Aphex Dominator II User manual

DOMINATOR II
PRECISION MUL TIBAND
PEAK LIMITER
OPERATING GUIDE
APHEX SYSTEMS, LTD.
11068 Randall Street, Sun Valley, CA 91352 [phone]

WARNING
TO REDUCE THE RISKS OF FIRE OR ~LECTRIC
SHOCK, DO NOT EXPOSE THIS APPLIANCE TO
RAIN OR MOISTURE

Dominator II
Errata And Modifications To The Operating Guide
Due to circuit changes, several parts of the manual are now
irrelevant or inaccurate. Please Note the followi~q changes.
~. section 3.0, Basic Setup, paragraph (5.) should read thusly:
5) Feed speech or music program at normal level; adjust ZNPUT
control to generate at least 6 to adB of limiting. Do not use
a steady tone for this purpose but a 1KHz tone burst with
30msec on and 300msec off may be used.
2. section 5.8.2, ALT Generator:
The circuit revision defeats the tone detector function and
places a direct connection from collector to emitter of Q3.
Therefore, any discussion of the tone detect circuit is
irrevelant. All discussion including Q3 should be taken to
assume Q3 is always conducting. The Dominator II no longer
recognizes test tones.
3. The parts list should be updated to reflect several new
values. .
Main Audio PCB:
R317(L,M,H)
was
10KO
is now 4K99
R417(L,M,H)
was 10KO is now 4K99
D301(L,M,H)
was
1N914B diode
is now
D401(L,M,H)
was 1N914B diode
is now
Aux
Control PCB:
C6 was O.OOlUF is now O.OlUF
R32 was 4K99 is now lOOK
5.6meg
resistor
5.6meg resistor

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DOMINATOR II
PRECISION MULTIBAND PEAK LIMITER
1.0 INTRODUCTION
After its introduction in 1985, the Studio Dominator became the
world standard for peak limitin.g because of its transparency and
effectiveness. However, un willing to rest on its already established
reputation, Aphex Systems. Ltd, has continued to develop new
techniques. The result is the Dominator II.
As a direct descendant of the original, the Dominator II has the
same primary functions and applications. Its many performance
improvements lie in the areas of dynamic range, distortion,
flexibility I and ease of setup.
Although those familiar with the Studio Dominator already know
much of the information in thls manual, Aphex recommends that
these people as well as those new to Aphex Dominators read this
manual.
The Dominator II is a stereo multiband peak limiter with absolute
zero overshoot. Once the PEAl{ CEILING is set. there is no
higher amplitude in the output. Awareness of headroom limitations
and the price of exceeding those limitations I important for any
audio application, is critical for most. especially digital. The
Dominator II allows users to work confidently I creatively. and
quickly by freeing them from the fear of "crashing".

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Achieving this brick wall result while retaining complete fidelity
is the art and science of the Dominator II. Because of its
exceptional function and performance, it has applications in a great
many audio fields, including:
. BROADCASTING-PRODUCTION, AND TRANSMISSION FOR AM.
FM.
AND TV
_RECORDING
_SAMPLING
.MIXING
_ MASTERlNG-CD. FILM, AND ANALOG DISK
_ SOUND REINFORCEMENT
. SATELLITE AND STL UPLINK
.LOCATION RECORDING
_VIDEO POST-PRODUCTION
. TAPE DUPLICATION
_TELECONFERENCING
1.1 DYNAMIC RANGE CONTROL
Essential to a full understanding of the operation and application of
the Dominator II is a knowledge of the definitions and applications
for each type of gain control: leveling, compression. limiting, and
clipping.
1.1.1 Leveling
Leveling has high compression ratios with slow attack and release
times. Because of its very slow time canstan ts, leveling has no
effect on short term changes in average levels or on transient peaks.
Therefore, it is used to maintain a constant output level without
affecting the short term dynamics by adjusting for long term changes
in the input signal. Typically. the threshold is set low so that low
level signals will be brought up.

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1.1. 2 Compression
Compression has low ratios with faster attack and release times. A
compressor forces a wide dynamic range into a smaller range. The
size of the resultin g dynamic range depends on the level of
the threshold, the height of the ratio used, and the speed of the
attack and release. The higher the ratio and the faster the time
constants, the greater the effect on the short term dynamics (the
actual quality and fidelity of the sound); these effects are often
used creatively. Normally, since one of the desired results of
compression is to bring up low level signals, the threshold is set
low.
1.1. 3 Limiting
Limiting has high compression ratios (usually defined as greater than
8:1), fast attack and, depending on the particular application and
desired sound, slow or fast release times. Since it is normally used
to keep high levels down, the threshold is set high. Inasmuch as
the ratios are high, as the input is driven further into limiting, the
dynamic range of the output becomes 'tighter', an effect that may
or may not be desirable. If the attack times are set to control only
the average level, and allow for peaks above the threshold to pass I
the limiter is considered a program limiter. When the speed of the
attack times is increased to control peaks, the limiter is considered
a peak limiter.
1.1.4 Clipping
Regardless of a limiter's attack time I there is a finite amount of
time before the detector circuits cause the gain circuits to reduce

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the output below threshold. Also, extremely fast gain modulation
introduces unwanted audible effects. Therefore, clipping with its
infinite ratios and instantaneous attack and release, functions as an
absolute brick wall. To control the pBaks, clipping literally shaves
off the peaks of the wave above threshold without changing the
amplitude of the remainder of the wave. Done properly, clipping
is inaudible and. under certain circumstances, actually enhances the
audio. Done improperly, however, clippin g produces very audible.
obnoxious effects.

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2.0 FUNCTIONAL DESCRIPTION
Traditionally, peak limiters have been designed with fast attack
times: the faster the attack time, the lower the amount of overshoot
above threshold. The drawback to these fast attack times I however,
is that the limiter is triggered off each transient, even extremely
short ones. The sonic result is hole punching and · overall lower
density (peak to average ratio). On the other hand, while slower
attack times result in better sonic performance, the overshoots
cause distortion, or the overall level must be reduced to accommodate
the overshoots. The Dominator II overcomes both drawbacks by
combining limiters with fairly slow attack times and clipping, in an
interacti ve, self-adjusting manner.
The Dominator II has been designed as a unity gain device with an
adjustable threshold. Since there is zero overshoot over threshold,
users have only to set the PEAK CEILING to the level at which
peaks must stop (fDr example: 100% modulation). In other words,
set it and forget it!
2.1 MULTIBAND VERSUS WIDEBAND PROCESSING
A significant problem with wideband processing is "spectral gain
iotermodulation" which occurs when one part of the spectrum
controls the level of another part. A typical situation is a vocalist
being 'sucked down' whenever the kick drum hits.