Miniwatt n4 USB DAC-Headphone Amplifier

December 2013

Miniwatt n4Hong Kong-based Miniwatt burst onto the hi-fi scene in 2009 with a tiny integrated tube amplifier that produced a mere 2.5Wpc -- hence the company’s name. The next year brought a slightly more powerful (3.5W) model, the n3, which still had a footprint about the size of a CD jewel case. While some might scoff at such low power ratings, a few watts are all that are needed to drive a desktop audio system with speakers of moderate sensitivity. Of course, an amplifier requires a source, and if you’re focusing on a desktop system, a USB DAC is the obvious choice.

The Miniwatt n4 ($348 USD) is a 32-bit/192kHz-capable, asynchronous USB DAC with both a 1/8” headphone jack and a stereo line-level output on RCAs. It also includes a coaxial digital output, which allows it to be used as a USB-to-S/PDIF converter. Buttons on the front panel affect both the line out and headphone volumes, and plugging in a pair of headphones mutes the line output -- as it should.

The n4 measures a compact 2.9”W x 0.8”H x 4.5”D (74 x 20 x 115mm). It’s constructed of aluminum with a silver powder coating on the front and rear panels, and a hand-stitched leather wrap for the body. The combination of silver and leather reminds me of a classic camera and lends the n4 an air of sophistication -- or at least differentiation in the crowded USB DAC marketplace. Digital-to-analog conversion is by way of the well-respected Burr-Brown PCM1795 chip, followed by an LM4562 low-noise, low-distortion audio op-amp at the analog filter and driver stage.

The n4 is plug-and-play for Mac and Linux users. As usual, to accommodate sample rates above 96kHz, Windows users need to install a driver that can be downloaded from the Miniwatt support page. The manual gives instructions for selecting the default bit depth (16, 20, or 24) and sample rate (44.1, 48, 96, or 192kHz). If choosing this method of operation, all music will be converted to these default values. Alternatively, one can select the WASAPI Push mode from one’s media player of choice -- Event Style doesn’t appear to be supported. This approach should avoid the global audio mixer, and maintain your music’s original bit depth and sample rate. The n4’s CM6631 USB receiver chip is specified to support all major sample rates from 44.1 to 192kHz, including 88.2 and 176.4kHz. I had no trouble with 88.2kHz files, but my 176.4kHz tracks returned an error. Apparently, the n4 will pass all sample rates through its S/PDIF output.

Miniwatt n4

The specifications indicate that the n4’s digital volume control operates through a range of 0-120dB in 0.5dB steps. While that facility exists on the PCM1795 DAC chip, I verified with Miniwatt that the volume buttons simply control the software volume. This means that if you want to use the Miniwatt’s physical volume buttons, you must select the n4 as your primary output device. Otherwise, you can control volume within your media player.

With a maximum output level of 1.8V RMS, the Miniwatt’s RCA outs are well suited for connection to a preamplifier, or directly to powered speakers. The headphone jack is specced to deliver 100mW into a 32-ohm load, which is more than enough for the vast majority of moderate-impedance ’phones.

Sound

Most of the time I spent listening to the Miniwatt n4 was through headphones. It had no trouble driving the Alpha Design Labs H118 and PSB M4U 2 ’phones (in the latter’s passive mode) to satisfying levels, with plenty of headroom for macrodynamic swings. It even did a creditable job with the obstinate HiFiMan HE-500 planar-magnetic headphones -- though these really need a more brutish amplifier to deliver their ultimate performance. On the small scale, the n4 was quiet enough for use with in-ear monitors such as my Etymotic ER-4Ps, but it could be difficult to dial in just the right volume. A tap on the physical buttons increased the system volume by 4-8%, so I used the slider on the computer instead.

Each of the last few DACs I’ve reviewed has had its own distinctive sonic signature. Nothing about the n4, however, immediately drew my attention. That’s not at all a bad thing -- neutrality is what many audiophiles seek. However, to say that a DAC is “neutral” is to say only that it is free of overt colorations, not that it is lacking in individual character.

