TK Audio BC1-THD


TK Audio BC1-THD

Smooth transparent glue.

  • Sidechain filter with three frequencies.
  • Selectable THD function for more “even” harmonics.
  • Grab function that selects a harder threshold knee.
  • Blend control for easy parallel compression.
  • All controls stepped for easy recall.

Engineers call it “The Magic Glue” when the BC1-THD’s transparent compression strengthens mixes without compromising clarity. The BC1-THD provides smooth bus compression that applies for both mixing and tracking. The built-in blend control makes it easy to apply parallel compression by adjusting the blend of dry and compressed signal. A switchable sidechain filter can be applied which makes the BC1-THD less responsive to low frequency energy. The THD function adds more harmonics to the signal and the “grab” mode selects a harder threshold knee on all four ratio settings. Smooth and transparent compression will never go out of fashion.

  • Frequency response: 20Hz to 20kHz less than -0.025dB
  • Frequency response: 20Hz to 80kHz less than -0.3dB
  • THD+N @ 0dBu: less than 0.0045%
  • Input impedance: 20kohm
  • Output impedance: 50ohm
  • Max input level: +26dBu
  • Max output level: +27dBu @ 600ohms load

BC1 Version History

  • BC1. Release October 2008
  • BC1mk2. Higher internal voltage, updated signal path for lower noise, internal jumpers for unbalanced use to add 6dB output gain. (released in October 2011)
  • BC1-S. New output stage, stepped potentiometers for Threshold, Make-up and Blend. (released in April 2013)
  • BC1-LTD. 10 year anniversary version, individually numbered on front panel, silver panel. Three HPF frequencies, THD function and Grab function (harder knee)
  • BC1-THD. As above version with standard black panel


  • Threshold: -20dB to +20dB
  • External sidechain: in/out
  • Ratio: 1.5:1 / 2:1 / 4:1 / 10:1
  • HP Filter: 80Hz, 150Hz, 220Hz, -6dB octave
  • THD: adds more even harmonics
  • Grab: selects a harder threshold knee
  • Attack: 0.1/0.3/0.6/1/3/6/10/30/60/120mS
  • Release: 50mS/100mS/300mS/600mS/1.2S/Auto
  • Gain reduction meter
  • Make-up: 0 to +20dB
  • Dry signal mute
  • Blend control: from dry to compressed
  • Compression in/out
  • External sidechain input: unbalanced TRS jacks
  • Internal, regulated power supply with a toroidal transformer
  • 115 or 230V, selectable

Specifications and components may be changed or updated without further notice.