Creative Emu 1820m Manual

							5 - Effects
Core Effects Descriptions
E-MU Digital Audio System81
Parameters
Threshold
When the input signal rises above the level set by the Threshold parameter, the Gate is 
triggered to turn on and go from its maximum gain reduction level up to 0dB gain. The 
turn-on threshold is adjustable anywhere between -70dB and 0dB (below the PatchMix 
nominal operating point of -12dBFS.)
One of the keys to the smooth operation of the Gate is that the input Threshold level 
that turns on the Gate is always higher than the level that shuts off the gate. This means 
that the input signal level must descend substantially below the Threshold in order 
to turn off again.
This difference between turn-on and shut-off levels, or the hysteresis, is 10dB. That 
means that if the Threshold is -30dB, the signal level must fall to -40dB before the Gate 
will begin to shut off. 
Release Time
This parameter controls the time, in milliseconds, that is required for the Gate to shut 
off. More specifically, this is the time that will be required for the Gate control signal to 
go from unity gain at 0dB down to the Max Gain Reduction level.
The optimum value for the Release time is dependent on the program material as well 
as the effect youre trying to achieve. Optimum Release time is also highly dependent 
upon the settings of the Threshold and Max Gain Reduction parameters.
In general, times less than about 10 msec are prone to cause clicks in the output, while 
times longer than 30 msec may make the gating effect obvious if the background signal 
being gated out is very noisy.
Max Gain Reduction
This parameter sets the attenuation that will be applied to the signal when the Gate is 
shut off. The Gate control signal will swing between 0dB and this value as the Gate turns 
on and shuts off.
To perform a strict “gating” operation, Max Gain Reduction would normally be set to -
infinity in order to completely silence the output of the Gate.
However, there are good reasons to set Max Gain Reduction to something less drastic 
than infinite attenuation. Sometimes the silence between gated signals is “too quiet” - 
especially when the signal represents a solo vocal or instrument, where the complete 
lack of any sound between voiced segments sounds unnatural. For these applications, 
setting Max Gain Reduction somewhere between -20dB and -40dB is more appropriate.
In tandem with a high Threshold, Max Gain Reduction can also be set to very modest 
values like -5 or -10dB in order to add a subtle “punch” enhancement to transients. This 
has an effect similar to an expander, where the attack transients which exceed the 
Threshold stand out by 5 or 10dB above the normal signal (you can make up for that 5 
or 10dB attenuation by using a trim pot or boosting the channel strip gain after the 
Gate.)
Lookahead
By default, the Gate effect uses a fixed 1 millisecond lookahead to avoid clipping off the 
leading edge of signal transients when the Gate turns on. However, this is actually 
implemented by adding a 1 millisecond delay to the signal through the gate. For appli-
cations where this additional 1 millisecond latency is a problem, the Lookahead can be 
turned Off. 
						

							5 - Effects
Core Effects Descriptions
82Creative Professional
Level Meter
This meter represents the input signal level in dB, and is in fact the output of the Gates 
envelope follower. Since the envelope follower is driven by the greater of the left or right 
channel, this monophonic meter represents the greater of the two input signals.
Gain Reduction Meter
This meter shows the value in dB of the gate control signal which is used to boost or 
attenuate the input signal. Its most-rightward maximum value of 0dB represents a unity 
gain path through the Gate in its turn-on state. Except for the possibility of the 1 milli-
second lookahead latency, the Gate behaves exactly as a straight wire in this turned-on 
state. Values less than 0dB represent the amount by which the input signal is being 
attenuated as the Gate shuts off.
The most-leftward gain shutoff value achieved by the Gain meter is set by the Max Gain 
Reduction parameter (values from -70dB to -infinity are off the meter.) The speed with 
which the Gain signal decays from 0dB to the shutoff value can be observed to change 
according to the Release time parameter. 
						

							5 - Effects
Core Effects Descriptions
E-MU Digital Audio System83
Reshaper
The Reshaper effect is a special purpose dynamics modification program, designed to 
“resculpt” the amplitude envelope of an audio signal. The effect uses an envelope 
follower and threshold detector to drive an ADSR-type gain stage, which can impose 
new attack, decay, sustain and release profiles on the signals original envelope.
Applications
•“Punch” Reducer - slow turn-on with added lookahead trims attacks off signals
•“Punch” Enhancement - fast turn on with high thresholds and release gain 
expands signal attack transients
•Auto Volume Pedal - long attack times with Attack Retrigger can automatically 
simulate use of a guitar volume pedal for gently fading in each note.
•Ambience Reduction - can be used like a gate to suppress ambient reverberations 
that below a certain threshold.
When the input signal exceeds an adjustable Threshold, the Attack phase begins and 
continues until the gain reaches unity (0dB). After the Attack peaks, the gain stage 
immediately transitions into the Decay phase, which continues until the gain falls to the 
Sustain level. During the Sustain phase, the gain stage holds a constant level until the 
input signal passes below the Release Threshold. During the Release Phase, the gain 
returns to the Release Level where it remains until the another input transient triggers 
the next Attack phase.
Threshold
Release Threshold0 dB
Release
Level Sustain
Level
Attack
TimeDecay
TimeHold
TimeRelease
Time 0 dB
Original
Waveform
Reshaped
Waveform 
						

