MACKIE TT24 - Manual (Page 49)

Mackie TT24 Digital Live Console Owner’s Manual Addendum v1.7
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When the mic-pre-master turns up or down the gain or adjusts the pad, the mic-pre-slave
console with Mic Pre Gain Compensation enabled, automatically compensates by adjusting its
digital trim. For instance, if the mic-pre-master turns up the mic pre gain by 5 dB, the mic-
pre-slave’s digital trim gets turned down 5 dB. This works fi ne once things are up and running,
but it would be weird for initial setup; you may end up with some very strange settings on the
mic-pre-slave trims during initial setup as all of the mic gains are being turned up. For this
reason, the mic-pre-slave console can stop compensation during initial set up by disabling the
“Trim Compensate” button. When compensating, the console Trim V-Pot control fl ashes when
selected, and pressing the console Ctrl + TRIM toggles this selection.
Also, + or - 15 dB of trim might not be enough to compensate in all situations especially
because the pad requires 23 dB of compensation, therefore, the digital trim which normally
only allows +-15dB of trim control without a snake attached, changes to +-60 dB when a
snake is attached. Note that if the mic-pre-slave needs to compensate with more than +-15 dB
of digital trim, something is probably wrong in the gain structure somewhere.
Another complex issue arises when snapshots are used. Both the mic-pre-master and mic-
pre-slave console need to be able to use snapshots to recall gain settings.
The mic-pre-master console actually controls the Mic Pre Controls, so it can store and recall
these settings. Doing so will send the information to the mic-pre-slave console which will
compensate for these snapshot induced changes, just as it does when you manually adjusts
these parameters.
When the mic-pre-slave engineer recalls a snapshot, their goal is to have an absolute gain
stored in the snapshot recalled and applied to the input. But, since the mic-pre-slave console
cannot directly control the snake mic pres, it must calculate the compensated gain from the
snapshot (stored mic pre gain + pad + stored digital trim), and then adjust the digital trim to
achieve the same level of compensation with the current mic pre gain setting set by the mic-
pre-master.
For example, let us assume the mic-pre-master and mic-pre-slave are confi gured as shown in
the columns below:
Master Slave Before Slave
Snapshot Slave Recall
Gain 40 dB Na 45 dB Na
Pad Out Na Out Na
48v Out Na Out Na
Trim 0 dB -10 dB 0 dB 5 dB
Compensated Gain 40 dB 30 dB 45 dB 45 dB
The snake gain is set to 40 dB by the mic-pre-master console. The mic-pre-slave console
engineer has adjusted the trim to -10 dB giving a compensated gain to 30 dB into the
corresponding slave console channel. If the master were to increase the Gain in the snake,
the mic-pre-slave would decrease the digital trim by the same amount. The mic-pre-slave
snapshot (which could have been created when the console was a mic-pre-master or mic-
pre-slave – see below) has 45 dB of compensated Gain through the mic pre and digital trim.
Since the current state of the snake mic pre is 40 dB, to achieve 45 dB of compensated gain,
the mic-pre-slave console must adjust the digital trim to 5 dB as shown in the Slave Recall
column.