TK Audio BC501 Stereo Bus Compressor - 500 Series


91 out of 100. Incorporating 20+ ratings and reviews.

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TK Audio BC501 Stereo Bus Compressor - 500 Series

The BC501 is one of TK Audio's best-selling 500-series modules.

It has a combination of features that are based on the BC1-S rackmount compressor and the BC2-ME mastering compressor from the same manufacturer.

The additional features taken from the BC2-ME include ratio settings (1.25:1, 6:1), a THD switch that adds even harmonics to the signal, and three High Pass Filter settings on the sidechain (80Hz, 150Hz, 220Hz).

It makes it easy to apply parallel compression with its built-in dry/comp knob.

All of its controls are stepped for precise and easy recall. It also has an external sidechain input provided via 3.5mm TRS to connect external hardware.


  • Controls: Threshold, Ratio, Attack, Release, Make-up, Blend
  • Input/Output Impedance:24k Ohm/ 50 Ohm
  • Maximum Input Levels/Output Levels: +26dBu / +27dBu
  • Attack: 0.1, 0.3, 0.6, 1, 3, 6, 10, 30, 60, 120mS
  • Release: 50, 100, 300, 600mS, 1.2S and Auto (50mS/2S)
  • Ratio: 1:25, 1.5:1, 2:1, 4:1, 6:1, 10:1
  • Threshold: -20dB to +20dB
  • Power Requirement: +110mA / -90mA


Recording engineers and home studio owners agree this works best for mix-bus compression. They mentioned that this blends the mix like ‘glue’ while using it with low ratios and small amounts of gain reduction. In Hugh Robjohn's Sound on Sound review, it was mentioned that the compressor is generally transparent yet "the inclusion of the THD switch introduces a subtle richness, adding some interesting character, particularly on transient-rich sources." Scott Evans, a writer for, gave great comments for the BC501's design mentioning its "controls feel great, and the front panel is well- designed and easy to read." Fellow sound engineer Don Gunn mentioned he favors the compressor's variable high pass filter feature on the sidechain detector in the same review. He stated this feature "lets you set up an HPF to prevent low-frequency signals from causing the compressor circuit to over-react."


There are no consistently reported negatives, in fact Hugh Robjohn said in his Sound on Sound review, "I really can’t find anything to fault".


This versatile stereo compressor is a good choice to use for mix bus compression to 'glue' or make your mix sound cohesive.

Although this was previously on our recommended list, there are now more highly rated options available which you can see in our guide to The Best 500 Series Compressors.