							5 - Effects
Core Effects Descriptions
84Creative Professional
Attack, Decay and Release times are all adjustable, and the shape of each of these 
segments is selectable between exponential, linear, or logarithmic. An additional Hold 
Time can be used to extend the Sustain phase past the point where the signal has passed 
the Release Threshold.
If the Sustain Level is set the same as the Release Level, then the Reshaper effectively 
becomes a two-phase “transient catcher” where the Release Threshold, Hold Time and 
Release Time are ignored.
While the peak Attack gain level is always fully turned on, note that the Release Level is 
not necessarily completely off, but can be adjusted upward so that the Reshaper retains 
a nominal minimum gain. This allows the Reshaper to resculpt only the louder 
transients of a signal while maintain a nominal output signal level the rest of the time.
The Release Threshold is always expressed relative to the Attack Threshold so that they 
will automatically track each other when the Attack Threshold is adjusted.
Parameter Description
Attack ThresholdWhen the input signal rises above the level set by the Attack Threshold 
parameter, Reshapers ADSR engine begins the Attack phase. The turn-
on threshold is adjustable anywhere between 
-40dB and 0dB (below the PatchMix nominal operating point of 
-12dBFS.)
Attack TimeThis parameter controls the time, in milliseconds, that is required during 
the Attack phase for the gain rise from its quiescent Release Level to 
unity gain, or 0dB.
Decay TimeThis parameter controls the time, in milliseconds, that is required for the 
gain to fall from 0dB down to the attenuated Sustain Level. Note that if 
the Sustain Level is set to 0dB this decay time becomes simply a delay 
before entering the Sustain phase.
Release TimeThis parameter controls the time, in milliseconds, that is required for the 
gain to fall from the Sustain Level down to the Release Level.
Level MeterThis meter represents the input signal level in dB, and is in fact the 
output of the Gates envelope follower. Since the envelope follower is 
driven by the greater of the left or right channel, this monophonic 
meter represents the greater of the two input signals.
Sustain LevelThis sets the gain level applied to the input signal when the ADSR 
engine is in the Sustain phase.
Release LevelThis sets the final gain level applied to the input signal when the Release 
phase is fully decayed. When set to the minimum (-70dB) the effective 
Release Level is -infinity, i.e., fully turned-off.
Hold TimeThis parameter allows additional time to be added onto the Sustain 
phase after the input signal falls below the Release Threshold before 
transitioning to the Release phase. This extension of the Sustain phase is 
useful for altering the tail dynamics of the sound.
Attack 
Lookahead/DelayThis parameter is adjustable in milliseconds to allow the Reshaper to 
either “look ahead” and advance (negative values) or “delay” (positive 
values) the response of the envelope detector relative to the dynamics of 
the input signal.
For example, negative lookahead values can cause the envelope 
detector to start the ADSRs Attack phase before the actual attack of the 
signal so as not to miss any audible transients. Likewise, positive delay 
values can be used to start the Attack “late”, so that signal transients are 
intentionally missed by the Attack. 
						

							5 - Effects
Core Effects Descriptions
E-MU Digital Audio System85
Release ThresholdThis parameter controls the level in dB below the Attack Threshold at 
which the Release phase of the ADSR will begin. 
Attack RetriggerBy default, when the value of this parameter is Disabled, the Reshapers 
ADSR engine will wait until at least the Release phase of a cycle before 
restarting a new Attack phase.
By setting Attack Retrigger to Enabled, however, the Reshaper becomes 
sensitive to new input signal transients during any phase of the ADSR 
cycle. In addition, enabling this parameter will also cause the attack to 
restart at the Release Level instead of whatever gain was being applied 
when the new attack arrived.
Attack CurveThis parameter allows the gain during the Attack phase to follow one of 
3 curves: linear, logarithmic, or exponential. Because the ADSR 
computes gain using linear coefficients, the exponential curve comes 
the closest to being a “constant in dB” gain ramp. A linear curve 
provides a somewhat more immediate turn-on, while the logarithmic 
curve presents a very abrupt turn-on. 
Release CurveThis parameter selects gain curves exactly as for the Attack Curve 
parameter, except that the selected curves apply to both the Decay and 
Release phases of the ADSR. Parameter Description 
						

