inches wide, 8.5 inches deep, and 2 inches highsmall enough to fit on all but the most cluttered desktop. Despite the small stature, Nuforce was able to cram a good amount of connectivity into the device. It features dual Toslink inputs, a coaxial input, and of course USB. Astute readers will notice the lack of any type of analog input. That's deliberatethe "twist" I mentioned is the DDA-100 functioning entirely in the digital domain. Also, there just isn't enough room for legacy inputsI certainly didn't miss them. Also on board is an optical output, meaning the DDA-100 can function as a USB to SPDIF converter, as well as integrating into more complex systems.
So what exactly does a "completely digital" integrated device look like? It's a tricky thing because actual sound, as it travels through the air, is inherently analog. Yet the DDA-100 does not use the typical digital to analog conversion we are familiar with. Instead, digital inputs feed PCM signals straight to the Class D amplification section with no D/A conversion step in between. Class D is also known as PWM or Pulse-Width Modulation. Some people will immediately balk at that description and assume it has no place in an "audiophile" device. Not so fast. Class D amplification spans the range from cheap solutions used to power the crappy speakers in your TV, all the way up to authentically high-end gear like the $5,999 NAD M2 and the similarly priced Bel Canto Ref1000M monoblocks. Assuming all Class D amps perform identically is just plain misguided. It's like making that same assumption about Class A or AB ampsit just isn't true.
The "D" in Class D does not stand for Digital and as amp guru Nelson Pass once said, "PWM is definitely analog". Yes, in simple terms the PWM process involves a binary status for the switch modes of the output devices1 or 0, on or offbut is actually defined by the duration between switch changes, and as such is practically limitless in intermediate values. That sure sounds analog doesn't it? On the input side, the DDA-100 actually resembles a DAC more than a traditional integrated amp. An AKM digital receiver and NuForce branded USB section accept incoming signals and route them to dual Infineon SAB2403 chips (1 per channel). These are highly integrated devices featuring onboard DSP, sample rate conversion, and digital filtering among other things. Volume control is also handled in the digital domain, accessed from the freely spinning front panel knob or the compact remote. That same multi-function knob pushes to cycle through the 4 inputs (hold it down to go in or out of standby mode), and two pleasingly-dim displays show volume level and active input. The whole thing sounds more complex than it really isin actual use, the DDA-100 is quite simple and effective.
As far as specs, NuForce rates the device at 50-Watts RMS into 8 ohms and 75-Watts RMS into 4 ohms, with a far higher peak rating. Inputs are limited to 96kHz, a deliberate choice on the USB side to keep things Plug and Play across all platforms. I inquired about potentially improved jitter by using an asynchronous USB interface and NuForce advised that due to their re-clocking process, all inputs measure the same in terms of jitter. So there would be no theoretical benefit to improving the USB implementation in this particular device. The only thing I can really complain about is the sample rate ceiling. I can actually play my 24-bit/176.4kHz Reference Recordings HRx tracks through the coaxial input but it doesn't like 24-bit/192kHz files. And the other two inputs top out at 96kHz as advertised. A minor issue at worst.
My initial task for the DDA-100 was in a desktop system. I used it in a deceptively low key setup to drive the wonderfully transparent Salk WOW1 monitorsjust add computer, no messing about with other boxes or interconnect cables. All I needed was a USB cable and speaker cables (obviously). For the latter I used Charleston Cable Company Auric cables because they were so much more flexible and compact than any other cables I had on handa desktop system is no place for garden hose audiophile speaker cables. Thankfully the DDA-100 is low profile enough to fit any number of spaces on a desktop. Try that with a full size integrated amp.
My first impression of the DDA-100 was in comparison to the gear formerly occupying that spota Resonessence Labs Concero DAC and a Consonance M10S tube integrated. The DAC is an extra variable which simply couldn't be avoided. Nonetheless, the Concero/Consonance setup is a very satisfying pair which I'd say competes well at its ~$1700 price. The DDA-100 had similar levels of transparency and openness, and in fact was surprisingly similar in overall character considering their differences in topology. Keeping in mind the price difference involved, this already speaks highly of the NuForce unit. The DDA-100 exhibited none of the bright, edgy, thin sound that some people erroneously attribute to all Class D amps. What it did have was an unflinching level of claritywhere the Consonance made everything flow smoothly and was relatively forgiving, the DDA-100 had a more direct presentation, for better or worse. Great recordings such as the previously mentioned Reference Recordings HRx tracks sounded palpably real from top to bottom. Even 16-bit/44.1kHz material such as the MFSL edition of Frank Sinatra's Nice 'N' Easy or Kiss Me Hello by Kristin Andreassen sounded exceptionally detailed, with a rich full-bodied tone that I normally associate with larger (and more expensive) separate components. The flip side of this accuracy was mediocre recordings being laid bare. Praise & Blame by Tom Jones and Dancing in the Dark by Tierney Sutton both have significant flaws, and in the DDA-100 system they border on unlistenable. The more forgiving Consonance amp makes them somewhat more palatable, especially with regards to the sibilance in Sutton's voice. Lipstick on a pig? Most definitely. I can see how the DDA-100 would be less appealing depending on one's musical preferences, but given reasonably good material I'd say it really punches above its weight class.
