When I first laid eyes on the Aurender Flow, I didn’t get it. Taken from its form-fitting leather case it looked like another portable player, albeit big and sorta on the heavy side. It also looked 90s-ish with a big ol’ center knob, a wiggly curve to its chassis resembling a logo for a hydro-spa, and one lone single-ended headphone output. Paging Forrest Gump: We got your portable player, right here. But I was completely wrong.
First, let me make one thing perfectly clear, the Aurender Flow is not a portable player. It is, in fact, a DAC and headphone amplifier capable of being used as a preamplifier and external drive (if a drive is installed in it), that makes it ideally suited for nearfield high-performance desktop use. That large knob I mocked earlier…well, its size and feel make it one of the most accommodating volume knobs I’ve ever had the occasion to fondle while hunting for that ideal SPL.
With its footprint measuring only 5½" by 3½" by 1", Aurender packs a lot of technology into the Flow’s one-pound chassis. The DAC uses an XMOS USB interface and Sabre ESS9018K2M chips, and has its own internal 4450mAh battery power supply. The Flow can handle any digital data stream up to 384/32 PCM and 128x DSD via USB and 192/24 PCM via its TosLink input. Although the Flow has only a single-ended ¼" ’phone-jack output, it can be configured in several ways. It can be variable output in 0.5dB increments up to 2 volts or you can configure the Flow for fixed output at either 2 or 5 volts. No, that was not a typo—5 volts. Output impedance is only 0.06 ohms.
The first time I saw the Flow I was confused by its m-SATA drive capability. You can add a drive to the Flow, and most people would assume it is for storing music to be played on it. They would be correct, but unlike a portable player where you could access the drive on the go, the Flow’s drive can only be used when it is connected to a computer. But using an Apple camera connection cable, one can also access the contents of an iPad or iPhone.
In function, this is similar to the Auralic 2000 DAC/headphone stand that I reviewed in Issue 246. It, too, had provisions for tethering a drive that could only be accessed while the Auralic was connected to a computer. The difference is that the Flow holds the drive internally while the Auralic uses external drives.
The Flow is the first USB DAC I’ve seen that is USB 3.0-compatible. If your computer only supports USB 2.0, no worries, the Flow has provisions within its menu for several different “host modes” optimized for various computer systems. The options include USB2, USB3, Mac, IOS, and Android.
The Flow also has user-selectable digital filters. For PCM it has, by default, a PCM1 filter (which is a slow roll-off, in-band filter), and a PCM2 (which is a minimum-phase PCM filter). DSD users have the option of moving the DSD cut-off filter from the default, DSD at 47.7kHz, to 50, 60, or even 70kHz. There are three charging options: CHG+ is constant charging mode; CHG- turns off the charger; and CHGA- configures the Flow for automatic charging whenever music is not playing.