Check the listing for details. Universal Audio Apollo x4 Gen 2 Essentials+ Thunderbolt Audio Interface with UAD. Condition: New. Listed at 1979.99 USD. Now Ready for Your Studio: The Best Apollo Yet Boasting next-generation elite-class AD/DA, Universal Audio’s Apollo x4 Gen 2 yields the lowest distortion and widest dynamic range of any desktop Apollo to date. The Apollo x4’s powerful onboard plug-in processing provides you with award-winning emulations of tried-and-true studio classics that you can track through in real-time using UA’s vaunted Unison preamp technology. Of course, you can also combine Apollo x4’s onboard DSP with your host computer’s native processing to create a powerhouse hybrid workflow. Meanwhile, you’ll be able to mix confidently in any room or through headphones using Apollo Monitor Correction (an optional add-on); plus, Bass Management optimizes your subwoofer for maximum low-frequency detail.