Set up a USB audio interface for your sound desk.

Set up a USB audio interface in six steps

The first two are about buying and plugging in. The rest are settings you make once.

1. 1

   Choose an interface that does only what this job needs

   First check whether you need one. A mixer with USB audio that can send the speech mix over USB may connect straight to the computer: see if your desk connects by USB below, and the mixer guide compares the options. If your desk cannot, an interface is the answer.

   The interface has one job here: take a line-level feed from the desk and present it to Windows as a recording device. Almost any small interface sold for home recording can do that. Look for these, in this order:

   • A line input. Either a dedicated line socket, or a combined socket that takes an XLR plug or a 6.35 mm plug. A desk output is line level, so the input must be able to take a line feed. How an interface selects line varies; step three explains what to check.
   • A level control you can reach. Most interfaces have a gain knob. You will set it once with the loudest speaker and leave it. Some line inputs have fixed gain or a software control instead, which also works.
   • USB power from the computer. Most small interfaces take their power from the USB cable. A few need a separate power supply; the label or the manual says so.
   • Windows support from the maker. Many interfaces appear in Windows the moment they are plugged in. Some need the maker’s driver first. Check the maker’s page for your model before the day, not at the desk.

   One input is enough, and two is common. You do not need a headphone output, phantom power, effects or a built-in mixer for this job, though they do no harm if they are there. An ordinary USB microphone is not a substitute: it has a microphone built in and no line input for a desk.

   

   If the only sockets on the interface are labelled for microphones, check the manual before buying. Many combined sockets take a line feed on the jack side; some are microphone-only.

2. 2

   Plug it in the right way round

   Plug the USB cable into a socket on the computer itself to start with. A direct connection gives the interface the power it needs and removes one thing that can drop out mid-event. A powered hub or dock may work, but it is one more thing to rule out if the interface disappears. Do it before you open the desk app.

   If the maker says a driver is needed, install it now and restart if it asks. Then check in Windows: open Settings, System, Sound, and look under Input. The interface should be in the list. If it is not there, the app cannot see it either, so fix that first.

   Run a balanced lead from the spare output on the desk to the interface, as the mixer guide shows. Check which plug the interface wants for line level: on many combined sockets it is the centre 6.35 mm jack, so the lead from an XLR desk output may need a 6.35 mm TRS plug at the interface end.

   Sound desk spare output

   XLR / TRS

   USB interface line input

   USB

   Windows computer Sound settings, then the desk app

3. 3

   Set the input on the interface itself

   Before any sound, set the front of the interface. These switches are where most “it is too loud and crackly” calls come from:

   Check how your interface selects line level. Many combined inputs use the centre 6.35 mm jack for line signals, with instrument mode switched off, and the XLR side may be microphone-only even though both plugs fit the same socket. Some interfaces have a mic/line switch instead. The manual says which.

   • Use the line input for the desk, with instrument or Hi-Z mode off.
   • Turn the gain down, nearly to the bottom. You will bring it up in step five.
   • Leave phantom power (48 V) off. A line feed does not need it.
   • If the input overloads with the gain low, check the desk send level first, then use the interface’s input pad if its manual recommends it. Instrument or Hi-Z mode is not a cure for a feed that is too hot.

   Controls labelled monitor, mix or direct usually affect only what you hear in headphones on the interface. Check the manual if you are unsure.

4. 4

   Choose it in the desk app

   Open the desk app. In the Input panel, with Live device selected, open the device picker and choose the interface by name. The picker lists every recording device Windows has; if the interface was plugged in after the app opened, press Refresh and it appears.

   Under the picker the app shows a format line such as 48 kHz · 2 ch → 16 kHz mono. It describes the device as Windows sees it. Nothing about it needs changing, and an interface with two inputs showing 2 ch is normal when only one is connected.

   The app remembers the device you chose and picks it again next time. If a restart or a different USB port makes the interface appear under another name, choose it again.

   The meter moves as soon as a device is chosen, before you press Start streaming. Nothing is sent until you do.

5. 5

   Bring the gain up and read the meter

   Have the loudest speaker talk at the level they will use on the day. Raise the interface gain until the meter in the desk app moves well into the green on every sentence and the red segments never light. If the meter is still, jump to the troubleshooting cards below. Watch the interface’s own input or clip light as well: a green meter in the app does not prove the input was clean, because sound can distort before it reaches the app. If the interface clips, lower the level coming in or the gain; turning the Windows recording level down afterwards does not repair a distorted signal.

   • If the meter will not come up even with the gain well open, check the recording level for that device in Windows Sound settings, then the send level on the desk. The meter in the app follows what Windows delivers.
   • If it touches red with the gain low, turn the desk send down first, then try the interface pad.
   • If it keeps moving when nobody is talking, the desk send may be carrying something it should not, or the room noise or the input’s own noise is being picked up. Mute the send on the desk to find out which. Fix it on the desk, not in the app.

   The help centre page Setting the level covers reading the meter in more detail.

   Mark the gain knob with a dot of tape once it is right. If somebody bumps it, the tape shows where it was.

6. 6

   Make it the same every time

   An interface that worked on Tuesday is the one that fails on Sunday because something was moved. Take two minutes to make it repeatable:

   • Use the same USB socket each time. Windows can list a device under a different name when it is plugged into a different socket.
   • Keep the USB cable with the interface and carry a spare of the same length.
   • Label the interface input with the name of the desk output that feeds it.
   • Plug it in and check the meter before the first person arrives, as a habit, the same way you check a microphone.

   Test file mode checks the app and the onward streaming path without using the mixer or the interface. If that works but the live input does not, check the desk feed, the cable, the interface and the Windows input settings.