The n4’s top end was sufficiently extended to give a nice shimmer to the cymbals on Paquito d’Rivera’s Portraits of Cuba (24-bit/88.2kHz FLAC, Chesky/HDtracks), and a good accounting of the horn line’s upper harmonics, but was sufficiently forgiving not to exacerbate the hard edges of the terrible 1990 digital transfer of Sade’s Diamond Life (16/44.1 FLAC from CD, Portrait RK 39581). “Rolling in the Deep,” from Adele’s 21 (16/44.1 FLAC, XL Records), sounded a little raw, but no more so than through other mostly neutral DACs. Compression artifacts in the few MP3s that I played through the Miniwatt were audible, yet tolerable.

Miniwatt n4

My one minor criticism was of a slightly too metallic quality in the sound of massed strings -- even with good recordings, such as Mahler’s Symphony No.5, performed by the London Symphony Orchestra under Valery Gergiev (24/48 FLAC, Society of Sound). The n4 also made the opening trumpet call in the title track of Billie Holiday’s Lady Sings the Blues (24/96 FLAC, Verve/HDtracks) sound a little more brash than it ought to. Pairing the n4 with somewhat warm ancillaries -- perhaps Miniwatt’s own n3 tube amplifier -- might mitigate this concern.

I have little to say about the n4’s midrange; voices and instruments retained their integrity and were well integrated into the overall musical fabric. At the bottom, the Miniwatt’s bass was well extended and free of excess bloat. Ray Brown’s double bass was taut and tuneful on the Oscar Peterson Trio’s Night Train (24/96 FLAC, Verve/HDtracks), and Bernard Purdie’s kick-drum attacks on Bucky Pizzarelli’s Swing Live (24/88.2 FLAC, Chesky/HDtracks) were reasonably firm and decisive. Although I neglected to measure the Miniwatt before shipping it back, the n4 controlled all of the headphones I used with it, which suggests that it has a suitably low output impedance. Using the line-out to connect the n4 to my main system, I found its bass less authoritative than that of my usual reference components, but very much in line with that of other USB-powered DACs.

Good channel separation meant a fairly spacious image with appropriate headphones, and a soundstage that extended from edge to edge of my loudspeaker setup. That soundstage began a little behind the speaker plane, but was somewhat lacking in depth. Images on that stage were firmly placed, but the overall focus was a little soft. Given the uses to which the n4 is likely to be put, these shortcomings should be of relatively little concern.

Conclusions

A great many USB DACs are available at the Miniwatt n4’s price. The provisions of headphone, line, and digital outputs, along with physical buttons for volume control, make it one of the more fully featured examples. Though my audiophile wish list includes volume adjustment done on the chip, not by the computer, the difference isn’t a deal breaker. A neutral sound from top to bottom will work well with any style of music, and the n4’s slightly forgiving top end will cause offense to none. All wrapped up in an attractive package, the Miniwatt n4 is well worth a look -- and, of course, a listen.

. . . S. Andrea Sundaram
andreas@soundstagenetwork.com

Associated Equipment

  • Digital sources -- Grace Design m902 DAC-headphone amplifier, Ayre Acoustics C-5xeMP CD player
  • Headphones -- HiFiMan HE-500, PSB M4U 2, ADL H118, Etymotic Research ER-4P
  • Amplifier -- Graaf GM-50
  • Speakers -- Esoteric MG-10, REL Serie R 328 subwoofer
  • Computer -- custom Windows Vista laptop running foobar2000
  • Interconnects -- Nordost Red Dawn LS, DH Labs Revelation, QED Silver Spiral
  • Speaker cables -- DH Labs Q-10
  • Power conditioner -- Equi=Tech Son of Q

Miniwatt n4 USB DAC-Headphone Amplifier
Price: $348 USD.
Warranty: One year parts and labor.

Miniwatt
Phone: +852 2575-6282

E-mail: sales@miniwatt.com.hk
Website: www.miniwatt.com.hk

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