The simplistic design of the Dr. DAC Nano doesn’t give you any method of volume control, and when you want to use it as a headphone amplifier, you need to control the volume directly from your computer. With the Mac, this can be done either through the Itunes or the Mac volume control (The Nano responds to both). It works pretty well actually, as adjusting the sound through the computer is quite convenient. It’s also good in the way that there is no concern about channel imbalances that plague analog volume controls at very low volume levels (something that is often an issue with IEMs). I actually think that the Nuforce uDAC would sound better if they take the same approach and discard the volume control, since the analog out on the uDAC, both RCA and headphone amp, is controlled by the volume pot, and to a certain point, volume pots (especially small one) degrade signal purity.
Although jitter cops would totally disapprove controlling the volume through the OS mixer, as it adds jitter through the software processing, I think the effect in real life is still lesser than the analog signal degradation through a conventional pot.
With the AD8397 opamp, power level at the analog out is very loud. With the Itunes volume on maximum, and roughly 65% on the Mac volume level, the Nano drives my HD800 very loud with decent impact as well. Compared to the uDAC, the headphone out section of the uDAC is still slightly more powerful than the Dr. DAC Nano, where 1 O’clock on the uDAC is just close to the maximum loudness level that I can handle with the HD800. The upfront presentation of the uDAC also sounds better when comparing the headphone out, as the detail on the music is easily more audible.
I was curious to test if the Nano indeed is capable of 24/96 resolutions, and so I hooked up the Nano through the USB to the Macpro, then out with a toslink optical cable to the Grace m902. ESI has supplied a nice adaptor so that you can use the common Toslink cable.
I went to the Mac midi settings and set the output to 24/96.
When everything is set up correctly, the 96 kHz light on the Grace would light up, confirming that the Nano is indeed transferring music data at 24/96. I was not able to test for bit perfect though, as the Grace’s DAC reclocks all incoming digital data to its own internal clock using the proprietary s-Lock. Playing 24/96 files from Reference Recordings is a joy, as the 24 bit really sounds smoother and less digital-choppy on extreme passages when compared to 16 bit tracks. Not bad for $99!
Okay, seeing that very little music is available today that’s in 24 bit, the real comparison, at least in this price bracket is still on the 16/48 land. Between the $99 uDAC and the Dr. DAC Nano, the choice is not an easy one, as the Dr. DAC Nano has a better sounding DAC, but the uDAC has a more powerful headphone out (although that power may not be needed). The difference in the DAC performance between the uDAC and the Nano is very close, and if you prefer a one box DAC+Amp solution, the uDAC might be the better choice, whereas if you’ve already own a portable amp, the Dr. DAC Nano makes a more ideal pairing. Compared to the Styleaudio UD-1, the Dr. DAC Nano’s DAC still fall short, but it does make up the loss with a very usable headphone out (that the UD-1 doesn’t have), and it also come in a much smaller package that would go well with anyone using a small netbook laptop or something fancy like the Macbook Air.
System used for review:
Headphones: Sennheiser HD800 with APureSound Balanced Cable, Unique Melody Mage 4 drivers custom IEM
Amplifier: Balanced TPA6120 Amplifier, built in amps of the respective DAC units
Source: ESI Audiotrak Dr. DAC Nano, Nuforce uDAC, Styleaudio UD-1