TUBE TECH LCA-2B

The unit is all tube based (except for the power supply and side chain circuit).

The VCA (1 dual triode) is placed between the input transformer and the output stage (2 dual triodes).

The audio signal is picked up after the VCA and fed to the side chain circuit. The control signal from the compressor and from the limiter is combined and sent to the link switch and to the control amp, which feeds the VCA. The two bi-directional link busses are accessible at two 1/4" stereo jack sockets on the rear panel. The channels can be linked together for stereo applications and also linked to other LCA 2B's via the two link busses and a standard stereo jack/jack cord. 

The compressor has six att/rel presets ( Fairchild time constants ) as well as manual control. The limiter att/rel is fixed. The LED display is fed from the control amp. The limiter LED is fed from the limiter buffer.The audio path is fully symmetrical from input to output. Input and output have fully floating transformers. All DC voltages are stabilized, except the anode voltage for the output stage.

TECHNICAL FEATURES :

General                                                                                                   

• Tube VCA compressor/limiter
• All-tube based push-pull amplifier
• Frequency response @ -3 dB: 5 Hz to 50 kHz
• Low noise: < -85 dBU @ 10 dB gain
• CMRR: > 60 dB @ 10 kHz
• Separate compressor and limiter
• Output Gain: -6 dB to +10 dB
• Interconnection of several compressors via two busses
• Clickless In/Out relay
• Conductive plastic potentiometers
• Gold plated switches
• Inputs and outputs are transformer balanced and fully floating
• Linkable for stereo applications

Compressor

• Variable ratio (1.6:1 to 20:1)
• Variable threshold (Off to -20 dBU)
• Continuously variable attack and release times
• Choice between 6 presets (Fairchild) and manual attack/release control
• LED Gain reduction display

Limiter

• Variable threshold (Off to 0 dBU)
• Attack: 0.8 ms - release: 0.5 sec
• Separate Limiter On/Off switch