Gear Review: Universal Audio Apollo X4 Gen2 Audio Interface

Six years after the original Apollo X4 debuted, the Gen2 version arrives (Oct 2024) with meaningful upgrades, refined hardware, enhanced monitoring capabilities, and a smarter, more flexible Console software experience that now benefits the entire Apollo X series.

After putting it to the test in real-world studio sessions, here’s my review of the Universal Audio Apollo X4 Gen2 Thunderbolt professional audio interface, what it brings to the table (not just metaphorically), and how it performs where it matters most.

First Impressions

The Gen2 model looks a bit sleeker with a more silver-toned finish and feels more refined overall. The updated buttons have a more premium feel, while the familiar LED-based metering system remains crisp and responsive.

There is no flashy touchscreen here; honestly, that’s a plus. What I appreciate most is the large volume knob right in the center. It’s smooth, precise, and great for quick level adjustments during sessions.

The Apollo X4 Gen2 still follows the same I/O layout as the previous generation, but UA really improved the software side.

Real-World Performance

You get 4 Unison mic preamps, each capable of up to 65 dB of gain. What makes Unison special is how it emulates classic analog preamps, not just in sound, but in behavior. It even adjusts input impedance to match the modeled gear, which makes your mics react differently depending on what’s loaded.

Using these preamps with UAD’s classic plugins, like the Neve 1073 or UA 610-B, feels and sounds remarkably close to the real thing. And all controls are easily accessible from the Console software or even from physical controllers like the Softube Console 1 MK3.

The Auto-Gain feature is a major win. It analyzes your input level and sets the gain for you, reducing the chance of clipping or recording too low. If you work with multiple mics or need to move quickly between setups, this is a massive time-saver.

Connectivity

The Apollo X4 Gen2’s rear panel reveals a well-thought-out layout that balances flexibility with clarity. Whether in a home studio or a more mobile setup, this Thunderbolt interface gives you all the I/O you need without clutter.

The Apollo X4 Gen2 offers a smart, studio-ready I/O layout:

• 4 combo mic/line inputs with Unison preamps for flexible tracking
• 2 monitor outs and 4 line outs, all balanced TRS
• ADAT/SPDIF optical I/O for expanding up to 8 additional inputs
• Thunderbolt 3, external power input, and a dedicated power switch

It provides everything needed for professional recording and monitoring, with room to grow for larger sessions.

UAD DSP, Native Plugins & Mixing Workflow

With 4 onboard DSP chips, the X4 can handle real-time tracking with UAD plugins without a hitch. This setup is powerful enough out of the box for most sessions, vocals, guitar, and full bands. For audio mixing with heavy plugin loads, you might consider adding a UAD-2 Satellite.

The bonus? Many UAD plugins are now available as UADx versions, which run natively on your computer’s CPU. That’s a big deal if you want flexibility between real-time tracking and mixing without maxing out DSP.

The Studio Experience

What I’ve loved most is how effortless everything feels. Whether I’m tracking vocals with real-time compression and EQ, recording a guitar with an amp sim, or just switching between monitors, the entire experience is streamlined and responsive.

The integration with Sonarworks SoundID is also a huge bonus. You can load room correction profiles directly into the Console app, which makes it easier than ever to fine-tune your monitoring environment.

Limitations (Worth Knowing)

The X4 Gen2 is a professional Thunderbolt audio interface designed for stereo and 2.1 setups. If you plan to work with surround or Atmos, you’ll need one of the Apollo rack units, like the x8 or x16. That said, for most modern home or project studios focused on stereo production, this won’t be an issue.

One thing to note is that the output is all TRS line level. There are no XLR monitor outs, though that’s not a deal-breaker for most setups.

Who Is This For?

If you’re a serious home studio owner, content creator, or producer looking for:

• Pristine AD/DA conversion
• Real analog feel in your tracking chain
• Real-time effects with no latency
• High-quality Unison preamps
• Expandability for drums or multi-mic setups

…then the Apollo X4 Gen2 checks nearly every box. This audio interface is especially suited for vocal producers, singer-songwriters, or anyone needing top-quality results.

Just be ready to invest. This is not a budget audio interface, but the price is well justified if you value sound quality and workflow.

Final Thoughts

Universal Audio didn’t reinvent the wheel with the Apollo X4 Gen2, and that’s a good thing. Instead, they built on a proven foundation, addressed long-requested features, and created a product that still feels cutting-edge without being overdesigned.

From the big volume knob to the Auto-Gain preamps, from Unison magic to DSP-powered tracking, this audio interface has earned its place at the center of my studio.

If you’re serious about recording, mixing, and producing music at a high level, the Apollo X4 Gen2 is one of the most complete desktop audio interfaces available today.