A Mic Splitter for the Studio

I’ve recently started jamming with some guys around the studio once in a while just for fun, but I ran into a slight problem: I need to keep my drum mics connected to my mic preamps so they’re always ready for recording drum tracks. However, I also needed to connect my drum mics to my live mixer (a Behringer X-Air XR18) so I can use my in ear monitors and add drums to the mix when jamming. So to put it simply, I needed a way to split the signals from my drum mics and send them to a couple of different sets of inputs.

At first I started looking at a simple splitter snake, where each input jack is wired parallel to a pair of output wires that lead to two separate breakouts or fan-tails of XLR connectors. This would have worked fine for my dynamic drum mics, but I also use a pair of condenser mics for overheads, which require phantom power. This complicates things, because you only want the phantom power to be fed from one input (the mic preamp for recording) to the mic, and you don’t want the phantom power flowing to the other input where the mic is being connected (my XR18).

This led me to the idea of using a proper mic splitter. With many such boxes, there’s a single input for each mic and a pair out outputs: a “Direct” output and an “Isolated” output. The Direct output is a hard-wired connection, just as if you were plugging the mic straight in. This Direct out is the one you should connect to your phantom power source. The Isolated output uses a transformer to “isolate” or separate it from the other output. This transformer serves an important purpose: it allows signal to pass from the mic to the input, but will block any DC voltage (phantom power) in either direction. This prevents a situation where the mic is being fed phantom power by two separate sources, and also prevents the one input from feeding it’s phantom power back to the other.

Another nice feature of many mic splitter boxes is a Ground Lift switch. Connecting a single mic to two different inputs can create a ground loop, which can introduce hum, buzz, and other nasty noise into your signal. Breaking a ground loop is accomplished by disconnecting (“lifting”) the ground at one end and leaving it connected at the other. The shield inside the mic cable for the affected channel will continue do its job, because it’s still grounded at one end. Rather than having to open up an XLR connector and clip the shield, the splitter box includes a simple Ground Lift switch that breaks/lifts the ground connection for you on one of the outputs! This way, if you encounter a group loop (buzz or hum on a specific channel), the fix is as simple as the flick of the switch.

After a quick search, I identified the Behringer Ultralink MS8000 mic splitter. This single-rackspace box appears to have everything I need: 8 inputs for my drum mics, a Direct & Isolated output for each, and a Ground Lift switch. It’s also a completly passive box that doesn’t require any power of its own. It also has an interesting “Link” feature which allows you to link or sum pairs of inputs together (1/2, 3/4, 5/6, 7/8) and send the combined outputs out of up to 4 output jacks. This could also be used, for example, to split the signal from a single mic to 4 different outputs. I don’t expect to use this feature now, but it’s good to know the box has that capability.

In any case, I ordered up an MS8000, and it’s on its way as I speak (write). I’ll try to post an update here later after I’ve had a chance to try it out, but from reading all of the positive reviews, I expect that it will do exactly what I need it to.