COVID-19 Update Yes, we are open and shipping! Thanks for your continued support during this difficult time.

Whistle Rock Audio

HZ51X 500-Series Direct Input Kit (Discontinued)

The HZ51X is a 51X series compatible recording DI designed around the attractive Hi-Z Plugin format developed by CAPI and [silent:arts] of the 51X audio group.

The HZ51X allows you to expand your DI tone collection and can add versatility to any mic preamp by adding a full array of DI inputs. It is designed to get the most out of the Hi-Z Plugin format. The 1.1"x1.1" plugin modules are available in DIY kit form from CAPI. Each Plugin offers a unique sonic flavor. With two passive and two active Hi-Z circuits currently to choose from, you can already fill up all four slots offered by the HZ51X!

The HZ51X will host your Hi-Z Plugins and is meant to sit between your microphone and the mic preamp of your choice. A logic circuit ensures that only one Hi-Z input is active at a time. Read more about the HZ51X on GroupDIY.

Note:  This is a complete parts kit to build the HZ51X.  It includes full metalwork, PCB and components.  However, it does not contain any Hi-Z Plugin modules.  Plugin modules can be purchased from from CAPI here.


  • 51X or 500 series compatible (with minor modification)
  • Four plugins slots
  • Bypass for microphone
  • Output pad for loud instrument sources
  • Easily add a variety of DI inputs to any mic preamp
  • Smart input switching logic

Related Products