Produced with the help of Jerry Donahue, the UK-made JD-01 adds a blend control to the DRW compressor circuitry.
This takes the place of the 4 Knob's trim knob, which is relegated to being an internal trim pot - fine if you are using the pedal with one type of guitar: just set it and forget it.
Not everyone likes their whole signal compressed, and stompbox manufacturers have picked up on this, as we are seeing more compressor pedals that allow some of the original signal to be blended in to keep some of the playing dynamics and original tone intact.
Here, with the blend control fully anti-clockwise you get only the original guitar signal, while fully clockwise only the compressed signal. Between the two lies a sweet spot where the parallel compression adds some mojo to your tone without sounding overly processed.
A versatile compressor that lets you add as much compression to your sound as you wish: well worth the extra £10 over the standard DRW 4 Knob compressor.