In the short time it’s been around, Aurender has already garnered a reputation for making excellent-sounding gear. The Flow should enhance its already sterling character. I used a wide variety of headphones with it and couldn’t find a mismatch. Unlike some headphone amplifiers that favor a particular set of headphones or type of ’phone, the Flow was very much an equal opportunity amplifier; everything I threw at it worked fine and sounded good. Also, the Flow allowed each headphone to produce its own unique sound signature. Grado RS1s still presented a different soundstage and imaging characteristics than Mr. Speaker’s Alpha Dogs.
Flow users have several PCM digital filter options that I mentioned earlier. Listening to Sia’s “Chandelier” off Tidal, I liked the PCM2 filter better than the PCM1 default. PCM2 produced better decipherability of her phrase “can’t feel anything” and more precise imaging on the background singers located hard left and hard right. Also in this mode, the intentionally added distortion bed was a hair less aggressive. In the past I’ve found that many PCM filters are more software than hardware dependent, and this was true with the Flow. Some music will benefit more from one PCM filter setting than another, so it’s not a question of which filter is overall the “best,” but rather, which one suits the music better. Too bad the Flow can’t remember and employ whichever filter setting you find is preferable for a particular track, but as of now you still must change the filter settings manually via the menu.
I also used the Flow as a DAC/preamp by feeding its output to the analog input of the NuForce DAC-10H. Although it required using a ¼" headphone-to-female RCA adapter and then a 1 meter length of interconnect (I recommend something flexible such as the Kimber KCAG for this task), the setup worked nicely. I found the Flow’s noise levels were lowest when I used the 2V fixed-output mode coupled with no battery charging. I used the NuForce ST-10 power amplifier tethered to a pair of Audience 1+1 speakers in my desktop system for these listening sessions. I also had a Velodyne DD10+ subwoofer tethered to the DAC-10H. I was impressed by how close the sound quality of the Flow was to the NuForce DAC-10H. Once levels were matched—which was pretty easy with the DAC-10H’s numbered volume settings—the DAC-10H had a slightly wider soundstage, but the Flow’s soundstage was deeper. The DAC-10H also had better low-level detail due to its somewhat quieter base noise level, but the Flow matched the DAC-10H’s dynamics and pace.
I also compared the Flow with the Oppo HA-1, once more using the Oppo’s analog inputs so I could compare the two in a matched-level A/B test. Again it was a close call with the Flow having better dimensionality and upper-midrange energy and the HA-1 having more relaxed transient response. The Flow produced a more three-dimensional soundstage, but the HA-1 produced better lateral delineation and separation between instruments in the soundstage.
Neither the Oppo HA-1 nor the NuForce DAC-10H could successfully handle as wide a range of different headphones as the Flow. Even with its different gain ranges, the NuForce DAC-10H could not go from high sensitivity to low with the same equanimity as the Flow. With the DAC-10H, you have to hunt and peck for the best combination of gain and volume; with the Flow, you merely turn the volume knob to the right point. And while both the Oppo HA-1 and the NuForce DAC-10H offer far more flexibility in input and output options, if your primary use will be with headphones and not as a preamplifier for a speaker-based system, the Flow’s feature set and sound make it a better option than the other two.
I’ve heard there are some audiophiles who like an uncluttered desk. For someone who wants great sound, smooth ergonomics, and a compact footprint, the Aurender Flow offers an elegant solution for headphone and nearfield listening. Put a large mSATA hard drive in it and you have a clever rig for a traveling audiophile. Although the Flow will work in portable applications, in my view its one-pound weight and form factor make it more suitable for desktop service. Also, The Flow could easily find a place with music professionals, carrying it from studio to studio to ensure monitoring consistency.
Never before have audiophiles had so many fine options for DAC/preamps in the $1000 to $1500 range. I’ve mentioned several with which I’m familiar during this review. But the Flow’s physical dimensions and its ability to drive everything I could throw at it headphone-wise make it special. Yes, my first impression of the Flow was wrong, but after giving it a chance to strut its stuff, I have to admit that it has become my current go-to headphone listening rig. If headphone listening from a computer source is your thing, you need to hear the Flow because it was made for you.
SPECS & PRICING
Sample rates: Up to 192kHz via SPDIF; up to 384kHz, DSD128x via USB
Compatible bit depths: 16–24 (SPDIF), 16–32 (USB)
Internal storage: Up to 1TB total via mSATA bus
Output impedance: 0.06 ohm
Output power (0.1 percent THD): 43mW/600 ohms, 87mW/300 ohms, 384mW/56 ohms, 570mW/32 ohms
THD (1kHz, 5.1V RMS output): 0.0002 percent
Dynamic range: 122dB
Damping factor: >130
Power supply: 4450mAh Li-ion rechargeable battery
Dimensions: 3.1" x 5.4" x 1.1"
Weight: 1 lb.
Price: $1295 without mSATA drive