Front Panel
11
(9) Meter Function -
This three-position switch determines what the channel’s VU meter displays. In
the up (OUTPUT) position, it shows the final output level in dB. "0" on the VU meter corresponds to +4
dBu at the analog outputs and -16 dBFS at the A/D converter inputs. In the down (DRIVE) position, it
shows the input level to the tube stage after the front panel Gain control, but before the Blend and
Level controls, thus giving an accurate gauge of how hard the tube and solid-state preamplifiers are
being driven. In the center (GR) position, the meter displays the amount of gain reduction occurring in
the channel’s compressor if the COMP switch (
#13 below)
is engaged for the channel. If the
channel’s compressor is off, the meter will not deflect from zero when set to GR.
When the switch is in DRIVE mode, the meter is calibrated so that 0 VU is equal to 1.2% THD on a 1kHz
sine wave. When OUTPUT is selected, a meter reading of 0 VU corresponds to a level of +4 dBu at the
rear panel LINE OUTPUT jack.
(
See “Drive Metering” on page 25 for additional analog metering info
)
(10) Low Cut -
When enabled (placed in the up position), the channel’s input signal passes through a
75 Hz low cut filter. This is normally used to eliminate rumble and other unwanted low frequencies
from an incoming signal.
(
See page 21 for more information about low cut filtering
)
(11)
Polarity (“ø”)
-
Determines the polarity of the channel’s LINE OUTPUT
(
#8 on
page 16
) and
the polarity of the signal at the A/D converter inputs. When off (in the down, IN ø position), pin 2 of the
LINE OUTPUT is hot (positive). When the switch is enabled (in the up, OUT ø position), the output signal
is placed out of phase and pin 3 of its LINE OUTPUT is hot (positive). Normally the switch should be off
and only enabled when it is desirable to reverse the polarity, i.e., in cases where more than one
microphone is utilized in recording a source signal.
(
See page 21 for more information about polarity inversion
)
(12) Insert –
When enabled (placed in the up position), the input signal is routed through the chan-
nel’s insert jacks on the rear panel
(
“Insert Loop” on page 16
) for external processing. When
disengaged (in the down position), the signal at the return jack is ignored. The insert switch allows you
to leave external processors conveniently connected when you don’t want to currently use them on the
channel.
(13) Comp –
This three-position switch controls the channel’s 1176-style analog compressor. The
compressor has a compression ratio of 4:1 and the threshold is 10 dBu.
When in the up (FAST) position, the compressor attack time is 0.3 ms and the release time is 100 ms.
When in the down (SLOW) position, the attack time is 2.0 ms and the release time is 1100 ms.
If the METER FUNCTION switch
(
#9 above)
is set to GR, the amount of compressor gain reduction is
displayed in the METER.
>
The Send jack is active even when Insert is disengaged, so you can route the channel’s
signal to a monitor mix, tuner, etc.
