There are two built-in high-quality Jasmine™ mic preamps with Neutrik™ Combo XLR input jacks for microphone, line and direct instruments and 48-volt phantom powering for studio microphones. MixerFace R4 comes with an internal, long-lasting Lithium-ion Polymer rechargeable battery that runs it for about eight hours. Professional features continue with 1/8-inch mini TRS balanced studio monitor outputs for driving powered monitors making the unit viable as your project studio's main USB recording interface.

I was excited to plug everything into R4 and give it a go! For stability when connecting, I liked that there is a 1/4-inch--20 threaded hole in the center of the bottom plate the mates to video camera stands or (as I used) an adapter to match a standard 5/8-inch threaded mic stand. With the R4 firmly attached to a mic stand, I was ready to start plugging in cables--and there can be quite a few to take full advantage of the unit's tremendous capabilities.

I started by recording street noise for a background effect in a mix I was doing. I connected two Gauge Precision ECM84 small diaphragm cardioids in an X-Y stereo configuration. I switched on phantom power for these mics and switched in the R4's 6dB/octave, 130Hz high pass filters to reduce the low frequency street rumble. To prevent accidental operation especially while in record, all the switches on the MixerFace R4 are recessed and require a small pointed tool to operate--I used a jeweler's screwdriver but in a pinch a toothpick will work.

Next I connected an Apple USB-to-Lightning adapter (not included) or for Android users, use a micro USB OTG cable (also not included) to interconnect the R4 with your phone, tablet or computer. iOS programs like GarageBand, Sonoma Wire Works Four-Track or IK Multimedia iRig Recorder all worked fine on my iPhone X.

I also tried 24-bit 48kHz recording using MixerFace R4 with Presonus Studio One 4 running on my studio's computer. Using a micro USB cable, it comes up in the list USB interfaces in the setup page (without installing any driver) as I'm sure it does in Pro Tools and others.

With the mics plugged in and my Audio-Technica ATM-M70x headphones connected, I could monitor directly from the mics audio inputs with no latency. I liked the Peak and Signal present LEDs--it's reassuring that you got working mics. The unit's channel 1 and 2 Gain controls also feed the four-channel monitor mixer with Ch1 and Ch2 crossfade/blend pots to mix live audio with any pre-recorded audio coming in from you DAW.

I tried connecting a stereo mini TRS line cable to the Aux 3/4 input to play a stereo backing track coming from a CD player. It mixes in along with the microphone's audio at whatever mix you arrive at and hear in the monitor. The MixerFace R4 outputs stereo audio via the headphones, monitor speaker outs, the Lin Out, and your DAW USB connection all at the same time.

You can monitor live audio through your DAW if you want but there will be latency. I mostly used the stereo mode monitoring position because I was recording in stereo but the mono position is louder if you need it. Also you'll probably want to monitor in mono mode when recording an instrument (acoustic guitar or keyboard etc.) and your own voice at the same time but to separate tracks in your DAW.

The Jasmine microphone pre-amps sound good and are sensitive and noise-free. There is about 55dB of gain available and I had no problem recording ambient street sounds--I was never "starved" for mic gain. I tried my Fender Strat direct in and it worked great! I just switched over to Hi-Z (another recessed toggle switch) for that Input 1 and I could keep the +48-volt phantom power on for my Soundelux U195 large diaphragm microphone plugged into Input 2. Awesome!

As an all-around compact USB interface/mixer--it even has a balanced mini TRS jacks for driving powered monitors, CEntrance got it all right with the MixerFace R4. Its small size, great sound, and portable battery operation (ran all day powering two condenser mics) makes it a winner for lap top producers, bloggers, journalists, and attached to video cameras.