Audio Interfaces

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This is an updateable recommendation page, not a course article — it includes device models and price estimates, updated roughly every 6 months. The reasoning for why stream audio is taken from the mixer’s aux/matrix output rather than the Main output is in the article “Room Mix vs. Stream Mix”; this page focuses only on what to buy. Note that a mixer’s “control room” output is not the same thing as aux/matrix on many small analog mixers — check your own mixer’s manual.

Once the mixer’s aux or matrix output has been chosen as the source for the stream audio, a device is still needed to carry this signal to the computer. Which device is needed depends on which switching route is used — OBS directly, or an ATEM Mini-series device in front of the switching step.

When the computer receives video through a capture device and OBS handles the switching, the capture device itself typically has no usable audio input for the mixer’s line-level signal. A separate, inexpensive USB audio interface is needed, whose only job is to convert the mixer’s aux output’s analog signal to digital for OBS.

The simplest possible model is enough for this purpose: a Behringer U-Phoria UM2-type USB audio interface with ONE XLR/TRS combo connector (Input 1). The connector accepts either a balanced XLR or a 1/4″ TRS signal directly from the mixer’s aux output — no microphone preamp or phantom power is needed, since the signal is already line-level. This is one mono line input, which is enough in most small church mixer setups, since their aux output is typically mono itself. The UM2’s other input (Input 2) is a separate instrument input for guitar/bass — not a line input, and the device has no separate RCA line inputs.

The price estimate at the time of writing is roughly 25–35 € in European retail and roughly 25–30 USD in the United States — a very inexpensive part compared with the rest of the system. The device is powered over the USB connection, so there is no separate mains charger or country-specific plug type to consider.

[UPDATE REQUIRED: check the current price and availability in your own market before buying — price variation between retailers can be considerable, and the lowest prices may apply only to a limited stock batch.]

Comparable alternatives in the same price range include, for example, Behringer’s own UMC22 or other single-line-input USB audio interfaces with an XLR/TRS connector. A more expensive model is not needed for this task — the extra features paid for (for example, a higher sample rate, more inputs) bring no benefit when the need is a single mono line input. If the mixer’s output needs to be kept genuinely stereo (two separate channels), the UM2 is not enough — a two-combo-input model is needed instead, for example the Behringer UMC202HD, which is in the same price range but offers two full line inputs instead of one.

If an ATEM Mini-series device is added for switching, the situation changes depending on the model.

The ATEM Mini, ATEM Mini Pro, ATEM Mini Pro ISO, and the regular ATEM Mini Extreme (desktop model, approx. $1,250) all receive audio through the same two unbalanced 3.5mm mini-jack connectors — despite the “Extreme” name, none of these has an XLR input or phantom power. The mixer’s XLR/TRS aux output cannot be connected to these directly — an adapter cable is needed, from the balanced connector to the unbalanced 3.5mm connector, that includes a level-attenuating circuit (an attenuator), not just a connector conversion, because the mixer’s line level would exceed this input’s maximum level as-is. In this case, a separate USB audio interface is not needed — it is replaced by a much cheaper adapter cable, but over long cable runs or in noise-prone situations, a separate audio interface is more reliable.

Only the much more expensive, rack-style ATEM Mini Extreme ISO G2 (approx. $2,250) includes a genuine XLR/TRS combo connector with phantom power. Only with this model does the mixer’s aux output connect directly to the device’s own audio input — no audio interface or adapter cable is needed at all. Alternatively, Blackmagic’s own ATEM Microphone Converter accessory (approx. $465) adds an XLR/phantom input alongside any of the cheaper ATEM Mini models without needing to replace the whole device with a more expensive one.

The exact adapter-cable model for the ATEM Mini/Mini Pro/Extreme route is, at the time of writing, still an open research item, with a price estimated at well under 25 €.

[UPDATE REQUIRED: check a suitable adapter-cable model and its price before publishing, if the ATEM Mini or Mini Pro route is relevant.]

This area is less country-specific than many other equipment purchases. XLR and 1/4″ TRS connectors are globally standardized professional-audio interfaces and do not vary by country the way, for example, mains power plug types or voltages do. USB audio interfaces are also typically bus-powered, so no separate mains charger is needed in any country.

One practical check is still always worth doing on site: some budget mixer models offer the aux output only as an unbalanced RCA or TS connector instead of XLR. This does not prevent using the recommended audio interface — it also accepts an unbalanced signal — but the correct adapter cable is worth figuring out in advance, based on your own mixer’s connectors.