CAKEWALK CA-2A User manual

CA-2A T-Type Leveling Amplifier
User Guide
Benutzerhandbuch
Guide d'utilisation

2
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LA-2A is a registered trademark of Universal Audio, Inc. Cakewalk’s products, specifically, the
CA-2A T-Type Leveling Amplifier, is developed by Cakewalk, Inc. based on its own modeling
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Visit Cakewalk on the World Wide Web at www.cakewalk.com..

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Table of contents
CA-2A T-Type Leveling Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Using CA-2A T-Type Leveling Amplifier. . . . . . . . . . . . . . . 15
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
LICENSE AGREEMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

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CA-2A T-Type Leveling Amplifier
Figure 1. CA-2A T-Type Leveling Amplifier.
VST and Audio Units (AU) version
SONAR ProChannel version

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CA-2A T-Type Leveling Amplifier is meticulously modeled after a legendary vintage electro-
optical tube compressor. This compressor, known for its automatic gain control characteristics,
delivers vintage sound with incredibly warm and rich compression. It is revered by audio
engineers worldwide for its trademark sound, and has been used on countless hit records since
the late 1960s. It is one of the true classics in the audio recording industry.
The purpose of a compressor is to limit the dynamic range of music or sound. Compression will
make the loud parts of the signal quieter, resulting in a more or less even level. Compression is
usually applied to compensate for the small variations in level that occur when a musician plays
an instrument or a vocalist sings a song.
CA-2A T-Type Leveling Amplifier is a soft-knee compressor that features program dependent
release times and a flat frequency response of 30Hz to 15kHz (see R37 control for frequency
response adjustment). The attack time is fixed at 10 milliseconds. The release time is roughly
60 milliseconds for 50% release, and 0.5 to 5 seconds for full release, depending on the
previous program material. The two-stage release results in very transparent compression
characteristics.
CA-2A T-Type Leveling Amplifier models the tubes and the T4 electro-optical device in the
original hardware units. The T4 circuit uses an electroluminescent panel to determine the attack
time, and an optical photo cell to determine the release time. All based on the incoming program
material. The T4 has very little distortion. To realize the characteristic sound of the original
hardware, the tubes are also modeled to add analog characteristics. Total Harmonic Distortion
(THD) comes from the four tubes in the original hardware, which slightly changes the signal
shape adding even and odd harmonics based on the frequency of the program material. The
THD has a slight effect on the output gain, less than 0.35% to 0.75% at +10 dB to +16 dB of the
program material.
The modeling of the tubes and the T4 circuit is what gives CA-2A T-Type Leveling Amplifier its
unique compression characteristics. The curves are “wobbly” and only reduce gain to a certain
point before “giving in” and letting the output level increase again. Unlike typical dynamics
processors that have a fixed compression ratio across all frequencies, the CA-2A T-Type
Leveling Amplifier gain reduction is different at different frequencies.
CA-2A T-Type Leveling Amplifier is suitable for just about any audio material. It sounds
especially good on vocals, and also works great on guitar, electric and upright bass, guitars,
piano, wind instruments, and other tracks that need gentle compression. It even works well on
full-program mixes.
This documentation describes the CA-2A T-Type Leveling Amplifier controls and parameters.
Note: The original hardware unit is mono, and can be linked with a second unit for stereo
leveling. CA-2A T-Type Leveling Amplifier operates in both mono and stereo modes
without a loss in stereo imaging.

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Highlights
• CA-2A T-Type Leveling Amplifier is available in the following formats:
•Mac OS X: Audio Units (AU) / VST3 (32-bit and 64-bit)
•Windows: SONAR ProChannel module / VST (32-bit and 64-bit)
• With only a few simple controls, CA-2A T-Type Leveling Amplifier is easy to use and
provides instant gratification.
• Warm, smooth and natural sounding compression characteristics.
• Frequency-dependent gain reduction.
• Compressor and Limiter modes.
• Up to 40 dB of gain reduction.
• Sidechain input.
• Parameters can be automated.
What can you do with CA-2A T-Type Leveling Amplifier?
The purpose of CA-2A T-Type Leveling Amplifier is to limit the dynamic range of a signal by
reducing the amplitude of its transient peaks. CA-2A T-Type Leveling Amplifier varies its gain in
response to the level of the input signal. Large input signals result in less gain, thus reducing or
“compressing” the dynamic range of the signal.
In a typical mix of audio material, there are a few peaks that are much louder than the average
signal. Increasing the overall volume would make these peaks exceed the maximum output
level, causing unpleasant distortion in the music.
Compression reduces the level of any peaks above the threshold so the average level can be
boosted.
Peaks

