Zen and the Art of Troubleshooting
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do not expect the user to understand every detail of each component.
The reality is for most of us, in the first stages of discovering these
components, the details can just be too overwhelming. The goal in the
beginning is to simply know what they are and basically what they do.
For example, know that Performer installs FreeMIDI or Studio Vision
installs OMS. FreeMIDI and OMS are MIDI operating components that manage
MIDI hardware drivers and MIDI information to and from your synths
and the software. Another example, DAE (Digidesign's audio engine) is
a digital audio signal-operating component that speaks between your
audio hardware and your sequencing software. These types of components
maintain settings and routings for MIDI and audio playback. It is also
important to know a little about the computer's hardware and operating
software (OS). The type of computer, processor, bus speed hard drive,
mother board and PCI/ISA expansion capability can give you insight on
the powers and limitations of the software components.
Signal flow is the
communication to and from your MIDI and audio hardware and the computer
software. The purpose of a sequencer is to trigger your determined MIDI
and audio events consistently within a time grid. There are two properties
of a sequencer's signal flow, a master signal and a MIDI trigger signal.
The foundation of a sequencer is the master signal flow of timebase
and address. Timebase is the rate of the sequence playback and address
is the location of events. MIDI trigger signals are bi-directional and
simultaneously flow to and from a source and target. MIDI trigger signals
are recorded within the timebase and address framework.
In a MIDI
and digital audio workstation, timebase is word clock. Digital audio
samples run on a clock rate for output signal, just as a tape is sped
across a tape head. This rate is measured in Kilohertz rates like 44.1kHz
or 48kHz. A MIDI and digital audio sequencer will derive the rate of
playback from the audio hardware's word clock.
is a master signal. You simply have to establish a master and configure
the slave devices to follow the signal chain. The simplest example of
this is connecting two DAT (Digital Audio Tape) machines to copy digital
audio to another tape. To use common digital audio terminology,
the first playback DAT machine is the source or master and the recording
machine is the target or slave machine. The master DAT machine sends
the sample data via word clock to the second target or slave DAT. You
must set the source or master DAT to generate the word clock rate. For
the target or slave DAT, you must have it's digital input button or
similar setting engaged. In a MIDI and Digital workstation, the concept
is the same. The hardware that determines the rate of your sequence
can be the master or a slave.
also a master signal. It determines where MIDI and audio play back within
the time line of your sequence. In a MIDI and digital audio workstation,
address is usually MIDI Timecode and is measured in SMPTE timehours,
minutes, seconds, and frames. As well, the placement of your hours,
minutes, seconds, and frames to be determined by the rate of the timebase,
so that a sample's placement has an address in time just as MIDI events
do. This is why timebase and address will generally need to be referenced
from the same master source if you wish your audio and MIDI to playback
at a consistent point in time together, in synchronization.
signal of a workstation is MIDI recording and playback. The most common
example is recording your keyboard performance into a MIDI track. You
play a keyboard; it records your performance into the sequencer, which
allows you to play the keyboard's sounds back to you. When recording
MIDI into a sequencer, a note on and off signal is sent to the MIDI
out. It then travels through your MIDI interface and is translated as
an event in the software. This signal in turn may be patched through
the software, back out through the MIDI interface and to a MIDI instrument
for playback. Though MIDI is serial, meaning these MIDI data travels
a series, one event after the other, the result will appear simultaneous.
Differing from master signals, MIDI trigger signals can be routed to
many different destinations, from many different sources simultaneously,
like a phone switchboard.
So this is
a MIDI and Digital Audio workstation in a nutshell. I purposely did
not cover details about your workstation in this writing. These words
are an attempt to help you see the forest for the trees, a way to focus
your thought process so you may discover the details on your own. Obviously,
a basic understanding of your components and their signal flow will
not always enlighten a solution. It will give you the power to pinpoint
simple problems. For more complex issues, it's a tool that helps you
communicate with troubleshooting professionals. Most important
of all, it instills a sense of control over the situation and the confidence
to work towards a solution.
2 of this two-part series will appear next Friday, Aug. 4. Daniel Cates
is currently a tech support technician for Mark of the Unicorn.