Jürgen Haible’s ELOC is a DIY optical compressor, based on Urei/Teletronix LA-2A and LA-3A designs. Haible’s design departs for these classic circuits in that it does not incorporate a negative feedback loop. According to the builder, this modification gave the compressor “a wonderful soft clipping,” and increased the harmonic distortion imparted during linear (non-clipping) operation. Haible’s website has schematics, pictures, and build notes for curious and ambitious DIYers.

Images courtesy of Jürgen Haible

Notable Features:

• Based on the classic Urei LA-series optical compressors
• No feedback loop
• 12AX7 and 12BH7 vacuum tubes
• OEP and Lundahl transformers

Price: True DIY! (no products available)

More information at JH’s personal website.