Shure's scantily-titled X2U is a USB mic preamp, and though there have been plenty of such products on the market recently, the X2U has a more sophisticated feature set than many of its direct competitors.
The X2U operates at 16-bit resolution, at sample rates up to 48kHz, and manages a low noise-floor of -78dBFS with the mic gain turned up. It can provide 48V phantom power, and headphone monitoring is built in, available via a 3.5mm stereo mini-jack — so there's no need to mess around with aggregate drivers. There's even basic green/yellow/red LED record-level metering, via a multi-colour LED: yellow equates to a healthy -12dB record level, red indicates clipping, and green signifies that the input signal is above -30dB but below -12dB. Three thumb-wheel pots that are recessed into the side of the X2U allow adjustment of mic gain (over a 40dB range), phones volume, and monitor. The last control adjusts the mix heard in the headphones of your computer's audio output and the mic input, which enables you to do basic zero-latency source monitoring.
The build quality is very reassuring. The all-metal body includes a flat base with a rubbery coating, and two slots that could be used to attach it to a mic stand, using the two Velcro straps that come wrapped around the included USB cable. Power comes from the USB port, and a green LED shows that the unit is powered up. If the phantom-power switch is pressed, a blue LED also comes on. The female XLR on the end of the X2U may be connected to a conventional mic cable, or could be plugged directly into a mic.
The X2U works with Windows or Mac, and no dedicated drivers are needed, because the X2U is recognised as a standard USB class-compliant device. The first thing I noticed when testing the device is that the headphone monitor quality is extremely good, but of course this product's raison d'être is recording. My tests were done leaving around 6dB of headroom when recording: although 24-bit recording allows the user to leave more generous amounts of headroom, the best option for a 16-bit device is to get the level as high as possible without clipping, so as to make best use of the available resolution.
I conducted speech recording tests using an inexpensive studio capacitor mic with the phantom power provided by the X2U — and the results were really very good, with no audible background noise and a clean, clear sound. The tests were repeated using two Shure wired mics and I got similarly good results in both cases. All in all, this is a simple but very well executed version of the USB mic-preamp concept.
£139.99 including VAT.