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Limiting versus compression
A compressor typically has a compression ratio lower than 10:1. A limiter has a compression
ratio higher than 10:1. For example, with a ratio of 4:1, an input level increase of 4 dB will only
result in a 1 dB output level increase.
The threshold is the level the input signal must reach before compression begins. Gain
reduction is only applied to audio that exceeds the threshold.
When an audio signal is below this threshold the compressor acts like an amplifier and there is
no gain reduction. Above the threshold, the slope becomes less than 45 degrees, indicating
gain reduction and hence compression. The point at which a compressor transitions into
compression is commonly called the knee.
Figure 2. Compression/limiting curves.
Compression is suitable for leveling and reducing the general dynamic range of individual
instrument tracks such as vocals and drums.
Limiting is used to limit the dynamic range and increasing the perceived overall level of the mix,
and to prevent the audio signal from exceeding a specific level.
Note: The CA-2A T-Type Leveling Amplifier compression ratio is frequency-dependent. In
Limit mode, the compression ratio can go as low as 4:1 for low frequencies.
Limit curve (4:1 to 20:1)
Compress curve (3.5:1 to 6:1)
Threshold
Input level
Output
level
No gain reduction
Gain reduction amount
Knee

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Controls
There are two versions of the CA-2A T-Type Leveling Amplifier interface: one version for VST
and Audio Units plug-ins, and one version for the SONAR ProChannel module.
Figure 3. VST and Audio Units (AU) controls.
A. VU meter B. VU meter mode C. Options menu D. Limit/Compress E. R37 F. Gain G. Peak
Reduction H. Enable/disable
Figure 4. SONAR ProChannel module controls.
A. Clipping LED B. CA-2A T-Type Leveling Amplifier enable/disable C. VU meter D. Limit/Compress
E. VU meter mode F. Gain G. Options menu H. R37 I. Peak Reduction
A B
D F G HE
C
B
H
D
A
I
F
C
E
G

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CA-2A T-Type Leveling Amplifier contains the following controls:
•Clipping LED (ProChannel only). Shows if the input signal to the CA-2A T-Type Leveling
Amplifier module is clipping. If there is any distortion in the ProChannel signal chain, the
clipping LEDs let you identify where the clipping occurs.
•Enable/disable. Enables/disables the CA-2A T-Type Leveling Amplifier.
•Limit/Compress. Changes the dynamic processing ratio between compressor and limiter.
The compression ratio fluctuates depending on the frequency of the incoming signal.
•Limit. In Limit mode, the compression ratio ranges between 4:1 for low frequencies and
20:1 for high frequencies. Limiting can be used in many ways, including:
• Creating a louder or fuller sound by limiting the dynamic range and increasing the
perceived overall level of the mix.
• Increasing the volume and density of individual instruments in the mix.
• Preventing digital overs and other types of overload protection. Think of it as an audio
safety net that puts a cap on the overall level. A limiter is the most transparent way to
boost average level without clipping.
• Creatively sculpting a sound’s dynamics.
•Compress. In Compress mode, the compression ratio ranges between 3.5:1 for low
frequencies and 6:1 for high frequencies. This method is suitable for leveling and
reducing the general dynamic range of individual instrument tracks such as vocals and
drums. It produces a more gentle compression.
•VU meter. The VU meter can be switched to show gain reduction or output level, depending
on the position of the VU meter mode knob.
•VU meter mode. Switches the VU meter to show gain reduction or output level.There are
four available modes:
•GR. Displays the instantaneous gain reduction in dB. During periods of no gain
reduction, the pointer will return to 0 VU on the meter scale.
•+10. Displays the post-processing output level, referenced to +10 dBm (analog
emulation).

