The Live Connection - The challenges of connecting to a Venue's PA System (aka keeping your sound engineer happy).

Your songs sound great, you've got your stage image down, you've written a killer setlist, and now it's time to take your songs out live. Whilst you may have thought about how to interface with your audience, have you thought about how to interface with the venue?

In a previous life, your author was a professional Live Sound engineer. In fifteen years of working everything from cabaret clubs to 8000 capacity festival stages, I've seen just about every audio connection there is; The Good, The Bad, and The Ugly.

*dramatisation, possibly not based upon actual events which maybe didn't happen

*dramatisation, possibly not based upon actual events which maybe didn't happen

Take it from me, being able to turn up with professional connections, ready to interface with your venue's PA system, gets the sound engineer in a good mood, right from the outset. No one enjoys running around looking for adaptors, or cables which the band should have brought with them.

Here's the lowdown on what you need to know about interfacing your audio outputs to your venue's stage box and keeping your Front Of House (FOH) engineer a happy bunny.

Let's wind back to the early days of PA systems; bands would rely largely on the projected volume of their backline (amplifiers, drums etc) to be heard. PA systems might have had a couple of microphones, tops.

As the 1970s came along, more inputs (and more volume) meant more microphones. At the same time, the Cannon XLR connector came along and pretty much became the industry standard connector for live sound.

Look on any stage, internationally, and you'll expect to see a stage-box with a bunch of female XLR sockets. Each one carries one channel of audio to the FOH mixing desk (sometimes it's split with a monitor desk too). 

The Typical audio connectors you'll find on a live stage: At the top of the image, the XLR connector. Bottom, 1/4" jack plugs - note the balanced TRS (Tip Ring Sleeve) jack plug.

The Typical audio connectors you'll find on a live stage: At the top of the image, the XLR connector. Bottom, 1/4" jack plugs - note the balanced TRS (Tip Ring Sleeve) jack plug.

So why the XLR connector? Two reasons: Firstly, it's a rugged connector which can withstand abuse. Secondly, it's a balanced connector. Balanced connections use a very clever, yet simple electronic principle to ensure that interference and noise is kept to a minimum on long cable runs.

"But! I don't use microphones!" you might say, "Plus I've got loads of electronic gear which only has line outputs! Is the venue going to turn me away?". Well, no, the venue isn't going to turn you away, but presenting your sound engineer with an iPhone as your backing source isn't going to win any favours.

Just because you might be running an electronic source, or "line" level device, doesn't mean you can't interface with your FOH system; it just means we have to be a little more clever...

Once again, in the 1970s, PA hire companies realised that musicians were turning up with a new breed of electronic instrument, which only gave a line-level output. The answer was the DI (Direct Injection) box, which basically ran the line signal through a microphone transformer, effectively emulating a microphone output.

Nowadays, it's commonplace for venues to supply DI boxes to musicians turning up with electronic instruments. The standard input for a DI box is a 1/4" jack plug, just like a guitar lead; bring your own jack to jack leads. It's poor etiquette to expect the venue to provide them.

A typical DI box - this one is a stereo DI which can handle two signals at once. Note the balanced XLR outputs (top) and the unbalanced, 1/4" jack inputs (bottom).

A typical DI box - this one is a stereo DI which can handle two signals at once. Note the balanced XLR outputs (top) and the unbalanced, 1/4" jack inputs (bottom).

Also, if you're turning up with a whole load of 1/4" jack, line-level inputs, think about bringing your own DI boxes, venues only usually carry a couple of DI boxes. If you're turning up with a bank of DI boxes, also think about bringing your own XLR-XLR snake (your FOH engineer will love you).

What if I told you there's another way to interface your sound-card outputs with the PA system though? One which doesn't require messy DI boxes? There's another common balanced connector, and that's the TRS jack plug. All iConnectivity audio interfaces use balanced TRS jack sockets.

Using a TRS 1/4" jack plug (you can tell a balanced jack plug as it has two black bands on the plug rather than one), you can connect a TRS socket to an XLR. Easy huh? Straight into your venue's stage box with just one cable?

Well, there's a potential problem, which has affected all musicians using audio interfaces live. The stage box at a venue can sometimes carry phantom power; if your engineer forgets to turn it off...BOOM! Dead audio interface, instant sad face :(

After seeing the unhealthy aftermath of what happens when phantom power hits an audio interface, we've decided there's a better way. Our new product, due to be launched on October 3rd, will have its balanced audio outputs protected from phantom power via special circuitry.

Bob Malkowski