INPUT 1
VOLUME
MIC
PRIORITY
LINE
VOLUME
VOLUME
INPUT 2
VOLUME
INPUT 3
VOLUME
INPUT SELECT
MASTER
VOLUME
SYSTEM TONE CONTROLS
LOW
LOW MID
HIGH MID
HIGH
ON
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POWER
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U.S.Audio
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CONNECTIONS
POWER AMPLIFIER
STEREO/RECEIVER
MIXER
CASSETTE DECK
TELEVISION
CD/DVD PLAYER
TELEPHONE
JUKE BOX
MICROPHONE
1. PRIORITY MIC VOLUME CONTROL
varies the amount of the page mic signal
that is applied to the master output of the unit. As shipped from the factory, the mic
input is connected as Priority 1 which will override any other signal going through
the mixer when it is activated. Turning the volume off does not affect the priority
trigger, so leaving the page mic on with volume off could turn the system off
unexpectedly.
2. PRIORITY LINE VOLUME CONTROL
varies the amount of the priority line level
signal that is applied to the master output of the unit. As shipped from the factory,
the line input is connected as Priority 2 which will override the normal signal inputs
when it is activated, but not the Priority 1 mic input. Turning the volume off does not
affect the priority trigger, so leaving the volume off could mute the normal signal
unexpectedly, resulting in no audio passing through.
3. INPUT VOLUME CONTROLS
vary the amount of stereo input signal applied to
the master outputs through the select switches.
4. INPUT SELECT SWITCHES
connect the signal from the inputs to the master
output.
5. MASTER VOLUME CONTROL
sets the final overall volume of the MPM1
sources. All inputs and the remote volume control are affected by this output level
control.
6. SYSTEM TONE CONTROLS
allow changing the tonality of a sound system
using the four band controls. The LOW and HIGH are bass and treble shelving
filters. The LO MID and HI MID are peaking filters set at 250 Hz and 1.6 kHz.
7. POWER SWITCH
turns on the MPM1 power and illuminates the LED power
indicator.
8. PAGING MIC INPUT
is a female XLR jack which accepts balanced mic level
signals and feeds them to the priority audio circuits and to the priority override
threshold detector. 18 VDC phantom power is automatically supplied for condenser
microphones.
9. DUCKING LEVEL SWITCH
sets the amount of volume reduction when the
paging mic is in use
. In the 0 position, the normal signal and the page mic are mixed
together with no change in the normal signal level. At -20 the normal signal is
reduced by 20 dB and at -70 the normal signal is effectively turned off leaving only
the page mic audio signal.
10. REMOTE LEVEL CONNECTION
allows connection of a 10 k Ohm linear pot kit,
whirlwind
part # MPM1RV, to control the overall level of the MPM1 from a remote
location. V+ is supply voltage to the full counter clockwise terminal. VC is control
voltage from the wiper of the pot and G is ground.
11. LINE PRIORITY INPUT
is balanced TRS ¼” which accepts stereo or mono
line level signals and feeds them to the priority audio circuits and to the priority
override threshold detector.
12. INPUT JACKS 1,2
and
3
are stereo RCA unbalanced inputs which feed signal
to the front panel volume controls and switches. The MPM1V provides composite
video RCA inputs in addition to the audio inputs.
13. BUSS INPUT JACKS
are stereo RCA unbalanced inputs which insert signal
directly on the audio sum buss of the mixer. The Priority circuits and the Master
Volume control this input.
14. UNBALANCED LINE OUTPUT JACKS
are stereo RCA jacks that always
provide a stereo master output signal regardless of the position of the stereo mono
switch. The MPM1V composite video RCA output is also located here.
15. STEREO MONO OUTPUT SELECT SWITCH
feeds mono signal to both
balanced outputs when Mono is engaged.
16. BALANCED OUTPUT JACKS
are male XLR, with pin 2 positive, that deliver the
master output signal to the sound system amplifiers. Signal is line level and can be
stereo or mono.
17. EARTH LIFT SWITCH
disconnects the AC chassis ground from the audio
common and is sometimes useful in reducing hum.
