Tube-Tech LCA 2B Dual Channel Tube VCA Compressor

The Tube-Tech LCA 2B is one of the most powerful and adaptable VCA compressors available, designed with versatility in mind. It performs exceptionally well across a variety of applications, from vocals and instruments to bus compression, making it a truly universal tool.

With a quick and smooth attack, it is especially suited for dynamic sources like drums and percussion, delivering punchy results that bring out the energy of the performance.

The Tube-Tech LCA 2B handles nearly any compression task effortlessly. It’s an ideal choice for bus compression, whether used inserted directly or in parallel, where it provides a rich and powerful tone. For single instruments and vocal tracks, it offers precise control that’s easy to dial in, with a clear, musical action that makes finding the perfect setting straightforward.

Designed with the legendary Fairchild 670 in mind, the Tube-Tech LCA 2B emulates the compression characteristics of this classic unit without duplicating its circuitry.

While it shares the Fairchild’s signature behaviour, it retains transparency and preserves high frequencies even under heavy compression. The fixed attack and release constants match those of the Fairchild, delivering familiar and highly musical response curves that engineers love.

If you’re seeking even greater control, power, and intensity than the iconic Tube-Tech CL1B can provide, the Tube-Tech LCA 2B is an excellent choice. Its robust construction and reliable performance have made it a staple in the touring racks of top live sound engineers and a valued tool in high-end studio environments.

The Tube-Tech LCA 2B is a dual-channel unit, featuring a separate compressor and limiter for each channel. Built on an all-tube design (with the exception of the power supply and sidechain circuit), it uses a dual-triode tube as the VCA, positioned between the input transformer and output stage, which uses two additional dual triodes.

The signal is tapped after the VCA and routed to the sidechain circuit, where the compressor and limiter control signals are combined, sent to the link switch, and then to the control amplifier, which modulates the VCA. Two bidirectional link buses are accessible via 1/4″ stereo jacks on the back panel, allowing channels to be linked for stereo operation or for integration with other Tube-Tech LCA 2B units using standard stereo jack cables.

The compressor offers six attack/release presets (matching the Fairchild’s time constants) as well as manual control options, while the limiter’s attack and release settings are fixed. An LED display, powered by the control amplifier, provides gain reduction monitoring, and a separate LED shows limiter activity, fed from the limiter buffer.

The audio path is fully symmetrical from input to output, with fully floating transformers on both input and output, ensuring clean, balanced signal flow. All DC voltages in the unit are stabilised, with the exception of the anode voltage for the output stage, delivering consistent performance and sound quality across a range of applications.

Tube-Tech LCA 2B Tube Compressor Calibration
Like any other compressor, that uses tubes for the VCA, LCA2B occasionally needs calibration. We recommend that the unit should be calibrated at least once a year. In real life, depending on the compression tube (ECC81) the LCA2B will often work perfect for a much longer period of time.

A quick test will tell you if calibration needed:

• Turn the THRESHOLD for both compressor and limiter fully CCW.
• Connect a 1kHz tone at a level of 0 dBU (-4VU) to the input and turn the LIMITER THRESHOLD
  slowly CW until the LIM led (RED) turns slightly on.
• If the LIM led (RED) turns on abruptly or even starts oscillating, the balance should be calibrated.

This test can also be done with audio: If the LCA2B needs calibration, the compressor starts pumping with this extreme setting.