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Phone Gain
BK-1632 STEREO MIXER
21.
PHONE GAIN
The PHONE GAIN control sets the level at the
HEADPHONE jack. Any signal selected by
depressing a PFL switch will be monitored through
the headphone jack. With no PFL switch depress¬
ed, the headphone circuit monitors the left and right
sub outputs in stereo.
2J.
METER ASSIGNMENT SWITCH
A push-push switch is provided to allow the user
to select the points in the circuit which are
monitored by the LED VU indicators. When the
switch is depressed, the indication will be the audio
level at the left sub and right sub outputs. In the
other (non-depressed) position, signal level at the
main and monitor outputs will be shown.
2K.
LED VU INDICATORS
A vertical row of ten light-emitting diodes is used
to indicate signal level at selected points in the
circuit (see assignment switch). This type of display
is free from overshoot (ballistic) problems of
mechanical meters, and is highly visible under poor
lighting conditions. Each indicator is calibrated in
volume units, such that 0 dB corresponds to an out¬
put of 1.23 volts, which is +4 dBu, a standard in
the industry. The mixer provides 16 dB of
headroom above this level for superior sound
reproduction. It may be necessary in some cases
to reduce the sensitivity of equipment fed by the
mixer, such as a power amplifier, to prevent over¬
driving it. A gain control on the amplifier is usually
provided for this purpose.
•
2L.
SUBGROUP INSERT JACK
This jack provides a convenient point to add signal
processing devices lo the complete left/right
submaster mix. The jack is wired the same as the
channel insert jacks. The output can drive 600 ohms
or greater unbalanced loads up to +20 dBu and
the inputs can accept +20 dBu before clipping.
2M. LAMP CONNECTOR
A BNC type socket is provided on the right hand
side of the mixer panel to accommodate a Littlite'
gooseneck lamp, and allow operation of the board
under dark conditions. The 18-inch long "G" series
is available from many professional sound dealers,
and attaches without tools. The voltage at the
socket is 12.6 V ac at a maximum of 0.2 amps.
2N.
POWER SWITCH
The power switch is used to turn on and off the ac
main power.
20. POWER INDICATOR
This LED is illuminated when the ac main power
is on.
2P.
PHANTOM POWER SWITCH
This switch turns on and off the phantom power
supply. The phantom power supply provides power
for condenser-type microphones through the
microphone cable. When switched on, it produces
48 volts dc (with 3.4 K-ohm source impedance) at
pins 2 and 3 on all of the microphone input connec¬
tors. Pin 1 (the shield conductor) provides the ground
return path. This will power standard condenser
microphones and will not affect most dynamic
microphones. When switched on or off, the voltage
will ramp slowly up or down; it takes a few seconds
to reach full level. This prevents unwanted transients
from reaching the microphone inputs.
20.
PHANTOM POWER INDICATOR
This LED indicates when phantom power is present
at the microphone inputs.
SECTION 3.0
3.0
REAR PANEL INPUT CONNECTORS (Figure 3)
The BK-1632 mixer can accept program material covering
a dynamic range of over lOOdB. Exceptforthe high gain
mic input all of the line inputs can safely accept signals at
least up to + 20 dBu. (See Specifications for details).
Several of the inputs that directly access the mix buses can
be used to stack mixers together without using up an input
channel The stacking group includes the AUX, EFX and
MONITOR inputs. The EFX RET input may be used as
another stacking input. For stereo subgroup stacking set
EFX PAN to L and AUX PAN to R, and use EFX RET and
AUX IN for left and right stacking, respectively.
3A.
BALANCED LOW-Z MIC INPUT
A 3-pin XLR-type ("Cannon") connector is used for
balanced low impedance microphone inputs. The
Mic Input is actively balanced; active balancing
allows elimination of the input transformer (along with
its limitations) while maintaining the RF and hum
rejection of a good transformer coupled input.
It is important that, during operation or testing of the
mixer, all channel faders remain fully down whenever
the mic input is not properly terminated with a
microphone or equivalent 150-ohm source. An open
mic invites the introduction of high noise levels which
could produce lower quality sound or an incorrect
test measurement.
3B.
HIGH-Z LINE INPUT
A standard Vi-inch phone jack is used for balanced
or unbalanced line level signals. Examples of line
level signals include most electronic keyboards,
synthesizers, turntables (with appropriate preamps),
tape decks and the line outputs from other mixers. All
input channel controls, including the variable GAIN
control, affect the LINE input Maximum input level
before preamp clipping is 12 V or + 24 dB.
If a sufficient signal level is not possible with the GAIN
control in its furthest clockwise position, the input
signal must then be treated as a mic level signal, and
connected to the microphone input. If necessary, use
an appropriate balancing transformer (EV Model
502CP or equivalent) or a direct box with the
microphone (XLR) input.
eight
'Littlite is a trademark of C.A.E., Hamburg, Ml
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