							5 - Effects
Core Effects Descriptions
86Creative Professional
Multimode EQ
The Multimode EQ is a flexible stereo filter that is capable of implementing a range of 
powerful filter topologies. It is useful both for utility EQ applications and also for 
special effects.
The Multimode EQ is built from an array of filter sections that can be configured to 
support:
•Lowpass filters with up to 48dB/octave rolloff
•Highpass filters with up to 48dB/octave rolloff
•Highpass + Lowpass series or parallel combination with up to 
24dB/octave rolloff 
•Bandpass filters with up to 24dB/octave rolloff
•Bandcut filters with up to 24dB/octave rolloff
In addition to cutoff or center frequency parameters, each of the above filter types also 
has a switchable rolloff rate and adjustable resonance. 
A Filter Edit parameter  controls whether the Multimode EQ operates in Stereo, where 
filter parameters are adjusted identically for both channels, or split Left and Right, 
where the left and right channels support completely independent filter types and 
parameter values.
In addition to a standard Bypass switch, the effect offers an adjustable wet/dry mix 
parameter. While not normally found on EQ sections, adjustable wet/dry mixtures can 
be useful for generating phase cancellation and other special effects.
Applications
•Basic Tone Control - for fidelity enhancement
•Rumble Filter - use the highpass configuration with 48dB/octave rolloff below 
50Hz.
•Subwoofer Support - use the lowpass configuration with 48dB/octave rolloff 
below 100Hz.
•Lo-Fi Effect (telephone, walkie-talkie, guitar mini-amp, distance simulation)
•Extreme Spectral Shaping - use Highpass+Lowpass, Bandpass or Bandcut with 
independent hi/lo resonance
•Pseudo-stereo Effect - apply slightly different EQ to left and right channels to 
broaden the spread of a mono signal
•Cross-over - left and right channels split a mono signal between highpass and 
lowpass with a sharp transition region. 
						

							5 - Effects
Core Effects Descriptions
E-MU Digital Audio System87
Parameters
While the Multimode EQ has many parameters applicable to the various possible 
configurations of channels and filters, it selectively enables or hides parameters 
depending on their applicability to the current configuration. As a result, not all of the 
parameters listed below appear on-screen at the same time.
Lowpass
The frequency response of the lowpass filter looks something like the diagram below:
In this mode, the Lowpass filter can have up to a 48dB/octave rolloff slope. In this mode 
the Lowpass Rolloff, Lowpass Frequency and Lowpass Resonance parameters are 
available for editing the filter response.
Highpass
The frequency response of the highpass filter looks something like the diagram below:
In this mode, the Highpass filter can have up to a 48dB/octave rolloff slope. The 
Highpass Rolloff, Highpass Frequency and Highpass Resonance parameters are available 
for editing the filter response.
ParameterDescription
Filter EditThis parameter controls whether the filter editing parameters apply to 
both left and right channels in tandem (Stereo), only to the left channel 
(Left) or only to the right channel (Right).
Filter ModeThis parameter selects one of 5 different filter types: Lowpass, Highpass, 
Lowpass+Highpass, Band Pass or Band Cut. 
						

							5 - Effects
Core Effects Descriptions
88Creative Professional
Highpass -> Lowpass
In this mode, the Lowpass and Highpass filters are connected in series and both sets of 
Lowpass and Highpass parameters are exposed and independently editable to create the 
overall filter response. The maximum rolloff slope of each filter is limited to 24dB/
octave in this mode.
In Highpass -> Lowpass mode, the effect does not place any limitations on the 
Frequency parameters of one filter relative to the other. In normal use, the Highpass 
Freq parameter will be less than the Lowpass Freq parameter, creating a bandpass-type 
response:
However, if the Highpass Freq parameter is greater than the Lowpass Frequency 
parameter, the passband effectively disappears, since the part of the spectrum which is 
above the highpass and below the lowpass is non-existent. As a result, youll hear a 
rapidly attenuating bandpass response as the corner frequencies diverge.
Note that while the Highpass -> Lowpass combination appears the same as the Band 
Pass filter, this mode is different in several important respects:
•The rolloff points are independently adjustable as individual frequencies rather 
than specified as a combination of center frequency and bandwidth.
•The rolloff slope of each High and Low filter can be specified separately while the 
Bandpass and Band Cut filters use the same slope.
•The Resonance of each High and Low filter can be specified separately while the 
Bandpass filter uses the same Resonance at high and low corner frequencies.
Highpass || Lowpass
In this mode, the Lowpass and Highpass filters are connected either in parallel, and 
both sets of Lowpass and Highpass parameters are exposed and independently editable 
to create the overall filter response. The maximum rolloff slope of each filter is limited 
to 24dB/octave in this mode.
In Highpass || Lowpass mode, the effect does not place any limitations on the Freq 
parameters of one filter relative to the other. In normal use, the Highpass Freq 
parameter will be higher than the Lowpass Freq parameter, creating a bandcut-type 
response: 
						

