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You’re now ready to establish the correct gain structure—the key to getting the best
performance from the TM300, or from any mixer, for that matter. This is a simple
procedure that ensures optimum input and output levels so that no unnecessary noise
(caused by too low a signal) or overload distortion (caused by too high a signal) is
created. Here’s a step-by-step description of how to do so:
a. With all connections made (as described in the previous section) but with
the power
off, bring all channel faders and the left-right stereo faders completely down (to their “∞”
setting).
b. Turn all channel Trim controls fully counterclockwise.
c. Place all channel equalizer knobs in their center detent “0” positions and turn off the
seven-band graphic master equalizer by setting the EQ On/Off switches to their “Off” (up)
position.
d. Set the Meter/Headphone Source switch up (to its “L/R” position); this will ensure that
the TM300 meter shows the continuous level of the Left/Right stereo output signal.
e. Turn all channel Aux Send knobs and the main section Aux Return knobs to their fully
counterclockwise (“∞”) position. Turn the main section Tape In and Rev To Aux 1 knobs
to their fully counterclockwise (“∞”) position.
f. Set both main section master Aux Send knobs to their “0” (2 o’clock) position.
g. Power up all devices connected to the TM300 channel line inputs and Aux Returns
and set their level controls to unity gain or, if there is no unity gain indicated on their
output control, to maximum. If you’ve got outboard effects processors connected to the
Aux Returns, make sure they are sending completely “wet” (processed) signal, with no
“dry” (unprocessed) signal mixed in.
h. If condenser microphones are connected to the TM300, turn on the Phantom switch.*
Finally, turn on the TM300’s main power.
i. Play an instrument connected to one of the TM300’s line inputs** and, while doing so,
raise the corresponding channel fader to the “0” position. You should see the segment
meter begin to move—adjust the input Trim control for that channel so that the “0”
segment lights frequently and the “+3” segment lights only occasionally. The Peak LED
for that channel should not flash at even the highest level input signals. If the incoming
signal seems too hot even with the input channel Trim all the way at its minimum setting,
you may need to lower the output level of the instrument, though this will rarely occur.
Conversely, if the signal is too low even with the Trim all the way up, something’s
definitely wrong: in all likelihood, the connecting audio cable is faulty.
j. Once you’ve set the optimum level in step (i) above, continue playing the instrument
and slowly raise the stereo left/right faders until you reach the desired listening level.
* CAUTION: Before turning phantom power on, be sure to verify that all connected
mic(s) and/or active DI boxes require 48 volts. Also, disconnect all other signal sources
(such as passive DI boxes) from the XLR mic jacks.
** If you’re using an instrument such as electric guitar or bass, connect it to the TM300
with a direct injection box to ensure correct impedance.
Setting the Correct Gain Structure
ENGLISH