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RECORDING TECHNIQUES |
November 25,
2001 "CHRISTMAS" ISSUE |
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ANALOG
vS.
DIGITAL
ROUTING
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BY DANIEL DENNIS
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When dealing with the differences between analog and digital recording consoles, the biggest difference in operation is routing.
Almost everything else on digital and analog consoles operates the same, regardless of the format
(as far as the engineer is concerned).
The EQ controls, Auxiliary sends and returns, panning, monitoring, mixing, etc,
have the same principles.
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DIGITAL ROUTING: |
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Just about all digital consoles these days are designed to operate with MDM (Modular Digital Multitrack) recorders. Examples of MDMs are Alesis ADAT and Tascam DA-88. The routing of these consoles are based on the 8-track recorder system. The Yamaha 02R, as an example, is an 8-buss console. To buss to tracks 1, 9, 17 and 25, one would send a signal to buss 1. For tracks 2, 10, 18, 26, buss 2. Etc., etc., etc.
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There are disadvantages to this system. If you wish to buss one signal to track 10 and a separate signal to track 18 at the same time, it becomes difficult. The Yamaha 02R does have a way to switch busses, but it is involved and it takes time to do. And when you reset your console, it reverts to the original configuration. The Tascam TM-D8000 (the other digital console we use in our program), doesn't have a way to switch the busses.
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The way to route two signals to two tracks that use the same buss is to route one (or both) using direct routing (the input is sent to the same number track). When using a limited buss console (any console that has less busses than tracks), the general rule is:
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Inputs for individual instruments routed to individual tracks should be put in the lowered number inputs and tracks. The one exception that should be looked for is to ensure any stereo pair of tracks are on common pairs (1&2 or 3&4 or 5&6, etc.).
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Plan your tracks ahead of time so that you use the minimum number of busses and you are not trying to use one buss for two different signals at the same time. |
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ANALOG ROUTING:
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Most analog consoles seen in the field these days are also limited buss consoles (Mackie 32-8, Behringer
Eurodesk MX9000, etc.). There are 8 busses, and also direct outputs. The one advantage to the analog setup is that individual signals can be routed through a patchbay
from direct outputs to any track. For example, the Behringer Eurodesk MX9000 console (an analog console that I have used and that I actually like) has 48 channels, 24 that can be used as inputs and 24 for tape returns. There are 24 direct outs on the console and 8 sub-groups (busses).
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shows how you would wire a 16 track setup, with the direct outs of the
Mackie 32-8 wired (through a patchbay) to the inputs of the machines and
the outputs wired to console inputs 17-32. |
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Figure 1 |
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For the MX9000 console that I set up for a client of mine, I connected the direct outs to the patchbay and normalized the patchbay to the analog inputs of the recorders. I then connected the analog outputs of the recorders to the inputs for channels 25-48. I also connected the 8 sub-group outputs to the patchbay. This allows each recorder
track to receive (normally) the direct outs of the console, but also allows patching of
any direct output or any buss to any track.
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BUSSES:
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The biggest disadvantage to analog routing is that analog busses add noise
and distortion. Any analog device added to a signal path will add noise.
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The one thing I stress to all students that I teach is the most important thing in the recording process is signal-to-noise ratio. You want the highest possible signal (without overload of course) and the least possible
noise and distortion. The direct outs of a console do not add noise - the signal is sent directly to the recorder without adding more analog devices.
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Therefore, my advice in setting up any analog console is to employ patchbays which allow connection of direct outs of any channel to any
track.
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There is another thing to watch for in employing busses (in either analog or digital) to send one signal to one track. Busses are designed
to allow for mixing signals into a stereo image. On consoles is a 3-dB difference between the signal panned center to a track
and the signal panned left or right. This is inherent design
in panpots.
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Signals should be recorded at the highest possible level without overload, which gives you more signal to work with in mixdown.
Full level is reached when the signal is panned to the left or right. When
routing one signal to one track using a buss, pan the signal sent to the buss,
left for odd tracks and right for even. This gives the highest possible
signal.
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