TK Audio BC1 MkII Stereo Compressor / Limiter


TK Audio BC1 MkII Stereo Compressor / Limiter, 1U rack, SSL-style bus compressor

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The TK Audio BC1 MkII is one of the many takes on the SSL buss compressor concept. The original SSL Quad Buss compressor was across the output busses of the SSL 4000E. If you knew your way around the patchbay, the rear channels allowed the compressor to be keyed by the back busses, but most used the compressor the same way – hit the On button, 4:1 ratio, slowish attack and tickle the compressor by a couple of dB. Used that way, the compressor gave a tight, punchy result that suited the overall sound of the console. You’ll have heard the sound – over half the hit records in the last thirty years used the SSL buss compressor

The SSL compressor became a product in its own right in a 1U rackmount box, in the original version with dbx VCAs then in the current Superanalogue version. Alan Smart, ex-SSL installation & development engineer, produced his versions of it and there are numerous other versions, homages, reinterpretations and clones

TK Audio has taken the super-clean route with the BC1. It uses the famously-transparent VCA chips from THAT Corporation and adds lots of flexibility with multiple compression ratios and sidechain manipulation. SSL uses 4:1 as the lowest ratio, but TK starts with 1.5:1, and offers 1.5:1, 2:1, 4:1, 10:1 and Hard to give a greater range of effects

The BC1 mixes the dry (uncompressed) and compressed signals via a Blend control to give variable parallel compression. This technique is used by many of the top mix engineers to get just the right balance of smoothness and punch in a final mix. Having the blend adjustable on the front panel – and a mute button for the dry signal – transforms the BC1 into a proper mixing tool

TK Audio describe the BC1 as providing the “Magic Glue” for mixes. I know what they mean – once you start balancing mixes with a buss compressor, it becomes easier to pull the balance together to make a cohesive mix. Even at low compression ratios, buss compression pulls up details that can get hidden in busy mixes and, by working the compressor harder and changing the dry/compressed blend, it’s possible to make the mix punch hard without becoming obnoxiously compressed

Key features

  • Smooth VCA buss compression
  • “Magic Glue” effect on mixes
  • Dry / Compressed blend control for parallel compression
  • Straight signal mute button
  • Super-clean THAT VA chips
  • Extended ratio, attack and release controls
  • External sidechain input with switchable high-pass filter
  • Single or dual side-chain detectors

The BC1 takes the SSL buss compressor idea to a new level.  Using the highest-quality VCAs ensure the signal remains clean, but the real cleverness is in the sidechain.The sidechain defines how the compressor will respond, and TK adds flexibility here with an external input, two detector setups and a high-pass filter to avoid the bass pumping the mix excessively. In an ideal world you’d have one of these, an original SSL compressor with “Gold Can” dbx VCAs and an Al Smart C2 but, if you can only have one, I recommend the TK BC1

Inputs & outputs are on XLR connectors and the external key input uses a jack socket.  Mains input is a standard IEC mains socket and there's a 120 / 240 voltage selector on the side of the unit.  IEC mains cable not supplied but I am happy to include one if required
Standard 19" 1U device suitable for all 19" racks.  120 / 240 Volt switchable with a standard IEC input.  Mains cable not supplied but I am happy to include one if required
Product page (related BC-1S)
Owners manual
Sound on Sound Review
Gearslutz Review

In excellent condition, like new.  No rack rash or marks on the front panel, case looks like new