Bitcom User’s Guide
Audio Damage, Inc.
Release 1.0
The information in this document is subject to change without notice and does not represent a commitment on
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© 2013 Audio Damage, Inc. All rights reserved.
Credits
Software Design and Construction, Documentation
Chris Randall
Adam Schabtach
Field Testing
Jens Ågren
Stephen Boyd
Don Gunn
Steve Hamann
Jeff Laity
Made Possible By
Elle
Tracie
Fuzzy Logic
Alfred
Chica
Edwin
Garrus
Madeline
Pablo
Tali
Zed
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Introduction
Bitcom was created in part because of an argument. The argument essentially went like this: Chris asked
Adam whether a particular bit-oriented operation could be applied to digital signals. Adam said yes, but that
doing so didn’t particularly make much sense from a digital signal-processing perspective. Chris asked
whether it could be done anyway. Adam said yes, but tried to explain why it didn’t make any sense and why
the end result wouldn’t be useful. Chris suggested that Adam’s notion of what is and isn’t useful to Audio
Damage customers, creative types that they are, might be limited by Adam’s engineering-centric worldview.
Adam suggested that Chris should go learn something about binary numbers so that an intelligent
conversation about his suggestion could be had, and hence the suggestion could be unanimously dismissed in
favor of more promising ideas. Chris asked whether Adam could knock together a prototype for him anyway,
just so we could listen to it. Adam became grumpy but decided that the only way to get Chris to let go of the
idea was to build the prototype. Chris went off to sit in park and watch rainbows while Adam built the
prototype.
Chris won the argument. Bitcom was the result.
System Requirements
To use Bitcom, you'll need a Steinberg VST-compatible host application which conforms to the VST 2.4
specification, and a computer capable of running it. For the Audio Unit version of Bitcom, you’ll need an
application capable of hosting Audio Unit plug-ins, and an Apple computer with an Intel CPU capable of
running it. Bitcom requires a host that supplies timing and transport information to plug-ins, and will not work
with hosts such as Sound Forge that do not provide this information.
We support the use of Bitcom under Microsoft Windows XP, Vista, or Windows 7 or 8; and Apple OS X version
10.6 or newer.
Installation
Double-click the Bitcom Installer icon, and follow the instructions. During the installation process the installer
will ask you to enter your registration code. Your registration code uniquely identifies your purchase, and you
will need it if you need to reinstall your plug-in (for example, after upgrading to a new computer). You can
retrieve your registration code from your account on the Audio Damage website if necessary. Please don’t
share it with your friends. We’re delighted if you like our products so much that you want to share them, but
please ask your friends to buy their own copy so that we can keep making new products.
On OS X, the installer installs the Audio Unit and VST versions of Bitcom by default. If you click the Customize
button you can choose to not install one or more of these formats. There‘s no need to install formats that you
don‘t use, but on the other hand they don‘t take up much space if you do install them. The OS X versions are
combined 32/64-bit binaries.
If you‘re running a 64-bit version of Windows, you can choose to install either 32- or 64-bit versions of
Bitcom, or both. (There is no reason to install 64-bit plug-ins on a 32-bit version of Windows, and there are
good reasons to not do so.)
How It Works
In a nutshell, Bitcom is an unusual type of digital distortion generator, driven by a step sequencer. Each step
in the sequence has eight bit buttons. The state of the bit buttons, each either on or off, changes how Bitcom
distorts the signal. In addition, there are three flag buttons for each step. The flag buttons turn Bitcom’s
internal synthesizer on and off, allow the input signal to pass through without being distorted, and cause the
bits for the step to be set randomly. Bitcom thus produces rhythmic changes in timbre by distorting the signal
differently (and optionally adding a signal of its own) as it moves from one step to the next, in sync with your
host DAW’s transport. It’s worth mentioning that by “distort” we don’t mean just some lame soft clipping or
even the usual bitcrushing—we mean Bitcom can totally destroy your signal, leaving only a vague
approximation of the original buried in glorious digital noise.
Explaining exactly what Bitcom does requires speaking in
terms of binary math and computer operations, and that
explanation doesn’t convey how Bitcom actually sounds.
