Choosing an audio interface is difficult because price, specifications, drivers, features and real-world usability do not always move together. This guide explains what the published numbers can reveal, but also where a specification table stops being useful.
Start with the work you need to do
Price tiers are only a rough guide. Even inexpensive modern interfaces may support 24-bit recording and high sample rates, while a more expensive model may justify its price through additional inputs, stable low-latency drivers, monitor control, digital expansion or support rather than an obvious change in sound.
Before comparing measurements, decide how many microphone, instrument and line inputs you need at the same time. Check the required outputs, headphone mixes, MIDI, loopback, digital connections and whether the manufacturer still supports your operating system. For recording, available microphone gain and noise performance matter; for monitoring, reliable drivers and practical volume control may matter more than a tiny difference in converter distortion.
A small interface can be entirely adequate for professional work when its connections match the job. A larger or more expensive unit becomes valuable when it removes a real limitation from the workflow. The related guide on building a music-production setup can help put the interface in context.
How to read the specifications
Signal-to-noise ratio, dynamic range and THD+N are useful, but only when the measurement conditions are comparable. Manufacturers may use different gain settings, bandwidths, weightings and reference levels. A larger number is generally better for signal-to-noise ratio and dynamic range; a smaller number is generally better for distortion, but neither figure alone tells you whether an interface fits your work or sounds audibly better.
The following tables are a legacy comparison compiled from the figures available for these product generations. They are useful for broad orientation, not as a controlled laboratory ranking. Confirm current specifications in the manufacturer's manual before buying, and do not compare a differently weighted or referenced figure as if it were measured under identical conditions.
Microphone preamp signal-to-noise ratio
Published or compiled microphone-input signal-to-noise figures, shown in dB(A):
| Interface | dB(A) |
|---|---|
| Apogee Boom | 122 |
| Focusrite Clarett 2Pre USB | 119 |
| Focusrite Vocaster Two | 112 |
| Focusrite Scarlett 18i20 Gen3 | 110 |
| Focusrite Scarlett Solo Gen3 | 110 |
| Focusrite Scarlett Solo Gen2 | 106 |
| MOTU UltraLite-mk5 | 119 |
| MOTU M2 | 115 |
| Audient iD44 MKII | 116 |
| Audient iD4 and iD14 MKII | 113 |
| Audient EVO 4 | 115 |
| Audient iD14 | 112 |
| RME Babyface Pro FS | 116 |
| Universal Audio Volt 2 | 112 |
| SSL 2 | 110 |
| Tascam US-2x2HR | 110 |
| Antelope Zen Go | 110 |
| PreSonus Studio 24 | 107 |
| PreSonus Revelator io44 | 102 |
| PreSonus AudioBox GO | 90 |
| Behringer UMC404HD | 104 |
| Behringer UMC202HD | 100 |
| Behringer UMC22 | 85 |
| Behringer UM2 | 84 |
| M-Audio AIR | 103 |
| M-Audio M-Track Solo/Duo | 88 |
| Steinberg UR22C | 103 |
| Steinberg UR22mkII | 100 |
| LEWITT CONNECT 6 | 100 |
The lower entries show less noise margin on paper, but a brand-wide conclusion would be misleading. Recording noise also depends on microphone sensitivity, required gain, source level and the room. Treat the figures as one filter in the decision, not a verdict on whether a recording can be professional.
Output dynamic range
Output dynamic range describes the span between the noise floor and the maximum level under the stated test conditions. More range is useful, but a small difference does not automatically make one interface sound clearer or less muddy in normal listening.
| Interface | dB(A) |
|---|---|
| Apogee Boom | 122 |
| Focusrite Clarett 2Pre USB | 118 |
| Focusrite Scarlett 18i20 Gen3 | 107 |
| Focusrite Vocaster Two | 108 |
| Focusrite Scarlett Solo Gen3 | 108 |
| Focusrite Scarlett Solo Gen2 | 106 |
| MOTU UltraLite-mk5 | 125 |
| MOTU M2 | 122 |
| Audient iD44 MKII | 126 |
| Audient iD4 and iD14 MKII | 125 |
| Audient EVO 4 | 112 |
| Audient iD14 | 117 |
| RME Babyface Pro FS | 125 |
| Universal Audio Volt 2 | 110 |
| SSL 2 | 112 |
| Tascam US-2x2HR | 111 |
| Antelope Zen Go | 128 |
| PreSonus Studio 24 | 104 |
| PreSonus Revelator io44 | 102 |
| PreSonus AudioBox GO | 100 |
| Behringer UMC404HD | 107 |
| Behringer UMC202HD | 107 |
| Behringer UMC22 | 92 |
| Behringer UM2 | 92 |
| M-Audio AIR | 102 |
| M-Audio M-Track Solo/Duo | 96 |
| Steinberg UR22C | 107 |
| Steinberg UR22mkII | 103 |
| LEWITT CONNECT 6 | 104 |
The table shows meaningful differences at the extremes, but the middle of the list should not be overinterpreted. Driver stability, output level, headphone performance and the monitoring chain can have a larger practical effect than a few decibels in a differently documented specification.
THD and practical conclusions
Total harmonic distortion plus noise is also useful only with its test conditions. A missing figure is not evidence that a product performs badly, and an extremely low published value does not outweigh unsuitable inputs, unstable drivers or insufficient gain.
On the compiled figures, models such as the Focusrite Clarett 2Pre, MOTU UltraLite-mk5, RME Babyface Pro FS and several Audient interfaces offer strong measured performance. That does not make them the automatic winners for every buyer. A two-input recording setup, a multichannel drum session, a mobile rig and a mastering room have different priorities.
My practical conclusion is to shortlist by connection count, driver and operating-system support, gain, monitoring features and budget first. Use comparable measurements to separate the remaining choices, then test the actual workflow if possible. If the main purpose is microphone recording, the preparation advice in Tips for Creating a Proper Vocal Recording will often improve the result more than moving between two already competent interfaces.