Speck Electronics SSM - Manual (Page 29)

Chapter 4 Operation Section
A yellow LED to the right of this switch will illuminate indicating the
Mono status of operation.
When the Model SSM is configured with mono input channels, this
switch acts as a Pre Fader Listen (PFL) Switch. Depressing this button
allows the selected channel's signal to be soloed (in mono) even if the
slide fader is down or the channel is muted.
The source for the PFL signal is post (after) the equalizer circuit so any
EQ changes will be reflected. As with the in-place solo circuit, PFL
feeds only the master monitor and/or headphone outputs as well as the
dedicated tuner output.
A red LED to the right of this switch, as well as the master Solo/PFL
LED will illuminate indicating its status.
Depressing this switch allows you to isolate any input channel to the
monitor and/or headphone outputs while maintaining stereo perspective.
This means that the Pan/Balance Control remains active, and any left/
right position set by the Pan/Balance Control to the stereo mix will be
maintained when the In-Place Solo Switch is depressed. The direct
outputs on each input channel also remain unaffected by the operation of
the solo switch.
The source of the solo signal is post (after) the channels equalization and
the slide fader control. When a solo switch is enabled, any adjustment
to the channels level control or equalization will be evident in the
monitor and/or headphone playback.
Any combination of input channels or effects returns may be soloed
without interrupting the flow of the signal to the program master feed.
A red LED to the right of this switch as well as the master Solo/PFL
indicator will illuminate if a channel is soloed.
Depressing this switch deletes only the channels dry signal from the
SSM's stereo mix but leaves the rest of the channels signal flow
(equalizer, effects sends, and direct outputs) intact. This allows you to
send a synth or sampler signal to any number of effects devices without
hearing the original signal.
Pre Fader Listen (PFL) Switch
10. In-Place Solo Switch
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11. Kill Switch