Next I did something which would cause most compact desktop-friendly amplifiers to run for coverI added the DDA-100 into my 2-channel setup. But this is only fair considering NuForce bills it as a straight integrated amp and never specifically mentions desktop use. The speakers involved were the Sjofn HiFi (the clue) monitors which are 87dB efficient. The room is what I'd call midsized and the usual setup is based around a Parasound Halo A23, which is significantly more powerful than the little DDA-100. The two devices couldn't be more different. The Parasound is a beefy full-sized component weighing in at nearly 30 pounds, packing a linear power supply and a dozen bipolar output transistors. Comparatively, the NuForce looks like a toy. And yet in terms of sound the two are surprisingly close. In fact, the choice of preamp driving the Parasound seems the key factor. Using the AURALiC Taurus ($1799) brings the larger amp up to roughly the same high level of transparency as the DDA-100, albeit with more drive and dynamics, and at a considerably higher price. But using a more affordable device such as the Grant Fidelity TubeDAC-11 ($350) or Matrix M-Stage ($300) as preamp, the DDA-100 takes a clear leadbetter transients, more fleshed out midrange, less grain. This tells me the "all digital" approach does indeed reduce bottlenecks. It only makes sense, reducing the number of analog gain stages in an affordable multi-function device seems completely logical to me.
One key strength that the DDA-100 had was the ability to render a believably three-dimensional sound field. This is probably related to the extremely black background and clear-yet-controlled top end detail. Whatever the case, the little NuForce box presented a deep, highly-resolved soundstage that extended well beyond the physical limits of the speaker enclosures. The Taurus/Parasound combo had more authority and could be more convincing with very loud orchestral works, but never quite matched the little NuForce when it came to delicate imaging. Swapping out the AURALiC for my Analog Design Labs Svetlana 2 (a $1500 single-ended triode unit) allowed the Parasound to match and maybe even exceed the spaciousness of the NuForce at the expense of some dynamics. In the end it seems the DDA-100 is a good compromise between the Svetlana and Taurus preamps as heard through the Parasound amp, capturing many (but not all) of their strengths but in a smaller and more affordable package. The caveat would be volume limitations, in a room larger than mine, or with speakers less sensitive than mine, I'd definitely start to worry about maximum volume capabilities, especially with quiet jazz recordings.
This impressive soundstage puzzled me as I recall an early review complaining about a flat, two dimensional presentation. Was it just my particular room or speakers that mated well with the device? Or was something else amiss? Then I noticed the interior of my unit looking very different from pictures posted in that early review. I discussed this with a NuForce engineer and sure enough, my unit is a "V2" model with significant changes. It turns out the V1 power supply was an off-the-shelf design that didn't perform quite up to expectations, despite its impressive looking, confidence inspiring external shielding. The new power supply is custom made for this specific project, using a better topology and improved components. A side effect was the radiation issue being dealt with at the source, meaning shielding was no longer necessary. In addition, the new design had better regulation so the large coupling cap seen in the original was no longer required. These significant changes could explain why I hear things very differently than that initial review.
The DDA-100 is paradoxically versatile and limited. It delivers huge performance from a small enclosure, and can replace multiple larger and more expensive devices in a system with little to no penalty in sound quality. In that sense it is definitely versatile. Yet it's limited in the context of its interactions with the other NuForce Home series models. The only time I see this being an issue is trying to work a headphone into a DDA-100 based system. That limitation, as well as the obvious need to keep expectations in check regarding room size, max volume, and speaker sensitivity, appear to be the only compromises in an otherwise exceptional offering. Whether on my desktop or in my living room, the DDA-100 never failed to impress, and I can confidently recommend it.