glados.no/_files/sound/bss/london/manual/MAIN/MAINLeveller.htm

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<h1 class="firstHeading">Leveller</h1>
<p><font face="Arial" class="hcp1"><font size="3" class="hcp2"><img src="MAIN0126.gif" alt="MAIN0126.gif" title="MAIN0126.gif" width="137" height="51" border="0" class="hcp3"></font></font></p>
<p class="hcp4">The leveller will attempt to keep the nominal
level of the signal close to the desired target level set by the user,
by gently changing the gain. An intelligent detection algorithm makes
this processing object very free of side effects and easy to set up.</p>
<p class="hcp5"><span class="hcp6">Inputs
and Outputs</span></p>
<p class="hcp4">One audio input and one audio output.</p>
<h2 class="hcp7">Properties</h2>
<p class="hcp4"><span class="hcp6">Voice band
Filter</span>: Optionally included so that the levelling action favours
frequencies in the human vocal range, helping to discriminate from noise
signals.</p>
<p class="hcp5"><span class="hcp6">Control
Panel</span></p>
<p><font face="Arial" class="hcp1"><font size="3" class="hcp2"><span class="hcp6"><img src="MAIN0127.gif" alt="MAIN0127.gif" title="MAIN0127.gif" width="491" height="257" border="0" class="hcp3"></span></font></font></p>
<p class="hcp4"><span class="hcp6">Target Output</span>
control<br>
Adjusts the level which the leveller tries to maintain. The more positive
the value, the higher the output level will be.</p>
<p class="hcp4"><span class="hcp6">Ratio</span>
control<br>
Adjusts the aggressiveness of levelling. Lower values allow more tolerance;
allowing the output level to differ more from the target level, which
preserves more of the original dynamics of the signal at the expense of
firm control over the level. Higher ratio values cause the output level
to be more tightly 'driven' towards the target level.</p>
<p class="hcp4"><span class="hcp6">Maximum Gain</span>
control<br>
Determines how much gain the object is allowed to apply to bring a low
level signal up to the target level. Higher gain values allow the leveller
to add more gain when the signal level is low, but will also bring up
the noise floor more.</p>
<p class="hcp4"><span class="hcp6">Speed</span>
control<br>
Adjusts the time it takes for the leveller to recover from high levels
when low levels are encountered. Higher values make the recovery slower,
so there are no sudden jumps in gain. Lower (faster) values allow the
leveller to track and counteract rapidly decreasing levels.</p>
<p class="hcp4"><span class="hcp6">Bypass</span>
button<br>
Removes the leveller from the signal path.<span class="hcp6"><br>
!</span> WARNING - significant changes in signal level can be caused by
this control.</p>
<p class="hcp4"><span class="hcp6">Threshold</span>
control<br>
Determines the lowest input level that the Leveller will attempt to correct.
Correct setting of this control is critical to the leveller's ability
to discriminate unwanted noise from the wanted signal. Lower values will
allow the leveller to 'pull-up' lower level signals, but will also make
it more prone to activate on noise signals. Note that the intelligent
detection algorithm helps to prevent noise signals from triggering levelling
action even when they are above the threshold level, (if the leveller
does not recognise them as vocal signals).</p>
<p class="hcp4"><span class="hcp6">Active LED</span><br>
Shows when the intelligent detector is allowing levelling action to take
place. This is used along with the Threshold control to confirm that noise
signals do not activate the detector, but wanted signals do.</p>
<p class="hcp4"><span class="hcp6">Gain meter</span><br>
Displays how much adjustment the leveller is applying to the signal.</p>
<h2 class="hcp7">Notes</h2>
<p class="hcp4"><span class="hcp6">!</span> It
should be noted that this object is capable of raising signal levels beyond
the clipping point, so care should be exercised when using large Maximum
Gain values.</p>
<p class="hcp4"><span class="hcp6">!</span> It
is recommended that a Limiter be used on the output of the Leveller so
that short-term high-level signals (which may not be attenuated by the
Leveller), are not allowed to pass through to the output.</p>
<p style="margin-bottom: 0;"><font style="font-size: 10pt;" size="2">An
expander connected on the input side of the leveller may be useful in
aiding the leveller to discriminate noise signals from wanted signals</font></p>
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