Relab 176: 1960s-Style Tube Compressor Plugin by Relab Development

The Relab 176 uses four hardware ratios, 2:1, 4:1, 8:1 and 12:1. Knee position and slope change with each ratio, so the compression can range from gentle leveling to firmer limiting.

Attack and release times are not set in fixed milliseconds. The developer says they come from resistor-capacitor networks coupled to the tube gain stage, so they respond to signal level, transient size and tube nonlinearity. A Fixed/Auto toggle changes how the release adapts to the program.

The Stage Coupling switch selects between a transformer path and a resistor path. The transformer path gives faster attack, with sub-millisecond attack described as possible. The resistor path gives slower attack and a flatter tone with more low-frequency thump.

The Sidechain Polarity control changes how the detector responds to the positive, negative or both halves of the waveform. Polarity-selective detection can target specific transient edges, such as the attack of a kick drum or plosives in vocals.

Calibration shifts the internal tube bias and balance, which changes threshold, harmonic profile and dynamic feel. Clicking the Relab logo opens advanced controls: three trim pots for 6BC8 bias, 6BC8 anode balance and 12AX7 bias, plus a Reference Level control for gain staging.