Using an analogue mixer with a USB audio interface

When to use this

• Mixers with no USB audio interface at all.
• Soundcraft Ui12 and Ui16.
• Behringer XR12 and XR16.
• Older analogue Mackie and Soundcraft desks.
• Any mixer whose USB port does playback or storage but not computer recording.
• Any situation where the built-in USB recording mix cannot be separated from the microphones.

What to buy

Anything with two line-level inputs and a reliable driver. In rough order of cost:

• Behringer U-CONTROL UCA222 or UCA202. Two unbalanced RCA inputs over USB, and about as cheap as audio hardware gets. These inputs overload easily, so start with the mixer output low and check for clipping.
• Focusrite Scarlett 2i2, Steinberg UR22 or MOTU M2, if you want balanced line inputs and better converters.

The analysis feed does not need a good interface. It needs a working one.

Which mixer output to use

Take the first of these your mixer has:

1. A stereo Matrix output.
2. A pair of linked Aux outputs.
3. Record Out or Tape Out.
4. Control Room output.
5. Monitor output.
6. Main L/R line output.

A Matrix or Aux mix is usually the best of these, because you can build it with the speech microphones left out. Record, Control Room, Monitor and Main outputs normally carry the main mix, microphones included, although on some desks a subgroup or ALT output can be set up to carry only the music. For how to set up the bus itself, see the music-only feed section of Connecting a Sound Mixer to DMXDesktop.

Wiring it up

Match the level, not just the shape of the connector. A mixer output is line level, so it belongs in two line inputs on the interface.

• Use two separate inputs: one for left, one for right.
• If the interface has a LINE / INST or LINE / MIC switch, set both inputs to LINE.
• Keep phantom power (48V) off for these inputs.

If the mixer has RCA Record Out

A plain stereo RCA-to-RCA cable into an RCA interface such as the UCA222. Record Out L to input L, Record Out R to input R.

If the mixer has quarter-inch outputs

Into balanced TRS line inputs, use two TRS-to-TRS cables. Into an RCA interface, use two 6.35 mm to RCA cables. Left output to the left input, right to right.

If the mixer has XLR outputs

On many interfaces the XLR sockets are microphone inputs. Do not go XLR to XLR just to keep the connection balanced. Use XLR-to-TRS cables into the interface's TRS line inputs instead. Into an RCA interface, use correctly wired line-level XLR-to-RCA cables.

Computer setup

Windows

1. Connect the interface and let Windows install its driver.
2. If the manufacturer supplies an ASIO driver, install it and select it. If not, the ordinary stereo recording input is fine.
3. In DMXDesktop, open Settings → Audio and select the interface. A two-input interface only has channels 1 and 2 to offer.

macOS

1. Connect the interface.
2. Open Audio MIDI Setup and confirm it appears as an input device.
3. Select it in Settings → Audio and use channels 1 and 2.
4. Grant audio input permission when macOS asks. It only asks once.

A two-input interface has no channels above 2, so the ASIO rule that applies elsewhere in this guide is irrelevant here. This is one of the reasons the analogue method is such a dependable fallback.

Setting the level

1. Mute or turn down the PA while you are making connections.
2. Set the interface input gain low, if it has one. On an RCA interface such as the UCA222, start with the mixer output well down, because those inputs overload easily.
3. Play a loud, representative section of the music.
4. Bring the mixer's output up until DMXDesktop's meter reads healthily.
5. Back off before it pins at the top. Clipping destroys the dynamics the analysis needs.
6. Check both channels move.
7. Label the output on the mixer, and save the scene if it has one.

Troubleshooting

Very quiet, even with everything up

Check the mixer's output level and its master, that the music is actually routed to that output, the interface's input gain, and that the cables are wired for the sockets at both ends. If all of that is right, try a different line output such as Record Out, Aux Out or Control Room Out.

Distorted even at low console levels

The output is too hot for the input, which usually means a headphone amp or a speaker-level output. Stop and check what the socket actually is before you damage the interface. An RCA interface such as the UCA222 also overloads more easily than a balanced one, so turn the mixer output down.

Thin or hollow sound, with parts of the music missing

A stereo output is going into a single balanced input, so one side is cancelling the other. Use a stereo breakout cable into two inputs.

One channel only

One side is not connected: a cable is unplugged or faulty, the second output is not patched, or a stereo breakout cable is wired or plugged in wrongly. Swap the two cables at the interface to see whether the fault follows the cable or stays with the input.

Hum or buzz

Usually a ground loop between the console and the computer. Balanced connections help where both ends support them. With an RCA interface, put a line-level isolation transformer (a ground loop isolator) between the mixer and the interface. An ordinary DI box is the wrong tool here, because it turns the signal into microphone level.

Still not working

Work through the shared checks in Connecting a Sound Mixer to DMXDesktop, which covers the faults that are not specific to one console. If you need to contact support, have these five things ready, because they resolve most cases immediately:

1. The exact mixer model.
2. Your Windows or macOS version.
3. How the mixer is connected, and which USB port you used.
4. Which device you picked in Settings → Audio.
5. Which left and right channel numbers you selected.

For a console with a multichannel USB interface, a screenshot of the mixer's USB output patch is worth more than any log file.