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Soft Clip
Soft Clip is a bandwidth limited distortion effect, not unlike
analog tape saturation. Soft Clipping can add loudness to
a signal at the price of distortion. The Soft Clip threshold
should be adjusted so only the peak content of the signal is
affected, not the average part.
Because of the double precision calculations used in
the algorithm, pre-limiter signal level and the Soft Clip
Threshold may exceed 0 dBFS. The Left and Right Soft
Clippers always operate un-linked.
Operational Hints
Normal operating procedures involve first setting the
Limiter Threshold at the desired maximum Output level. If
you want to protect downstream equipment from 0dBFS+
signals, remember to invoke the Upsample option. If only
limiting action is required, set Input Gain at 0dB. To add
loudness without raising the peak content of the signal, use
the Input Gain as a drive control like on analog Limiters.
Use the Gain Reduction meters and your ears as
guidelines to when it is time to stop adding more gain. For
not previously limited or compressed signals, as a rule of
thumb, don’t exceed 8dB of gain reduction if not for artistic
reasons. If the signal is already heavily dynamic range
reduced, less drastic limiting treatment is indicated.
Experiment with different Auto Release and Soft Clip
settings to find the type that best compliments the material.
When used in combination with the Dynamic Limiter, Soft
Clip can produce a louder and denser impression than the
dynamic limiter by itself. If mis-used, excessive Soft Clip
can lead to an ear fatiguing sound.
With bit transparent settings, the BrickWall limiter
can remove 0dBFS+ peaks on already mastered and
finally dithered material. Under such conditions, it is not
necessary to apply dither to the signal again.
What goes in goes cloned to the output, as long as the
input stays below the threshold of limiting. This can be
guaranteed because the architecture of System 6000 is
designed that way, and Brickwall 2 doesn’t rely on a work
station program or a computer OS to keep its fingers off
the audio.
Examples of Brickwall 2 presets for CD mastering,
broadcast and post production can be found in Engine
Factory Bank 10, decade 2.
Look-ahead Delay (Latency)
To control peaks more precisely and minimize transient
distortion, Brickwall 2 inserts a short delay into the
signalpath. The delay amounts to approximately 0.8 ms at
all sample rates: 37 samples at 44.1 kHz, 39 samples at 48
kHz, 64 samples at 88.2 kHz and 69 samples at 96 kHz.
(Delay times given reflect Engine in to Engine out, and
therefore excludes delay in I/O circuitry such as AD and
DA converters).
More information
About 0dBFS+ signals, required headroom in the
signalpath, behavior of consumer CD players and
production equipment can be found at the TC website, from
which technical papers about related issues also can be
downloaded.
Main Page
Input Gain Left and Right
Range: +/-24dB
Overall Gain/Drive control at the input of the limiter. Once
the threshold has been set, this is a convenient place to
adjust more or less dynamics processing and loudness.
The Gain parameter offers the same “Drive” approach to
level and threshold used in classic analog limiters. Unlike
analog designs, however, Brickwall 2’s 48 bit internal
resolution prevents resolution and signal/noise ratio from
being sacrificed, because the processing dynamic range is
larger than even the highest resolution input would be.
If bit transparency and/or conservation of bit
patterns are of essence, note the green indicators
above the Gain controls. When they are lit, bit shifts
are used for gain control rather than rounded
calculations where bit patterns are re-shuffled. For
instance, if a 1 bit shift up is used as Gain (+ 6.0
dB), the antidote 1 shift down (-6.0 dB) can be used
at the output Fader to assure 24 bit transparency,
when the signal is below the threshold of limiting.
If the Fader instead remains at 0.0 dB, the input bit
pattern is still preserved, but the bits are shifted one
position towards MSB.
Green Input Gain LED indicator
Indicates bit transparency (read introduction for details).
Link
Press to Link L and R Gain controls and the sidechains.
Note that phase and delay controls work independently of
this setting. If the limiting threshold is frequently hit with
music, link the channels to stabilize the stereo image. For
dialog or un-correlated instruments, best results may be
obtained by keeping the channels un-linked.
