The TUBE-TECH CL 2A is an all-tube optical compressor with two independent, linkable channels.

CL 2A is a great compressor on all sources, and it is widely known as an excellent “problem solver” when delicate gain control is called for.

Use it on keyboards, guitars, vocals or even on the mix buss – the result is always musical, smooth and transparent. Among engineers, the CL 2A is loved because of its ability to keep instruments at their right place in the mix, while still retaining their dynamics.


Features and Technical Specifications

CL 2A is a two channel all-tube opto compressor, featuring two independent channels. The optical gain reduction element is placed after the input transformer and followed by an all tube-based output amplifier with a +10 dB gain.

A link switch is provided for use of the two separate compressors in stereo mode or for linking several compressors together.  Both Input and Output are balanced and have fully floating transformers with a static screen.

The power supply and the sidechain circuit are based on solid state designs. With the exception of the anode voltage for the output stage, all DC voltages are stabilized.

  • Low-distortion optical gain reduction element
  • All-tube based push-pull amplifier
  • Frequency response @ -3 dB: 5 Hz to 60 kHz
  • Low noise: < -80 dBU @ 10 dB gain
  • CMRR: > 60 dB @ 10 kHz
  • Variable ratio from 1.5:1 to 10:1
  • Continuously variable attack and release times
  • Output gain: Off to +10 dBU
  • Variable threshold: Off to -20 dBU
  • VU meters show output or compression
  • Linkable for stereo applications
  • Interconnection of several compressors via two busses
  • Clickless In/Out relay
  • Conductive plastic potentiometers
  • Gold plated switches
  • Input and output are transformer balanced and fully floating


Sound Examples


Female Vocal (bypass)

Female Vocal (CL 2A)



Male Vocal (bypass)

Male Vocal (CL 2A)



Guitar (bypass)

Guitar (CL 2A)



Bass A (bypass)

Bass A (CL 2A)



Bass B (bypass)

Bass B (CL 2A)



Snare A (bypass)

Snare A (CL 2A)



Snare B (bypass)

Snare B (CL 2A)


FAQ: What’s the difference between CL1B and CL2A?

The TUBE-TECH CL2A design is based on the famous CL1B but not exactly the same.

  • CL2A versus CL1B: CL2A is based on the CL1B, but it”s not a stereo CL1B!
  • Some differences exist between the two units: CL2A features a different optical element, with a little more “soft”or “rounded” action compared to the element in the CL1B.
  • The amount of transparency you get when using the CL2A is similar to the CL1B.
  • The tube amplifier circuit is basically the same, with the main difference being that the input transformer and the tube amps in the CL2A delivers a more “normal” amount of gain compared to the CL1B
  • The control circuit has been changed so the CL2A”s max release time is two seconds.

GearSlutz Thread about the differences between CL1B and CL2A



Tech Spec Sheet
Recall Sheet

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