Manual for EC Limiter

Two band soft cross-limiter

Use it to correct/sustain/compress amplitude of both or separate low and high frequency bands of signal when one of the bands is used as an amplitude source.

Source signal splitting

The source signal is splitted into the bands of low and high frequency. All the things the limiter then do have their meaning in context of this two bands. You can change the splitting frequency with the "Spl. freq." knob.

  Though changing split frequency, say moving it down, will cause every part of source signal to have lesser or greater coefficient in the low band. Especially those with frequencies beyond split value. Thus to have usable values of the bands amplitude it's necessary to correct them. You can do it with the "Lo/Hi" knob. Detected amplitudes are shown in the indicator above it.

Amplitude detection

Only the signal of one of two bands is used as an amplitude source. You select this band with the button "Src. LF/HF".

To take an amplitude as a human ear understands it, transformed signal is low-pass filtered. Properties of this low-pass filter determines some aspects of the limiter characteristics and behavior. The filter has cutoff frequency tunable with the "A.D.F." knob. Filter order is smoothly tuned between two filters of 1-st and 4-th order with the "A.D.O." knob. Still the low order filter is less distorting amplitude, the high order filter gives harder threshold and allows to use the higher cutoff frequency. The cutoff frequency is higher, the amplitude value changes faster with signal change, the resulting sound is more responsive to actions artist. Too high cutoff frequency causes nonlinear distortion which sounds like very soft screamer.  

Amplitude correction

  The amplitude correction/sustain/compressing is provided here as multiplying by coefficient between soft-clipped then corrected to output level source amplitude and the amplitude of the signal bands, which are chosen for correction. The clipping level is tunable with the "sustain" knob, while the softness of clipping is tunable with the knob "Knee". The output level is set with the "In/Out" knob. Which bands to process - you choose it with buttons "Lim. Hi" and "Lim. Lo". In case when only one band is chosen, the other band stays untouched.  

  The standard problem/task of any limiter/compressor/sustainer is amplitude detector performance. The other thing is that while only noise presents at the limiter input, it acts like a high coefficient amplifier, because division the output level by the clipping level gives high value. It causes three similar artefact effects. The first is high amplifying of noise. You need to use any noise gate with the limiter. The second effect is that quiet sounds like touching string before attack are high amplified. The second is that the signal piece nearly after attack is high amplified too. This behavior is corrected in two ways. The first way is presented by the knobs "Attack" and "Release" which generally determine responsibility of corrected amplitude to the source signal changes. The second way is a small delay of source signal before multiplying. You tune value of this delay with the "Delay" knob.

Some special

In "www.7amp.net Experimental Combo Emulator", this limiter works in junction with "EC Distortion". The "Level" knob (I'm sorry for this name) allows to add the limited signal after the distortion output, but only the band, which is selected to be limited. You can mix distortion and clean sustained signal in any proportion.  

When neither low, nor high frequency band is selected for correcting amplitude, the limiter still does some work. If the low band is the amplitude source, then it corrects the amplitude in the high band to it. As well as reversed process. Correcting the high band amplitude to the low band makes high frequency signal components more stable as LF amplitude source is less responsive to actions of an artist. And the reversed processing allows to make them more responsive.

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