X3A Compressor

Description

X3A — Solid State Audio Leveler

The faster sibling. Same optical cell, a different amplifier, and a detector that already knows where the voice lives.

Main description

The X3A is the 1969 solid state answer to the tube leveler: the same T4B optical attenuator, driven by a transistor amplifier instead of a valve. It grabs about five times quicker and sits further forward in the midrange.

Its detector is fed from the output of the amplifier rather than the input, exactly as the hardware is wired, so the knee stays soft and the ratio rises with level instead of snapping to a fixed number. It reaches around 3.5:1 when pushed, and the knee is tighter than the X2A’s, so reduction arrives with more intent rather than fading in.

The optical cell is modelled as three parallel charge stores rather than one envelope follower. Short transients only charge the fast one; sustained material charges the slow ones too. Attack is around 2 ms, and the release stretches from about 70 ms after a quick burst to well past a hundred after heavy work.

The detector is tilted towards the presence region by about 7 dB before you touch anything. That tilt is built into the circuit rather than offered as a control, and it is why the unit ducks vocals and electric guitar the way it does. Emphasis adds up to another 12 dB on top.

The amplifier holds its line far longer than a triode and then runs out abruptly, and it is very nearly symmetric, so the third harmonic leads and the second stays out of the way. Under 0.05 % distortion at −18 dBFS. The colour lives in the iron here rather than the amplifier, and the transformer is driven harder to make up for the cleaner gain stage.

Controls

• Peak Reduction and Gain, the two knobs the original had
• Compress / Limit
• Emphasis: adds to the fixed presence tilt already in the detector, so bass drives the compression even less
• Mix: parallel blend, phase accurate
• Output trim, stereo link, external sidechain
• Meter switches between gain reduction, input and output
• Oversampling off, 2x or 4x

Specification

VST3, AU and standalone. macOS Universal (Apple Silicon and Intel), Windows 64-bit. Mono and stereo. Full plugin delay compensation, and bypass keeps the same delay so it stays aligned on a parallel path.

Reviews

Free for commercial work. Do not redistribute the installer. Licence · Piracy policy