TC Electronic Broadcast 6000 - Manual (Page 150)

Brickwall 2
146 System 6000 MKII Algorithms
ting, internal variables other than Release Time
will be fixed.
Absolute Bit Transparency
Whenever the BrickWall limiter is not attenuat-
ing the signal, it is passed completely unaffect-
ed, transparent to the 24 th bit. Consequently,
the BrickWall limiter may be used to remove
0 dBFS+ peaks on already mastered and finally
dithered material. When the Limiter is bit trans-
parent, a green indicator next to the Threshold
control lights up.
Input and Output gain controls have 0.1 dB incre-
ments, but snap to bit shifts at 0, 6, 12, 18 and
24 dB settings. When a bit shift value is selected,
a green indicator is lit on the screen. Bit trans-
parency from Input to Output is obtained when
Input Gain and Output Fader hit these values and
sum to 0 dB, e.g. Input/Output 0/0 dB, -6/+6 dB,
-12/+12 dB etc.
Bit Pattern Transparency
When only bit shift gain settings are used on In-
put and Output, bit patterns remain unchanged
through the algorithm, but can be shifted up (in
the MSB direction) or down (in the LSB direction)
as desired. E.g. Input/Output +6/0 (one up), 0/-12
(two down).
Linking
The two channels BrickWall limiters can be op-
erated independently or linked. If pronounced
limiting is performed on stereo material, linking
should be considered to avoid L/R image shifts.
If only mild and occasional limiting is being done,
un-linked operation even on stereo material may
sound the best.
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 dis-
tortion. The Soft Clip threshold should be ad-
justed 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 0 dBFS+ signals, remember to
invoke the Upsample option. If only limiting ac-
tion is required, set Input Gain at 0 dB. 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 8 dB
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 compli-
ments the material. When used in combination
with the Dynamic Limiter, Soft Clip can produce
a louder and denser impression than the dynam-
ic limiter by itself. If mis-used, excessive Soft
Clip can lead to an ear fatiguing sound.
With bit transparent settings, the BrickWall lim-
iter can remove 0 dBFS+ peaks on already mas-
tered 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 Brick-
wall 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 mas-
tering, 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).