Instead, we’ll look at a series of images of Bitcom’s output
and explain what’s happening. We’ll use a sine wave as our
input signal. The simplest of all periodic signals, one cycle
of the humble sine wave looks like the image on the right—
no sharp edges, no jumps, just a smooth, continuous
undulation. It sounds pretty boring by itself, but add
together enough of them and you can produce any other
periodic sound. We’re using it here because it serves nicely
to illustrate Bitcom’s effect.
Bitcom’s bits buttons and flag buttons are shown in the image
on the right.
The numbers across the top enumerate the steps. Each step’s
buttons are arranged in a column, with the bits buttons on top
(as suggested by the cunning placement of the word “BITS”
on the right) and flag buttons below. We’re going to work with
just one set of bits buttons, the first one on the left. You’ll see
it peeking out on the left in the following screen shots.
If we turn on all of the bits, the output signal is passed with nearly no distortion. It looks so much like the
input signal that you won’t see any difference, given the resolution of the image1:
1
The oscilloscope screenshots were created with the Tone Generator and Scope plug-ins that are part of Studio One, a
product of PreSonus Audio Electronics, Inc.
Each of the eight bits allows part of the input signal to pass through to the output. These parts are added
together to form one output signal. In rough terms, the upper bits correspond to the bigger parts of the input
signal, and the lower bits correspond to the smaller parts. Putting it another way, the upper bits select the
parts of the signal that correspond to big changes in loudness, while the lower bits select the fine details. In
isolation, any one of these parts doesn’t tell you much about the signal, but added together they make up the
whole. If we turn on just the uppermost bit, we get a very chunky approximation of the signal:
That top bit selects just the part of the input signal that corresponds to the loudest part of the signal. If we
didn’t know what the input looked like, we’d have a hard time guessing by looking at this output. Most of the
original just isn’t there. If we listened to it, we’d hear a loud, buzzy signal with a lot of aliasing. Add the next
bit down and we get a slightly closer approximation of the original, shown on the next page:
If we add the next bit down we get closer to
reproducing the input. If you squint your
eyes, or take off your glasses if you wear
any, you’ll see that the output is now not
too far from the shape of the sine wave
input. You can guess what would happen if
we were to continue turning on the bits
buttons from top to bottom: the output
would become closer and closer to the
original sine wave. That’s how a standard
“bit crusher” or bit-depth reducer works: it
throws away the bits that represent the
small details in the signal, leaving you with
a noisier approximation of the input signal.
Now at least we could say that the input
signal is something other than a square
wave, because of those intermediate steps
in the output. Still, most of the detail of
the input is gone—no smooth changes
anywhere.
These effects always operate as we’ve
proceeded here: they turn the bits on or
off, but only working from one end or the
other, and only by turning off the smaller
bits. Bitcom, on the other hand, lets you
turn on or off any bit. For instance, if we
turn on just the third bit from the top, we
get the output shown on the top right of
this page.
Remember when we said that any one part
of the signal, in isolation, doesn’t tell you
much about the signal? Now you see what
we meant.
Here’s an analogy: Imagine looking at just
a single row of pixels on your computer
screen. You’d have no idea what was
actually being displayed. If you looked at a
few other rows you still wouldn’t know
whether your screen was displaying a
picture of Ke$ha or goatse. It’s not until
you can see most of the rows that the
original image is discernible. Bitcom
operates the same way: if most of the bits
are turned off, the output bears no
resemblance to the input, but is gloriously
distorted. If some of the bits are turned on,
you get strange conglomerations of parts of
the original, like the output shown on the
lower right.
Earlier we said that the lower bits correspond to the smaller details, so you might be wondering what happens
if you turn on just the bottom button. If you think that you’d hear just a teeny little signal, you’d be right,
except that Bitcom has another trick up its sleeve. Here’s what you get:
Not at all teeny, eh? What’s happening is that since the detail parts of the signal are necessarily much quieter
than the original, Bitcom looks at the bits that you’ve turned on and attempts to adjust the level of the output
signal to compensate. There’s nothing intelligent or graceful about how it does this, and the end result is
destruction of the signal’s dynamic range as well as its tone.