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•+4. Displays the post-processing output level, referenced to +4 dBm (analog
emulation).
•dBFS. Displays the post-processing output level in the digital domain. This is the true
output meter for digital audio, and is the recommended setting when monitoring output
level.
•Gain. Adjusts the post-compression output level, or make-up gain. Use this control to make
up for the gain lost by the peak reduction. The Gain knob has no affect on the amount of
compression. To adjust the knob in fine increments, hold down the SHIFT key while moving
the knob.
•Peak reduction. Adjusts both the threshold and the amount of compression (gain
reduction). If the input signal level is below the threshold, no compression takes place. Turn
the knob clockwise for more compression, or counter-clockwise for less. To adjust the knob
in fine increments, hold down the SHIFT key while moving the knob.
•R37 (High Frequency Pre-emphasis trim). This control adjusts the gain reduction
frequency response. The original hardware unit was designed for leveling in radio and TV
broadcast applications. Due to an increase in high frequency content in FM broadcasting,
the R37 control adds gain reduction at frequencies above 1kHz, based on the program
material. Use this control to reduce or prevent over-modulation caused by the pre-emphasis
(high-frequency sensitivity). When set to the FLAT position, gain reduction is applied equally
on all frequencies. When the control is moved toward the HF position, gain reduction is
increased on the high frequencies. Experiment to achieve a good balance between low and
high frequency limiting. This control is often useful for de-essing vocals (cut down sibilance
by compressing high frequencies), but the FLAT setting is recommended for most music
applications. To adjust the knob in fine increments, hold down the SHIFT key while moving
the knob.
Note: The output meter of the CA-2A Leveling Amplifier has a different value than the
original hardware it emulates. With analog hardware, 0 dB typically represents the nominal
signal level. Anything above 0 dB is considered “headroom” in the analog domain. Its
clipping or peak level is often around +20 dB, depending on the manufacturer. In this case,
the hardware being emulated has a nominal level of +10 dB and peaks at +16 dB. The
original hardware is analog, therefore the output metering does not conform to the dB-FS
(Decibel-Full Scale) range of a DAW (Digital Audio Workstation) such as SONAR. In order
to keep metering accurate in the digital domain, CA-2A Leveling Amplifier also includes a
dBFS meter option, which accurately depicts the level meter and headroom in the digital
domain.

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•Options menu. The Options menu contains the following options:
•Photocell Memory. The CA-2A T-Type Leveling Amplifier emulates a classic hardware
optical compressor. An optical compressor is different from an FET style compressor, in
that it uses a luminescent panel and photocell to determine the amount of compression,
attack and release times. These controls are not fixed, and are dependent on the
reaction of the photocell, determined by the audio source. The photocell has unique
properties that make optical compressors the prime choice for vocals and other material
with smoother transients. But the hardware is not necessarily perfect. Longer, multi-stage
release times result from high levels of gain-reduction. This will cause the photocell to
“remember” its “on” or “lit” state, for a longer period of time. Attack-times become
snappier as the input becomes more active, and relaxed (slower) during periods of less
activity. After long periods of silence, the compressor can become very sluggish in its
ability to reduce the gain of sudden transients. Under these conditions, the onset of a
new transient can result in a “pop” at the output as the compressor is “waking up”. Since
this behavior might not be desirable, we have included the Fast Reset mode to allow a
faster wake-up time, and to avoid the “pop”. The Classic mode sticks to the true
emulation and responds like the original hardware. To change the mode, click the
Options menu button , point to Photocell memory and choose Classic or Fast
Reset on the pop-up menu.
•External Side-chaining. CA-2A T-Type Leveling Amplifier lets you use a secondary
audio input to control the Gain Reduction control. Sidechaining is typically used with
compressors to limit one signal depending on the signal level of another. Common
applications are to reduce the level of a bass guitar when there is a kick drum, or to
reduce the level of music whenever a speaker talks (often used for background music in
radio- and television programs). Another use for the CA-2A Sidechain inputs is frequency
dependent compression. To enable/disable sidechaining in CA-2A T-Type Leveling
Amplifier, click the Options menu button , point to External Side-chaining and
choose Enabled or Disabled on the pop-up menu. Please consult your host program’s
documentation for information about using sidechain inputs.
•Open Documentation. Opens the CA-2A T-Type Leveling Amplifier User Guide.

