The SSL Bus+ (styled THE BUS+ by Solid State Logic) is a 2U, 19-inch analogue stereo bus compressor. It builds on the centre-section compressor found in SSL consoles since the 4000B of 1976, adding new compression colours, extra modes, a two-band dynamic EQ and more processing tools. It is designed for mix-bus and mastering work, and for bus and parallel compression on sources such as drums, piano, acoustic guitars and strings.
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Classic SSL circuit: a 100% analogue signal path with THAT 2181 VCAs and moving-coil gain reduction meters
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Four modes: Classic Stereo, Σ S/C Stereo, Dual Mono and Mid-Side
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Three combinable colours: LOW THD, F/B feedback side-chain and 4K MODE
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D-EQ: a two-band analogue parallel dynamic EQ that can compress or expand, placed before or after the compressor
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Stepped, recallable controls: front-panel pots are read by a microcontroller, which avoids pot tolerances and makes settings easy to recall
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Parallel and side-chain tools: MIX control, external side-chain inputs and sends, and a 12 dB/oct side-chain HPF
The compression colours change how the unit behaves. LOW THD alters the side-chain to reduce the low-frequency distortion that compression introduces, which is most noticeable at fast release times. F/B takes the side-chain signal from after the gain-reduction VCA for a more relaxed response, and 4K MODE runs the VCA unbalanced, as in 4000-series consoles, with an adjustable amount of harmonic distortion. The three can be used together.
Compared with earlier SSL bus compressors, the timing options are wider. Attack runs from 0.1 to 40 ms and adds 6, 15, 20 and 40 ms settings, while release covers 0.05 to 1.2 s with both the classic AUTO and a new Auto 2 setting. The ratio control ends in three negative positions, useful for pumping effects or for controlling very loud material. Make-up gain is MDAC-controlled in 1 dB or 0.5 dB steps.
The D-EQ is SSL's first dynamic EQ. Each band has 16 frequency points, three time-constant options (Nominal, FAST, AUTO) and a range from 0.5 to 15 dB. The HF band switches between shelf and bell, and G-Series mode gives the LF filter a second-order response with some undershoot and overshoot. The external side-chain can drive the compressor, the D-EQ or both.
Further details include +27.5 dBu headroom, selectable operating levels of 0, +10 and -5 dB, per-channel bypass buttons, Sleep and Auto-Sleep modes, and a Transient Expander that is unlocked by beating a code-breaking game built into the unit.