The 5021 from TL Audio is a two channel, dual tube compressor with noise gate and variable controls. In addition to the normal connectors, the unit also provides front panel instrument inputs that allow guitars, basses and keyboards to feed directly into it, removing the need for a separate DI box. Two illuminated VU meters monitor the output level or the gain reduction.
A solid state, electronically balanced input amplifier is used to achieve very low noise, low distortion and wide bandwidth performance. An ECC83/12AX7A triode valve stage, run from a stabilized 150V DC supply, is used as a second stage voltage amplifier to obtain the classic valve sound and gradual overdrive characteristics. A second ECC83 valve stage forms part of the compressor gain make-up circuit.
Compressor sidechain connectors on the rear of the 5021 can be used to connect an external processor such as an equalizer into the compressor circuit, allowing the compressor to effectively become frequency conscious. A typical application of this would be to "de-ess" (remove sibilance) from a source by boosting the sibilant frequency on the side-chained equalizer.