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A Simple and Reliable Way to Wrangle Signals into a Common Output

$199.00 street

By Jon Chappell





When you’re a performing multi-instrumentalist, you quickly learn what a summing mixer is, because it’s an indispensable piece of stage gear. Basically, it’s a box that groups multiple inputs into a common output (mono) or outputs (stereo). Signal-routing-wise, it’s like a no-frills mixer, but a lot smaller and simpler electronically, and so is easily tossed into a gig bag or the back of an amp. In one typical situation, you would plug an amplified acoustic, the stereo outputs of a keyboard, and the output of your last stompbox into the summing mixer. The outputs are ganged together (“summed”) in an electrically kosher way and sent to a single mono output or to stereo outputs, which you would then plug into an amp, mixer, or P.A. In a mono setting you can use the summing mixer’s output to feed a single input of your guitar amp. Summing mixers can be used in small studios and makeshift recording setups, and they have secured a place in large-scale DAW recording as well.



Unit Audio offers a trio of summing mixers: the Milli-Unit ($149.00), the Micro-Unit ($199.00), and the Unit ($335.00). All are similar with regard to internal electrical specifications and differ only in number of inputs and inclusion of panning switches. My review model was the middle-of-the-pack $199 Micro-Unit, which has 8 inputs (as opposed to 16 on the Unit) and panning switches for Inputs 1 and 2 (versus none on the Milli-Unit).



The Micro-Unit is ruggedly built and handsomely designed. With its lacquer-coated gloss-enamel paint job, uniform black-on-green color scheme, and smart hardware layout, it looks more like one of my higher-end stompboxes than the utilitarian direct boxes I would throw into a road case with my mic stands. The Micro-Unit features 8 Neutrik TRS inputs arranged in four rows of two on the top panel, with 2 Neutrik TRS outputs on the front. The only other functionality are the two DPDT switches on the top that selectively switch the “pan” of Inputs 1 and 2 from Left and Right to Center (both L and R). That means that if you plug a single cable into Input jack 1, you can throw switch 1 down to “C,” which will output the signal to both Outputs.  I like having this option, and it allows me to accommodate both mono gear (e.g., guitars) and stereo gear (keyboards, drums submixer) by plugging the mono inputs into 1 and 2 and the stereo inputs into the three input pairs 3/4, 5/6, and 7/8.




The Micro-Unit is a passive unit, and so requires no external power and won’t color your sound. It’s basically a box of resistors that accommodates many input signals and wards against crosstalk. The output is standard mic level (220 ohms), so a preamp is needed to supply 30–40dB of makeup gain. The manual advises that this is an opportunity to add a little color to your signal (using a transformer-based preamp, such as a Neve or any model based on that design), or not, if you use a Sytek preamp or its ilk. Whichever route you go, the Micro-Unit keeps the price down and simplicity of its ethos at the forefront by choosing to exclude a preamp, assuming that you probably have at least one of these hanging around. This is a savvy choice, especially for studio recordists. The high-quality Neutrik connections provide a firm grip on your cables’ jacks and the unit sits firmly in place, whether on a tabletop or the floor of a studio.




Although the live applications are obvious, the Micro-Unit has recording applications as well. A common practice in DAW recording these days is not to take all the multitrack material internally to the stereo bus, but to bring certain stems out via your interface’s analog outputs and bring them back into the DAW through the inputs, going to the stereo mixdown bus that way. This avoids a number-crunching burden on the computer’s processor that is not ideal for the best sound. Instead of internally mixing down, say, 8 channels of drums, the DAW now has to accommodate only two, originating from the outputs of the summing mixer. Unit Audio supplies a helpful graphic that shows the routing of this scenario (see Fig. 1).




Fig. 1. Instead of internally summing multiple tracks to stereo, you can improve your mix by routing those tracks out of your computer, summing them to stereo via the Micro-Unit, and reintroducing them to the DAW as a stereo mix. (Click to englarge.)



The Micro-Unit is was built for just this purpose and is perfect for two very common stem groups, drums and bass—the two sounds that can often throw off the whole mix while you try to compensate for them if you use the stereo bus as a reference. Summing these groups externally (through the Micro-Unit) rather than internally (with all multi-tracks routed directly to the stereo bus) isolates these tracks from the internal summing process is considered the best use of DAW and external units. The M-U helps share the mixing burden over two systems, within and from outside of the DAW. I tried this with a mix containing 10 separate drum tracks. By taking the eight most problematic (thundering bass and toms, loud snare, and sizzly cymbals), routing them out of the interface to the Micro-Unit, and re-introducing them in an already balanced submix, I could hear better separation and a definite improvement in overall clarity. The difference may be subtle, and I had to A/B the results, but it was definitely there. Of course it helps to have a nice tube pre on hand!




Hand-wired, hand-assembled, and individually tested in the U.S., the Micro-Unit is a deceptively simple unit, but has many uses, both in live and studio situations. If you’re using it onstage, the 8 inputs allow more or less permanent connections of your gear. Its transparent sound ensures signal integrity, especially for such critical sounds as solo acoustic guitar. If you want to bring the now-common practice of external summing to your DAW recording process—and at an affordable price—you can’t beat the Micro-Unit. It’s so easy and non-invasive to introduce that once you use it, the Micro-Unit will quickly become an indispensable piece of gear in your live and studio setup.



Jon Chappell\\_HCBio\\_101x101.jpg


Jon Chappell is a guitarist and the Senior Editor of Harmony Central. He has contributed numerous musical pieces to film and TV, including Northern Exposure, Walker, Texas Ranger, All My Children, and the feature film Bleeding Hearts, directed by actor-dancer Gregory Hines. He is the author of The Recording Guitarist: A Guide for Home and Studio (Hal Leonard), Essential Scales & Modes (Backbeat Books), and Build Your Own PC Recording Studio (McGraw-Hill), and has written six books in the popular Dummies series (Wiley Publishing).

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