OPTO Stereo Compressor


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The Alice 538R is a full size mains powered 1U rackmounted version of our popular 538T OPTO stereo compressor from the 500 Lunchbox series.

The 538R has OEP transformer balanced inputs and outputs, a side-chain input and dual VU meters.

Ted Fletcher’s historic opto compression design
Perfect ‘Hard-Wired’ by-pass for instant comparisons
Wide range ratios from gentle to brutal
Accurate UV compression metering on a real meter
Extreme stereo width control
Shielded hand-matched audio transformers
The ‘538R’ is designed for creative compression effects that are difficult to achieve with plug-ins. It’s capable of extreme compression just as Ted Fletcher’s original Joe Meek SC2 V5; amazing drum sounds! It’s also super-quality ‘Levelling Amplifier’ with the sparkle of a well-designed opto compressor.

The 538R is a 1U rackmounted unit using mains voltage.

Inputs & Outputs
Left and Right transformer balanced inputs and outputs are via hand matched OEP canned transformers

Side-chain via a 6.35mm stereo TRS connector

Width Control
In order to retain perfect symmetry between the left and right channels of the stereo equaliser the audio signal is processed into ‘sum and difference’ mode (that is L+R = ‘sum’, L-R = ’difference’), the two audio signals are then processed by the EQ controls before being re-processed back into left and right format. By going through this process the left and right channels remain perfectly symmetrical with no image shift, any minor difference between the processed sum and difference signals show up only as small deviations in width of the stereo image. A further useful advantage of the sum and difference processing is that the width of the stereo image is controlled by the volume level of the ‘difference’ channel so by adding a gain control the stereo width can be accurately controlled. With the width control at minimum the audio output is mono. When the control is half way, the processing accurately recombines the audio into left and right. If the control is increased further, the image is extended beyond the original stereo.

Easy-to-read stereo analogue meters reading audio (UV) or compression depth (comp)