CONTROLS AND FUNCTIONS
THEORY OF OPERATION
Both the MPM1V and the MPM1 have three stereo RCA
inputs, each with a front panel volume control and a pushbutton on/off
select switch. These inputs serve as the normal signal inputs, usually
used for music or program sources. They can be set at a
predetermined level and then conveniently switched in and out to
change the audio source (e.g. switching from VCR to tuner). The gain
range of the level controls is from -60 to +20 dB allowing their use with
a wide variety of audio inputs. There is also a buss input designed to
receive signals from other outboard sources such as DJ or live sound
mixers. There is no volume control for this input. Level can be adjusted
with the master volume control or by varying the output of the source
unit. Inputs 1-3 and the buss input (stereo) are summed and passed
through a series of Voltage Controlled Amplifiers (VCAs) and summing
amplifiers which comprise the priority circuitry.
The MPM1V has three RCA composite video inputs, which
are switched in conjunction with the three audio inputs. The selected
video input is delivered to a single RCA video output jack and the
unselected inputs are terminated with 75 Ohm resistors.
Both mixers have two priority override inputs each with
distinct features to provide capabilities for microphone paging and
injecting signals into the audio chain (e.g. emergency announcements
or a jukebox). There are two separate priority control circuits and the
unit is shipped with the mic input as priority 1 and the stereo line input
being priority 2. There are 6 user changeable jumpers inside which
reverse the connections of the priority 1 and priority 2 control and
audio circuits. All 6 jumpers must be moved to accomplish this. The
intent of this feature is to give the stereo line input highest priority
(priority 1) for emergency announcements and other such
applications.
A set of jumpers in the left channel VCA control circuit
provides another feature of the MPM1V and MPM1. Moving the
jumpers on priority 1 and priority 2 disables the ducking of the left
channel of the mixer. The audio signal from the priority inputs still goes
through to the left output and can be disconnected by removing
jumpers P1L and P2L. This arrangement provides the right channel
with ducking for paging and the left channel for audio program only
from RCA inputs 1-3.
The three normal program inputs and the buss input have no
priority status, so they will be active as long as there is no audio signal
present at the mic input (priority 1) or at the stereo balanced TRS line
inputs (priority 2).
When the priority line receives audio at its inputs, the priority 2
VCAs turn off channels 1-3 and the buss input. The priority line audio
signal is then injected into the audio path.
When the priority mic receives audio at its input, the priority 1
VCAs turn down the priority 2 input, channels 1-3 and the buss input to
a level that is preset by the ducking level selector. The priority mic
audio signal is then injected into the priority 1 sum amps.
The priority line inputs are left and right stereo TRS ¼”jacks
which accept balanced TRS or TS unbalanced signal. A mono TRS or
TS signal connected to the left input is normalled to the right and with
nothing plugged in, the inputs are shorted to ground. The stereo signal
is split to feed the detector of the voltage control circuit and to the
priority line stereo volume control which has a range of -60 to +20 dB,
allowing level adjustment of most audio outputs. The audio signal then
passes through the headers to the sum amplifiers.
The priority line volume pot does not affect the signal applied
to the detector control circuit. Since the volume control can be turned
down enough to be off, it is possible to mute the normal program music
by having signal present at the priority line input, but not hear it
because the volume control is turned all the way down. When using the
line priority input, the idle noise level (like a jukebox with no music
playing) must be well below the fixed detector threshold of -20 dB to
prevent false triggering.
There is a circuit board jumper in the detector circuit, which
sets the release time of the priority line input. This switches the decay
time from Normal (music is back to full volume in 3 seconds) to Slow
(takes 30 seconds for music to be back to full volume).
The priority mic input is a female XLR connector which accepts
balanced mic level signals and provides 18 volt phantom power for
condenser microphones. The signal passes through a 120 Hz high
pass filter which removes frequencies associated with rumble and
handling noise and is split to feed the detector of the voltage control
circuit and to the priority mic volume control which has a range of -40 to
+45 dB, allowing level adjustment of most microphones. The audio
signal then passes through the headers to the sum amplifiers.
The mic priority control circuit has two extra features; the
detector is controlled by a ducking level switch and remote VC
terminal. The ducking level controls the amount of volume decrease in
the program material during pages and can be user set at -20, 0 or -70
dB. At -20 dB of ducking, the program signal will be turned down but
will still be audible during pages. At -70 dB the background music will
be silent during pages. At 0 dB the normal program audio will not
change in volume during pages.