So, that’s what Bitcom does: different settings of the bits buttons produce different approximations of the
input signal. How the result sounds is not always readily predictable; Bitcom’s effect varies wildly with the
loudness, frequency, and pitch of the input signal. Combine this with a 16-stage sequencer, an internal tone
generator, and automatic and manual randomization, and Bitcom becomes a strange and wondrous source of
noise. Have an appropriate amount of fun.
Operation
Bitcom can be used in either a mono or stereo context. When used as a stereo plug-in, the input channels are
processed separately. Bitcom is probably most useful as an insert effect, but there’s no reason you can’t use it
in a send/return loop. If you do so, you’ll probably want to set its MIX knob to 100%.
The controls in Bitcom’s window are grouped into areas by their function. We’ll look at each area in turn.
Button Matrix
If you read at least partway into the “How It Works” section above, you already know what the Button Matrix
looks like. The buttons are arranged in a matrix, with each column of the matrix containing the buttons for
one step. The BITS buttons turn different parts of the signal on and off.
Click the individual buttons to turn the
individual bits on and off. You can also
drag across the buttons to change many
at once.
The three rows of buttons at the bottom
are called the Step Flag buttons, or just
the flags. They modify what happens
when Bitcom’s sequencer reaches the
corresponding step:
RAND: if a step’s RAND flag is
turned on, the step’s Bits are
randomly turned on or off each
time the sequencer reaches this
step.
SYNTH: if the SYNTH flag is on, Bitcom’s internal synthesizer is turned on for the step. We’ll have
more to say about this synthesizer later, but remember that this flag has to be turned on if you want
to hear the synthesizer at all.
DRY: turn on the DRY flag and Bitcom is essentially turned off for this step. The input signal passes
through Bitcom without alteration.
The little dot above the flag buttons indicates which step is currently active. This dot skips along from left to
right as the music plays.
Sequencer Controls
On the right of the button matrix you’ll find the controls for Bitcom’s sequencer. The STATUS buttons are
possibly the most important: click on the RUN button to make the sequencer run, and click on the IDLE button
to stop it. Bitcom’s sequencer is locked to your host program’s transport, and hence will run and stop when
your host runs and stops.
The STEPSIZE buttons set how rapidly Bitcom’s sequencer moves
from one step to the next by choosing the metrical unit for one
step. If the 1/16 button is set, for instance, Bitcom’s sequencer will
advance with each 16th note. The SWING knob varies Bitcom’s
rhythmic feel to line up its sequencer with source material with a
swing or shuffle feel. If the SWING knob is at 50%, the sequencer
has straight timing and all steps will have the same duration. As
you turn up the SWING knob, the even-numbered steps get longer
and the odd-numbered steps get shorter.
Finally, the RESET knob sets the step at which the sequencer jumps back to step #1. If you set the RESET
knob to 16, Bitcom will cycle through all 16 steps. If you set it to 1, Bitcom will stick stubbornly to the first
step.
To maintain some semblance of sanity, Bitcom also resets its sequencer to step #1 when it perceives that
your host sequencer has reset its own transport position, for instance when you jump the playback position
back to the beginning of your song.
Synth Controls
Bitcom has a simple internal synthesizer; its controls are found below the button matrix. Starting at the left
we have two buttons, labeled WAVEFORM, which select one of two wave shapes, PULSE and TRI. The PULSE
choice gives you a rectangular wave shape whose pulse width (or duty cycle, as it’s known in engineering
circles) can be varied with the SHAPE knob. The TRI setting produces a triangular wave that can be skewed to
produce a ramp wave. With the SHAPE knob at 50% you get a symmetric triangle wave; with the knob at
95% (its maximum setting) you get a ramp wave that rises at a fixed rate and drops back to zero almost
instantly.
With either setting of the WAVEFORM
switch, moving the SHAPE knob can
produce some nice timbral changes—nice
enough that we hardwired the SHAPE knob
to MIDI controller #1, the modulation wheel
on most keyboards. If you route MIDI data
to Bitcom in your host software, you can use
a mod wheel to change the shape of the
wave.
The TUNE knob sets the frequency of the synthesizer. In the absence of incoming MIDI data, this is the only
control you have over the synth’s musical pitch. It’s marked in MIDI note names and numbers, and covers the
full 127-note range from sub-audio to annoy-your-dog-audio. Bitcom’s extreme approach to bit destruction
produces all sorts of aliasing so sweeping the TUNE control near either extreme of its range, perhaps with the
automation feature of your host program, can produce all sorts of rather horrible noises interesting and
unusual tones.
