When it comes to professional audio interfaces, Universal Audio has long stood out for its blend of excellent AD/DA conversion and onboard UAD DSP processing. Their Apollo series has become a go-to choice for musicians, producers, and audio engineers seeking top-tier performance in both studio and mobile setups. The Apollo x4 carries this legacy forward in a desktop-friendly package, offering four preamps, versatile connectivity, and the real-time effects processing that made UA famous. In this review, we’ll dive into its key features, audio performance, and overall user experience to help you determine if the x4 is the right interface for your workflow.
Overview & Build Quality
Compact Yet Sturdy Desktop Form Factor
The Apollo x4 condenses many of the capabilities of larger Apollo rackmount interfaces into a relatively small footprint that fits comfortably on a desk. Its solid metal enclosure feels rugged enough for portable setups, making it a great choice for mobile recording rigs or smaller home studios.
Familiar Apollo Aesthetic
The sleek, black metal casing with a large monitor control knob on the top panel immediately identifies it as part of the Apollo family. An easy-to-read LED display ring around the main knob gives you instant visual feedback on levels, a hallmark of UA’s modern designs. On the front, you’ll also find two convenient Hi-Z inputs for guitars or other instruments, along with headphone outputs for quick access.
I/O & Connectivity
- Four Unison Preamps
- The x4 offers four mic/line inputs on the back, all featuring UA’s celebrated Unison technology. Unison integrates hardware and software to emulate the impedance and gain stage characteristics of classic microphone preamps (Neve, API, SSL, etc.). This means you can color your recordings at the source, capturing authentic vintage tone before the signal even hits your DAW.
- Line Outputs & Monitor Outs
- In addition to the main monitor outputs, the x4 includes two balanced line outputs for external gear or alternate monitor mixes. If you’re patching in hardware processors or sending signals out to other devices, these extra outputs come in handy.
- Optical Expansion
- An ADAT/SPDIF optical input allows up to eight additional channels of digital input, great for expanding your system with an external multi-channel preamp or digital device.
- Headphone Outputs
- Two separate headphone outputs on the front facilitate easy collaboration during tracking sessions, with independent level controls.
- Thunderbolt 3 Connectivity
- The x4 uses Thunderbolt 3 for high-bandwidth data transfer, ensuring minimal latency even when running multiple UAD plug-ins in real time. Mac users can connect directly; PC users need a compatible Thunderbolt 3 port and sometimes additional configuration.
Conversion & Audio Quality
Next-Generation A/D-D/A Performance
Universal Audio’s Apollo x series boasts improved converters over earlier Apollo models, delivering 129 dB dynamic range on the output and ultra-low THD+N. Translated into practical usage, the x4 captures fine detail and represents audio accurately, from the subtlest acoustic guitar nuances to the full roar of a drum kit.
Transparent Yet Musical Sound
While the raw converter path is clean, you have the Unison feature to add classic coloration if desired. This combination of pristine capture and optional vintage-style mojo arguably makes the Apollo x4 one of the most versatile small-format interfaces on the market.
Onboard UAD-2 DSP & Real-Time Effects
A standout Apollo feature is its onboard UAD-2 DSP processing, which grants access to a library of revered analog hardware emulations. When you record or mix through these UAD plug-ins, the processing power is offloaded to the interface rather than your computer, yielding two major benefits:
- Low-Latency Tracking – You can record with near-zero latency while monitoring through plug-ins such as Neve 1073, LA-2A, or 1176 emulations. This real-time environment is especially valuable for vocalists who want to hear reverb or compression without audible delay.
- Relieves Host CPU – The UAD DSP handles the plug-in processing, letting your computer handle the DAW’s tasks without strain. For large sessions with many plugins, this can be a massive advantage.
The x4 typically ships with a UAD plug-in bundle (which varies depending on current promotions), giving you essential mixing tools right out of the box. You can expand your library via UA’s online store as well.
Console Software & Workflow
UA Console Application
The Apollo x4’s routing, monitoring, and real-time plug-in configuration are managed through UA’s Console software. With an intuitive mixer-style interface, the Console app allows for:
- Channel Inserts: Add UAD plug-ins to any input channel for real-time processing.
- Aux Sends: Create cue mixes for performers or add time-based effects like reverb without affecting the recorded signal (if desired).
- Session Recall: Save and load entire setups, ideal if you frequently switch between different recording or mixing scenarios.
DAW Integration
All Apollos are Core Audio (macOS) or ASIO (Windows) compliant, ensuring compatibility with popular DAWs like Pro Tools, Logic, Cubase, Ableton Live, and more. Once set up, your DAW sees the Apollo x4’s I/O, and you can choose to track with or without the UAD processing. The synergy between UA Console and your DAW is a critical part of why many professionals opt for Apollo interfaces.
Comparison to Other Apollo & Competitor Interfaces
- Apollo Twin X
- The Apollo Twin X is smaller, featuring two mic/line preamps and fewer outputs. It’s more budget-friendly if you only need two inputs, but the x4 offers double the Unison inputs, making it more versatile for multi-mic recordings.
- Apollo x6 / x8 / x8p
- These rackmount Apollos provide more I/O channels, making them more suitable for full-band recordings or studios requiring lots of analog ins/outs. However, the x4 excels for a streamlined desktop workflow with four preamps in a more portable device.
- Competitor Interfaces (e.g., RME, Focusrite, Apogee)
- While other premium interfaces also provide excellent conversion and stable drivers, the UAD DSP ecosystem remains unique to Universal Audio. If real-time plug-in processing and premium analog emulations are priorities, the Apollo x4 remains in a league of its own.
Pros & Cons
Pros
- High-End Conversion: Pristine AD/DA ensures detailed and accurate captures.
- Unison Preamps: Authentic hardware preamp emulations at the input stage.
- Onboard UAD DSP: Real-time plug-in processing with near-zero latency.
- Four Mic Inputs: More versatile for multi-mic or small ensemble recordings than the Apollo Twin.
- Sturdy Desktop Design: Compact yet durable for both studio and mobile use.
Cons
- Cost: The UAD ecosystem requires a premium investment in both hardware and additional plug-ins.
- Thunderbolt 3: Requires modern, compatible ports—PC users, in particular, must verify system compatibility.
- DSP Limitations: The x4’s DSP chips can run out of processing power if you load many high-demand plug-ins at once. Larger Apollo rack units often have more DSP chips.
Final Verdict
The Apollo x4 from Universal Audio strikes a sweet spot between the portability of the Apollo Twin and the expanded I/O of the larger rackmount Apollos. With four Unison preamps, high-end conversion, and powerful onboard DSP, it offers a professional recording solution that’s equally at home in a personal studio, a mobile rig, or a small commercial setting. Yes, the price tag is relatively steep, and the Thunderbolt requirement can be a hurdle for certain users—but the audio quality, real-time UAD processing, and robust build make it a worthwhile investment for those aiming to elevate their productions.
If you need multiple mic inputs, crave top-shelf preamp emulations, and want the flexibility of low-latency DSP tracking, the Apollo x4 is among the best desktop interfaces on the market. It continues the Apollo tradition of “recording like a pro”—offering an ideal blend of tone, technology, and workflow that few competitors can match.
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