The volume control does not affect the signal level applied to the
override detector. If the priority mic volume control is turned all the way
down, the background music level will still be affected by speaking into
the mic if ducking level is set to -20 or -70, but the microphone will not
be heard. The detector threshold is fixed at -40 dB. A normal speaking
voice will engage the priority circuit with most microphones. The page
mic must have an on/off switch so that background noises will not false
trigger the detector when not in use.
The remote volume control feature of the MPM1 allows the overall
program level of the sound system to be adjusted from a location other
than the mixer. It is part of the priority mic voltage control detector
circuit, but is independent of the operation of the paging mic. With the
mic input connected to priority 1, the remote volume controls all inputs
to the MPM1 except the priority mic paging input. With the mic input
connected to priority 2, the remote volume controls everything except
the priority line input. Wired to the priority 1 circuitry, the priority line
input is ideal for injecting emergency announcements into the system
at a preset level.
The remote volume control is accessed through a three position
header and screw terminal plug. The three screw terminals are V+
which is +18 VDC power, VC (voltage control) wired to the wiper of the
remote 10 k ohm linear potentiometer (or accepts any standard 5 or 10
volt VC) and ground (G). Whirlwind includes the remote volume
control mounted to a single gang wallplate part # MPM1RV.
From the final sum amplifiers all audio passes through a stereo 4
band equalizer. The bass and treble controls are shelving type filters
which enhance bass and treble on quality stereo systems. The low mid
frequency control peaks at 250 Hertz which enhances upper bass in
ceiling/wall mount type speakers. The high mid frequency control was
chosen at 1.6 K Hertz to enhance voice frequencies.
From the equalizer section the audio signal passes through the
stereo master volume control with a range of -60 to +20 dB, which is
sufficient to drive most power amplifiers. The master volume control is
after the remote volume circuit. When setting the maximum volume of
a sound system utilizing the remote VC, the remote must be turned up
all the way before adjusting the master for the desired maximum level.
The stereo output signal is actively split to the stereo RCA outputs
and stereo balanced XLR outputs. Maximum output level is +23 dB.
The RCA jacks are intended for connection to unbalanced stereo
systems using a common dual RCA cable. The balanced outputs are 3
pin male XLR. A stereo/mono switch changes only the XLR jacks (RCA
jacks are always stereo) to mono, for use in single channel ceiling
speaker and background music applications, etc. In the mono
configuration, the output level of the XLR jacks will drop 6 dB to
accommodate the 6 dB of gain common with in phase stereo material.
For unbalanced XLR outputs, use pin 2 as hot, pin 1 as ground and do
not connect pin 3.
The power supply section of the MPM1 uses two power
transformers and two sets of voltage regulators to keep operating
temperatures at a minimum, providing dependable, continuous
operation. Internal jumpers can be moved (soldering required) to
change the primary transformers from 120 volts AC to 230 volts AC.
The power on/off switch makes and breaks both hot and neutral of the
power line. A power LED illuminates when the unit is on, and a ground
lift switch (on the back panel) breaks the AC earth ground from the
MPM1's audio ground.
Revision 2.0
BALANCED OUTPUT
MONO
STEREO
LEFT
RIGHT
LINE OUT
: TO PREVENT ELECTRIC
SHOCK DO NOT REMOVE COVER. NO USER
SERVICEABLE PARTS INSIDE. REFER
SERVICING TO QUALIFIED SERVICE
PERSONNEL.
: TO REDUCE THE RISK OF
FIRE AND ELECTRIC SHOCK DO NOT EXPOSE
THIS EQUIPMENT TO ANY TYPE OF RAIN OR
CAUTION
ATTENTION
120 Vac at 60 Hz
230 Vac at 50 Hz
30 watts MAX
EARTH
LIFT
120 Vac at 60 Hz
230 Vac at 50 Hz
30 watts MAX
U.S. AUDIO . A DIVISION OF WHIRLWIND INC . ROCHESTER, NY USA
BUSS
1
2
3
INPUTS
V
V
V
V
R
L
R
L
R
L
R
L
R
L
LINE
R
M
O
N
O
L
DUCKING
LEVEL
REMOTE
LEVEL
G VC V+
PRIORITY
-20
-70
0
MIC
OFF