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Using CA-2A T-Type Leveling Amplifier
CA-2A T-Type Leveling Amplifier is suitable for just about any audio material. It sounds
especially good on vocals, and also works great on guitar, electric and upright bass, guitars,
piano, wind instruments, and other tracks that need gentle compression. It even works well on
full-program mixes.
Percussive instruments that have a lot of peaks, such as drums, may require more care.
Although CA-2A T-Type Leveling Amplifier works great for certain kick drum sounds, you may
want to combine CA-2A T-Type Leveling Amplifier with another compressor with a faster
release time and more precise control. For details, see “Using CA-2A T-Type Leveling Amplifier
on drums” on page 16.
Unlike a traditional compressor that has Ratio, Threshold, Attack, Release and Make-up Gain
controls, CA-2A T-Type Leveling Amplifier is very straightforward with only two primary controls:
Gain and Peak Reduction. Peak Reduction controls the amount of compression and Gain
controls the post-processed output level.
The most common problem caused by the use of a compressor/limiter is excessive distortion.
This normally indicates that the limiter is active too much of the time (threshold is too low). To
correct the distortion, turn the Peak Reduction knob counter-clockwise.
Typical workflow
1. Insert CA-2A T-Type Leveling Amplifier on a track or bus, normally before effects like
reverb and delay.
2. While listening to the project, adjust the Peak Reduction control until the compressor
exhibits the desired amount of compression. You may want to set the VU meter to show
gain reduction (GR). A good target is to keep the gain reduction around 4-8 dB
continuously.
3. If desired, adjust the R37 (pre-emphasis) control according to the amount of high frequency
content in the audio material. Turn the knob counter-clockwise to increase compression of
high-frequency content, such as vocal sibilance.
4. Adjust the Gain control to achieve the desired output level. You may want to set the VU
meter to show output level (dBFS, +10 or +4).
5. If your host program has an effect bypass toggle, use the toggle to compare the
compressed signal with the unprocessed signal.

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Sidechaining
CA-2A T-Type Leveling Amplifier lets you use a secondary audio input to control the Gain
Reduction control. Sidechaining is typically used with compressors to limit one signal
depending on the signal level of another. Common applications are to reduce the level of a bass
guitar when there is a kick drum, or to reduce the level of music whenever a speaker talks (often
used for background music in radio and television programs). Another use for the CA-2A
Sidechain inputs is frequency dependent compression.
To enable/disable sidechaining in CA-2A T-Type Leveling Amplifier, click the Options menu
button , point to External Side-chaining and choose Enabled or Disabled on the pop-up
menu.
Please consult your host program’s documentation for information about using sidechain inputs.
Using CA-2A T-Type Leveling Amplifier on drums
Used carefully, CA-2A T-Type Leveling Amplifier can make drum tracks sound fuller and bigger.
By itself, however, CA-2A T-Type Leveling Amplifier is not well-suited for compressing drums
and other percussive instruments that have lots of peaks. The reason is due to the slower
release time and lack of precise control, thus changes in the input level cannot be compensated
for quickly enough to make the output volume totally consistent.
A good compression trick is to chain different compressors together on the same track. This lets
you use another compressor with a faster release time and more precise control as a peak
limiter to first tame the peaks before they reach CA-2A T-Type Leveling Amplifier, then use
CA-2A T-Type Leveling Amplifier for general compression.
As a starting point, place a separate peak limiter type compressor in front of CA-2A T-Type
Leveling Amplifier. Configure the peak limiter compressor with a high compression ratio, like
12:1, and a fairly fast attack and release. Set the input gain carefully so the highest peaks are
reduced by 2-3 dB, then adjust the output gain until you can’t hear a difference between the pre-
and post-processed level (frequently enable/disable the peak limiter compressor so you can
compare the pre- and post-processed levels). The goal is to only flatten the highest peaks, and
not compress the overall audio signal.
Next, configure CA-2A T-Type Leveling Amplifier for general compression: set Compress/Limit
to Compress, and adjust Gain and Peak Reduction to taste.
Note: When chaining multiple compressors together, each successive compressor should
have a lower compression ratio than the one before it.

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In summary, first use a compressor with precise control to act on the peaks, followed by CA-2A
T-Type Leveling Amplifier for general compression.
Tip: Another common technique is to use parallel bus compression. This is achieved by
sending all of your drum tracks to a bus, replicating your level and pan controls for each
auxiliary send. Insert CA-2A Leveling Amplifier on the bus, and use a fairly large amount of
peak reduction. Finally, blend the bus from 0 dB upward, with the drums soloed, until the
desired amount of parallel compression is achieved.

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Symbols
+10 12
+4 13
A
Audio Units (AU) 9
C
Classic 14
Clipping LED 12
Compression 10
Controls 11
D
dBFS 13
Documentation 14
E
Enable/disable 12
F
Fast Reset 14
G
Gain 13
GR 12
H
Help 14
High-frequency sensitivity 13
L
Limit/Compress 12
Limiting 10
M
Meter 12
Meter mode 12
O
Options 14
Options menu 14
P
Peak reduction 13
Photocell memory 14
Power 12
Pre-emphasis trim 13
ProChannel 9
Index

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R
R37 13
S
Sidechain 16
Side-chaining 14
Sidechaining
enable. 14
V
VST 9
VST3 9
VU meter 12
VU meter mode 12
W
Workflow 15