This is a fantastic USB soundcard. It supports 4 simultaneous inputs and outputs, with 4 mic preamps featuring 48V phantom power. It also has MIDI in and out, a headphone socket, and control knobs to control input gain and output levels.The inputs are available on both balanced XLR and balanced line input sockets. Outputs 1 and 2 are available on balanced XLR, balanced line, and unbalanced RCA phono. Outputs 3 and 4 are available on unbalanced line and unbalanced RCA phono connections. All four channels also feature mono insert returns, allowing for use of external hardware effects.Controls are as follows: four input gain knobs, one per channel, as well as a button to switch between mic level and line level input signals. On the output side, there's a single knob to control the level of outputs 1 and 2, another for the Phones output, and a Mix knob. This knob controls the hardware mixing between input and playback levels - if turned towards the left, any signals coming into the inputs will be sent to the main outputs 1 & 2. This allows monitoring of any inputs alongside anything being played back, allowing you to record one or more instruments or vocals while listening to previously recorded tracks. This is done entirely in hardware with zero latency and not requiring any software setup. If you'd prefer to keep the input signals out of the playback, turn this knob all the way to the right, marked "PB" for Playback.Four buttons are also provided to independently pad each input channel. Finally there's a button that controls the Phones output, configuring whether it is monitoring outputs 1&2 or outputs 3&4. This allows for A/B switching between two mixes, if you set up the outputs appropriately in software.The device connects to your computer via standard USB 2 cable. It is provided with a small DC power supply, enabling use of the device without an active USB connection. The power supply can be used in addition to the USB connection to ensure a clean, noiseless power feed.On Mac it will be detected immediately, on Windows you need to download drivers from the Behringer website. These drivers include both standard Windows audio and ASIO support, and installs a systray icon which activates a control panel. This control panel allows changing buffer settings, bitrate, sample rate, and so on.I have used the device in both Windows 10 and macOS High Sierra, using Adobe Audition, Sony Sound Forge and other audio apps. All apps will see four inputs and four outputs, and each can be used independently in a multi-track project. You can be recording to four new tracks while simultaneously playing back four already recorded tracks.Thanks to the four mic pre-amps, you can record up to four microphones directly into the sound card. Optional 48V phantom power means it can work with condenser mics and any other that need power supplied. It is therefore an extremely handy device to take on the road, allowing you to record and play back with only this soundcard and a computer or laptop, no mixer required. You can control the gain of each input independently. Playback settings are more limited in hardware - you can only control the volume of outputs 1 and 2. Control of outputs 3 and 4 needs to be done in software.Audio quality is excellent. The device supports full 24bit / 192khz in both recording and playback. I am no expert sound engineer, but I have made recordings direct into the device from a couple of Behringer condenser microphones, and I have used it for playing back up to four channels simultaneously in live theatre productions. In all cases it sounded great, with no noticeable noise, hum or distortion.This is a really excellent and flexible sound card. It has enough inputs and outputs to cover a variety of requirements, yet is still small and portable enough to be thrown in a bag and taken anywhere it's needed. As mentioned I've used it to record from a couple of condenser microphones, and also to provide the music and sound effects for several theatre productions.In addition I'm also now using it as my main PC sound card. Because it has four outputs, I can use it for basic quadraphonic surround sound - there's a setting for 4.0 surround in Windows and macOS sound preferences. Connected to a decent amplifier and speakers it provides really superb audio quality for music and watching movies.Highly recommended for anyone who needs top quality recording and playback of up to four in and four out. I think it's excellent value for the money considering everything it can do.