Universal Audio Apollo x4 Gen 2

The Universal Audio Apollo x4 is the step up from the Apollo Twin X that adds two more Unison preamps, a second headphone output, ADAT expansion, and more output routing — while keeping the compact desktop form factor that made the Twin X popular. It is the Apollo for producers who have outgrown two preamps but do not need a rackmount unit.

The four Unison preamps are the same circuit as the Twin X — hardware-integrated emulations of Neve 1073, API 512c, Manley VARI MU, and other vintage preamp designs, processed in real time on the onboard UAD-2 QUAD Core DSP chips. The QUAD Core gives meaningful headroom over the Twin X DUO for running multiple UAD plugin instances simultaneously. Two optical Toslink ports add ADAT expansion — up to 8 additional channels at 44.1/48kHz — making the x4 capable of handling a full band or drum kit via an external preamp bank.

The 12-in/18-out configuration includes four balanced line outputs, two monitor outputs, and two independent headphone outputs with separate level controls. The second headphone output is one of the most practically useful additions over the Twin X for tracking sessions. Like all Apollo interfaces, the x4 runs from Thunderbolt 3 — a dedicated Thunderbolt port is required, not a standard USB-C connection.

UAD plugin licences do not transfer with the hardware when buying used — these stay with the original owner's UA account. Factor this in when comparing used prices, as the hardware value and the plugin value are separate.

On the used market the x4 is liquid and well regarded. The Gen 2 update improved converters and the front panel encoder reliability. Gen 1 units are fine but Gen 2 is worth seeking out.

Who Is This For?

• Producers who need four Unison preamps and ADAT expansion in a desktop unit
• Studios tracking multiple sources simultaneously who want UAD processing without a rack
• Apollo Twin X owners who need more I/O and a second headphone output
• Anyone already in the UAD ecosystem looking to expand their hardware