Drip Electronics 175 VariMu Compressor

Projects > Drip Electronics 175 VariMu Compressor

The Drip 175 is an exact recreation of the Urei/Universal Audio 175b vari-MU limiter.  Drip Electronics offers a PCB and support for this project. Since the 175 shares the same vari-MU compression style as the Fairchild 660/670, Drip has also developed an add-on which allows the 175 to emulate the Fairchild time constants.

Notable Features:

  • Tubes used:
    • 6bc8
    • 12bh7
    • 12ax7
    • 6aL5
    • ob2 regulator glow tube
    • gz34 rectifier tube
  • PCB accepts metal film or carbon comp resistors
  • Retains original power supply
  • Directly accepts PCB-mount transformers from:
    • Sowter
    • Hammond
    • Cinemag
    • Lundahl
  • Employs a ground plane
  • Optional Fairchild time constant add on

Features of the 660 Time Constant:

  • Six preset time curves
  • Fully assembled
  • Option for Grayhill rotary switch


  • $100 for PCB
  • $75 for Fairchild 660 Time Constant or $100 for Grayhill model

More information: