LAP TSL-K35
A compressor-expander built as an automatic level controller: a FET gain cell steered by a control voltage, with the amplifiers and the relay around it, modelled part by part and solved as a circuit in real time. Two independent sections - a compressor that works around a fixed rotation point instead of a threshold, and an expander that pushes down the noise in the pauses.
What it is. TSL-K35 is a compressor-expander built as an automatic level controller: a FET gain cell steered by a control voltage, with the amplifiers and the relay around it, modelled part by part and solved as a circuit in real time. It has two independent sections. The compressor (GAIN, RATIO, RELEASE, AUTO) evens out the level of the programme around a fixed reference point. The expander (THRESHOLD, EXP) pushes down whatever falls below its threshold - noise, spill and room sound in the pauses. THRESHOLD belongs to the expander only; the compressor has no threshold. What the compressor does. Instead of a threshold it has a rotation point, 0 dB = −12 dBFS, through which every curve passes. Above it the signal is compressed by RATIO (2:1 … 20:1); below it quiet material is lifted towards the rotation point by the same ratio, but never by more than GAIN - so GAIN is not a make-up control but the most the unit may add to quiet passages. What the expander does. Below THRESHOLD (−55 … −15 dB relative to the rotation point, i.e. −67 … −27 dBFS) it lowers the gain 1:2, so a signal 10 dB under the threshold leaves 20 dB under it. The REGULATION meter shows the gain the unit is applying right now.
A rotation point, not a threshold
The compressor has no threshold. Every curve passes through a fixed rotation point, 0 dB = −12 dBFS: a signal at −12 dBFS leaves at −12 dBFS whatever RATIO and GAIN are set to. Above it the signal is compressed by RATIO, below it quiet material is lifted towards it by the same ratio - but never by more than GAIN.
GAIN is a limit, not make-up
GAIN is the most the unit may add to quiet passages. At 0 dB it only compresses, and only above −12 dBFS - a classic peak tamer. At +18 dB with RATIO 20:1 it holds everything from about −32 dBFS to full scale close to −12 dBFS - an automatic level controller. Turning GAIN or RATIO takes effect at once.
RELEASE · AUTO
The detector follows the peaks of the input with a fixed, fast attack (under 1 ms). RELEASE sets the recovery, 0.5 - 3 s. AUTO makes it programme-dependent: the recovery is extended by how long the input stayed above the rotation point, up to about 10 s - short peaks come back quickly, long loud passages slowly and without breathing.
Expander
With GAIN turned up the compressor lifts the noise in the pauses as well. Below THRESHOLD (−55 … −15 dB relative to the rotation point) the expander lowers the gain 1:2 - set low it cleans the pauses, set high it tightens the room between drum hits. THRESHOLD belongs to the expander only; with EXP off it does nothing.
REGULATION · COMP · POWER
The meter shows the gain the unit is applying right now: LIFT to the left, 0 at the rotation point, CUT to the right. COMP takes the compressor out of the path through the relay of the unit; POWER switches it off. A stereo track gets two units with one common sidechain, so the image stays in place.
Output transformer · SATURATION
After the unit can sit a model of a real audio output transformer - the core with its magnetisation and hysteresis solved sample by sample - for weight in the low end and low-order harmonics that grow with the bass and the level. SATURATION drives it from −12 to +18 dB without changing the level. Off by default - switch TRAFO ON in the settings menu.
Settings menu
Right-click the panel: window SCALE 80 / 100 %, OVERSAMPLING 1x / 2x / 4x, TRAFO OFF / ON and SATURATION. Everything can be changed while playing - a new pair of units is built in the background and cross-faded in, without a drop-out.
Presets
A preset bar above the panel: categories, Save / Save as / Delete and ◀ ▶ to step through the settings. A preset holds the knobs, AUTO, EXP and the menu settings; the selected preset is saved with the project. One plain file per preset - copy them between machines and systems.
A mastering plugin
The audio board is solved as a circuit at every sample: about 35 % of a CPU core for a stereo instance at the default 2x oversampling (about 20 % at 1x, 65 % at 4x), the same in 96 and 192 kHz sessions. Made for the master bus, stems and a few key tracks - not for every track of a session.
First release. GAIN 0 … +18 dB, RATIO 2:1 … 20:1, RELEASE 0.5 … 3 s, AUTO (programme-dependent release), expander with THRESHOLD −55 … −15 dB and EXP, COMP and POWER, the REGULATION meter; oversampling 1x / 2x / 4x (default 2x); a model of a real audio output transformer (off by default) with SATURATION −12 … +18 dB; presets that include the right-click menu settings and are saved with the project.