Whistle Rock Audio HZ51x DI

Projects > Whistle Rock Audio HZ51x DI

The HZ51x is a DI for the 500-series/51x Alliance that adds an instrument input to any 500-series/51x microphone preamp. It uses the Hi-Z plugin format to offer four different tonal options through four individual 1/4″ inputs. Only one input can be used at a time. The Hi-Z DI plugins are the same as found on the ClassicAPI 312DI, and are available through ClassicAPI.

Images courtesy of Whistle Rock Audio

Notable Features:

  • Adds DI capability to any mic preamp
  • Four HI-Z plugin options:
    • HiZ-TX1: Uses a Jensen or Cinemag transformer
    • HiZ-TX2: Pikatron transformer
    • HiZ-FET1: FET DI
    • HiZ-IC1: Based around an OPA2604 opamp
  • Can run on either +/-16v (500-series) or +/-24v (51x Alliance)
  • Output pad
  • DI bypass switch (mic input selector)


  • $120 for the basic kit
  • $35 for faceplate from Front Panel Express
  • $58 for all four Hi-Z plugin kits
  • $52 for Cinemag transformer for the HiZ-TX1 plugin

More info:

  • More about the DI (including its suspenseful debut) here.
  • Preorders taken here.