A complete channel strip built from circuit models: a five-band parametric EQ with a full VCA dynamics row — noise gate, downward expander and a soft-knee compressor/limiter — plus an opto input limiter in front of it all. Free download.
Every section is a component-level model of a real analogue circuit, solved from the schematic: the EQ filters are computed node by node, the compressor's soft knee falls out of a diode's exponential I/V characteristic sitting in its control path, and the gate closes with a constant-slope ramp because that is exactly what a constant current source pulling on a timing capacitor does. Turning a knob does not switch a digital filter; it moves the potentiometer inside the simulated circuit. Where analogue behaviour has a shape, that shape is in the model — not drawn in afterwards.
A comparator gate, not a soft one: opens near-instantly so transients never get clipped, holds open for 0–2 s with retrigger, then closes with a constant-rate ramp of 10–500 dB/s. Threshold −25…+5 dBu, sidechain key input, MIX as gate depth.
The compressor circuit with its control path mirrored — below the threshold the gain falls away with the same soft knee. Ratio 1:1…1:3.94, RANGE caps the floor at 0–60 dB. For bleed and hiss without chopping decay tails.
Each band sweeps 10 Hz–21 kHz in three ranges (×0.1 / ×1 / ×10), gain ±18 dB, FRQ/WIDE bandwidth. State-variable filters with centre-tapped gain pots — the airy top end of the real hardware. Sweepable HP 10–250 Hz and LP 3–41 kHz.
RMS-detected, feed-forward VCA compressor with a genuinely soft knee and the fixed, program-friendly time behaviour of its analogue control path. Ratios 1:1 to a 51:1 brick, ±18.5 dB make-up, sidechain, MIX for parallel compression.
GAIN ±20 dB and a Vactrol limiter with CEIL −24…0 dBFS in front of the whole chain, catching peaks before the strip sees them — timing from the VTL5C3 datasheet.
Below 100 % the dry signal dilutes the processed one: for the gate that is the depth of the cut, for the expander the floor, for the compressor plain parallel compression. Gate, expander and compressor are each switchable OFF / PRE / POST the EQ.
Two channels from one set of controls with LINK, or dual mono — switch the panel to L or R and edit each side on its own. The whole path runs in an oversampled block (1× / 2× / 4×) so fast gain changes don't fold back into the audible band.
A 19″ 2U drawing, screen-printed like the real thing; everything that moves is drawn live over it. Hover to read a value, double-click to reset, SCALE 1–5 picks the window size. Portable presets hold the whole strip.
Linux: unzip into ~/.clap/ or ~/.vst3/.
Windows: into %COMMONPROGRAMFILES%\CLAP\ or %COMMONPROGRAMFILES%\VST3\.
Then rescan plugins. Tested in Bitwig, Ableton Live and Cubase. GPL-3.0 — free and open source.
Every control, its range and what the circuit behind it does — input stage, gate, expander, EQ, compressor, presets and the signal path. Download the PDF.
The PEQ15 equaliser and the AKL 634 / 636 dynamics were published as DIY studio constructions by Alan Kraus in Amatérské radio (2001–2006). LAP PEQ15 models the complete instruments from their schematics; stereo is two of them side by side.
In the works. More when it's ready.
In the works. More when it's ready.