							5 - Effects
Core Effects Descriptions
E-MU Digital Audio System89
However, when the Highpass Freq parameter is lower than the Lowpass Freq parameter, 
the combined filter response is basically flat, since the passbands of each filter combine 
to admit the entire spectrum. An exception occurs when there is resonance added to the 
filters - youll hear the resonant peaks as increased gain above the otherwise flat spectral 
response.
Note that while the Highpass || Lowpass combination appears the same as the Band Cut 
filter, this mode is different in several important respects:
•The rolloff points are independently adjustable as individual frequencies rather 
than specified as a combination of center frequency and bandwidth.
•The rolloff slope of each High and Low filter can be specified separately while 
each side of the Band Cut filter uses the same slope.
•The Resonance of each High and Low filter can be specified separately while the 
Band Cut filter uses the same Resonance at high and low corner frequencies.
Band Pass
In this mode, the Lowpass and Highpass filters are connected in series to form a 
bandpass filter, whose Center Freq and Bandwidth parameters are used to generate the 
rolloff frequencies for the underlying Lowpass and Highpass filters. In this mode the 
rolloff slope on the high and low sides of the passband is symmetrical and is limited to 
a maximum of 24dB/octave. The Resonance is also common to both filter sections .
Band Cut
In this mode, the Lowpass and Highpass filters are connected in parallel to form a band-
cut filter, whose Center Freq and Bandwidth parameters are used to generate the rolloff 
frequencies for the underlying Lowpass and Highpass filters. In this mode the rolloff 
slope on the high and low sides of the cut-band is symmetrical and is limited to a 
maximum of 24dB/octave.The Resonance is also common to both filter sections .
18dB/oct24dB/oct
6dB/oct
12dB/oct
Resonance = 0
18dB/oct24dB/oct
6dB/oct
12dB/oct
Resonance = 0 
						

							5 - Effects
Core Effects Descriptions
90Creative Professional
RFX Compressor
The RFX Compressor is a full-featured stereo compressor effect which features the standard 
parameters available on most compressors as well as a collection of additional advanced 
parameters that are useful for more sophisticated applications and special effects:
•Threshold, Ratio, Attack and Release w/gain metering
•Auto-makeup gain
•Adjustable soft knee
•Adjustable lookahead/delay
•Noise gate (downward expander)
•Compressor “tail” expansion
•Program-dependent release
•Negative compression ratios
Signal Flow
The block diagram of the RFX Compressor is shown below.
Note that the effect is split between a signal path and a sidechain path that contains the 
compressors level detectors and gain computation. The signal path of the RFX 
Compressor is very close to a “straight wire”, with only a delay line and one gain control 
element inserted in it. The sidechain contains the bulk of the compressor algorithm and 
is responsible for computing the gain control signal. Signal multiplexers at the front of 
the signal path and sidechain allow linked stereo compression or split signal path/
sidechain processing.
The RFX Compressor does not have the input gain control that is found on some 
compressors. These are typically used to align the input signal range to the compression 
threshold. Instead, weve allowed the RFX Compressors Threshold parameter to operate 
over an exceptionally large range of 0-60dB so that it can be “steered” to the appropriate 
range of the input signal. The output Gain parameter also operates - either manually or 
automatically - over the unusually large range of -60dB to +60dB in order to renor-
malize the compressors output for the next stage of the signal path.
In L
In ROut
L
R
Out
Compressor
Lookahead
0-100mS
Compressor
Delay
Attack
Auto ReleaseRelease
Soft
KneeMax.
Comp.Neg.
Comp.
Compressor
Delay
0-50mSLevel
DetectorGain
Control
Threshold Ratio Gain
Gate
(& Sidechain)
Input
Mode
Gain
Cells
SIGNAL PATH
SIDECHAIN