The FINE knob adjusts Bitcom’s pitch by as much as a half-step sharp or flat. It’s marked in cents, or 1/100
ths
of a semitone. If the input signal is slightly out of tune you can use the FINE knob to tune Bitcom’s pitch to
match. Or, more likely, you can use the FINE knob to detune Bitcom’s pitch relative to the input signal, thus
creating some beat frequencies from the two signals and hence a more complex sound for Bitcom to beat on.
The LEVEL knob sets the loudness of the synthesizer. It has a range of -60dB, which will effectively silence it,
to 0dB, a full-amplitude digital signal.
The OUTPUT switches choose one of three operational modes for the synthesizer:
ON: Bitcom’s synthesizer is always on, with its loudness entirely determined by the LEVEL knob.
ENV: The synthesizer’s loudness is controlled by an envelope follower fed by the plug-in’s input signal.
As the input signal gets louder, so does the synthesizer. If the input signal is silent, the synthesizer is
silenced.
MIDI: The synthesizer is controlled by MIDI note messages, in the manner you’d expect: press a key
on your MIDI keyboard and Bitcom plays the corresponding note. Obviously you’ll need to route MIDI
messages to Bitcom in your host software in order to use this mode. Bitcom’s synthesizer is
monophonic and not velocity-sensitive.
Bitcom’s synthesizer certainly won’t win any awards for software synthesis. During Bitcom’s development we
used a simple tone generator as our input signal. As Bitcom came to life we discovered that mixing that tone
generator with other, more complex input signals produced sounds that didn’t happen when either signal was
processed by itself. Hence we gussied up the tone generator with an adjustable wave shape, an envelope
follower, and MIDI control, and incorporated it into Bitcom itself.
Level Controls
Finally, at the lower right of Bitcom’s window, we find the humble but essential level controls. The OUT knob,
at the far right, should be self-explanatory: it sets the overall output level of Bitcom. It has a maximum gain
of 0dB, i.e. unity, because you’ll almost always find that you need to make Bitcom quieter rather than louder.
To its left is the MIX knob, which controls the balance between the unprocessed input signal and the signal
created by Bitcom. Its setting is expressed as a percentage, where 0% means you hear only the unprocessed
input signal, 100% means you hear the signal after its destruction at Bitcom’s hands, and e.g. 50% means
you hear an equal amount of both. The 100% setting will present Bitcom’s true glory, but other settings are
useful. Setting the MIX knob to a small percentage mixes in just a little bit of the damaged signal, which can
provide a subtle but interesting texture.
The TO FX knob is essentially an input gain control. It changes the
level of the input signal before Bitcom crunches it. It has a range of
-24dB to +24dB, meaning a fair amount of attenuation to a fair
amount of boost. Since Bitcom’s effects on a signal depend heavily
on the amplitude of the signal, you may find that simply twiddling
the TO FX knob changes Bitcom’s overall sound dramatically.
The buttons under the CONTROL header aren’t level controls as
such, but this seemed like a good place to put them. Clicking the RND BITS button randomizes all of the BITS
switches, turning them either on or off with equal probability. Clicking the CLR BITS buttons clears (zeros) all
of those switches, zeroing Bitcom’s output. You might find it useful if clicking the RND BITS button produces
somewhat too much cacophony for your current mood.
The BYPASS button at the bottom of the column is probably also self-explanatory: if you turn it on, Bitcom’s
processing, and synthesizer, are bypassed altogether and you’ll hear only the input signal (if present).
Automation
All of Bitcom’s parameters can be automated using your host's automation features. Consult your host's
documentation for information on how to use these features. Note that Bitcom’s RND BITS and CLR BITS
buttons broadcast automation data when they randomize or clear the BITS matrix. If you find unexpected
automation data in Bitcom’s track in your DAW, this might be where it’s coming from.
And Finally…
Thanks again for purchasing Bitcom. We make every effort to ensure your satisfaction with our products, and
want you to be happy with your purchase. Please write info@audiodamage.com if you have any questions or
comments.
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