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Manual-6

Booth Output with the Booth Ducker circuit defeated. (If
none of these are available, see SERVICE INFORMATION
on page Schematic-1 for instructions to change internal
jumper blocks.)

The front panel switchable LOOP is for stereo devices

only, so consider which effects are connected where. Some
processors, such as delays and reverbs, have only one mono
input and two outputs. This is accommodated automatically
by using the MONO Output of the MAIN EFFECTS LOOP.

The Zone Outputs and the Booth Outputs are the auto-

matic mono/stereo type. If mono is required, simply connect
only to the LEFT OUTPUT. Inserting a plug into the RIGHT
OUTPUT automatically renders it stereo. All of these Output
connectors are unbalanced. Attempting to run TRS balanced
on any of these results in an open leg on the receiving
component and causes problems.

This is a good place to discuss the problems encountered

in connecting the MP 24 to all of the different types of cables
and connectors that one finds when basing a system on
consumer goods (the pieces of equipment with the RCA
connectors), commercial audio products (¼", 3-pin balanced
etc.), and no telling what else. In consumer audio devices, one
rarely finds ground-lift capabilities, or any of the other hum
prevention devices normally provided on commercial
equipment. Chassis ground and signal ground are normally
the same thing, a situation which may cause problems when
the two species get on the same bus.

The best we can do to try to help you eliminate hum,

oscillations, or other stray characters from your system is to
tell you to experiment. If you think lifting the ground on the
MP 24, crossovers, equalizers or power amplifiers might help,
go ahead and try it. There is science involved in de-humming
a system, however it is sometimes faster to just experiment.
Occasionally, directly grounding the chassis of the mixer to
the power amplifiers with a large gauge wire helps. And by
the same token, isolating the two when they are installed in
the same rack may have a quieting effect. A word of caution:
Don’t do anything with Level controls up, power on, or under
any condition that could cause damage to delicate loudspeak-
ers and ears.
 Make your changes with the system off, then
power up carefully to make sure you haven’t made matters
worse. Bring up Level controls slowly and with great caution.
Surprises are nice on birthdays and Christmas, and rarely any
other time.

If hum problems only exist on the Phono Inputs, there is

always a possibility for experimental troubleshooting at this
end also. Experience has shown that just because the manu-
facturers put ground wires on them, they are not always
connected! Some turntables even have two ground wires, one
for the tone arm and one for the chassis. Sometimes only one
of these should be connected for optimum signal-to-noise,
sometimes both, sometimes none. The rule is: “Whatever
works, works.”

SYSTEM CONNECTION

Even though the system variations are limitless in most

applications where the MP 24 is used, an installer must follow
some basic interconnect guidelines. Unfortunately, even
though the system and the primary components such as
mixers, processors and amplifiers are of commercial grade,
most of the source components, i.e. turntables, disc players,
tape decks and so on are consumer grade, with consumer
interconnect limitations. Therefore, on the input side of the
MP 24, RCA connectors will prevail with unbalanced lines
thereto attached. It is recommended, for no scientific reason,
that the turntable furthest to the left be connected to Phono 1,
and proceed from left to right with Phono 2 and then Phono 3,
if used. See SERVICE INFORMATION on page Schematic-1
to convert any PHONO level Input into a LINE level Input.

When determining which Line Inputs to use for what, the

process becomes a bit more difficult. Obviously, if one of the
line devices feeding the MP 24 is of the commercial variety
sporting balanced outputs, use Line 2 for this due to its
unique ability to accept such foreign substances. The rest of
the assignments are pretty much a matter of what you want to
appear where on the source switches. As you can see, Lines 1
through 3 appear only on Input Channels 1 and 2; Lines 4
through 6 appear only on Input Channels 3 and 4. So the
layout will depend on how heavily you will use the Phono
Inputs and how many line level devices you will be using.

On the Output side, things are a bit less restrictive. On the

MAIN OUTPUTS you have been given a choice between
3-pin balanced and ¼" unbalanced. Which you use should be
derived from some consideration of how far the cable has to
run from the mixer to the next component, how much ambient
noise there is in the local atmosphere (Radio Moscow in the
next building, 36,000 SCR controlled light dimmers in the
next rack), and any other possible encumbrance on the quality
of the audio inside the jacket. Most experienced installers and
users of commercial sound equipment have a good handle on
which to use in a given situation. The general rule is: if the
Output from the MP 24 is running longer than 10 feet, use
balanced cables. If the input to your system equalizer,
crossover, or power amplifier is balanced, go balanced. If
you keep the cable length short and your destination has
unbalanced inputs, you can probably get away with using the
¼" unbalanced connectors.

The TAPE OUTPUTS are unbalanced RCA connectors;

the assumption being that most readily available tape record-
ing equipment such as would be used in a club situation
would be of similar type. Simply determine whether you want
the signal processing in the Effects Loops to have an effect on
the recording being made and connect the record inputs (left
and right) to the appropriate PRE-LOOP or POST-LOOP
TAPE OUTPUTS. These Tape Outputs do not contain any
signal from the Microphone section
. If you need to record the
Mic, use the Unbalanced Main Outputs, Zone Output, or the

Summary of Contents for MP 24

Page 1: ...7 It s just not something you do Trust us you don t want to make mistakes with this sucker So just this once please we highly recommend you read this entire manual front to back every single page every single word It will familiarize you with the many intricacies of the MP 24 not to mention all the nooks and crannies ...

Page 2: ...eft side of the Crossfader to any of the four Input Channels when the Crossfader is activated by its ENGAGE switch 7 Right hand CROSSFADE ASSIGN switch This four position rotary switch ASSIGNS the right side of the Crossfader to any of the four Input Channels when the Crossfader is activated by the ENGAGE switch 8 CROSSFADER This fader controls the Levels of any two Channels assigned to it by the ...

Page 3: ...ging this switch enables the Program Equalizer to function In the out position the Equalizer is bypassed 19 HEADPHONE LEVEL CONTROL Clockwise rotation of this rotary control increases the headphone drive level 20 HEADPHONE PAN CONTROL This rotary control serves two purposes in the STEREO mode it changes the relative levels of the Cue and Program mixed together in both earcups In the MONO mode it c...

Page 4: ...lanced and unbalanced MAIN OUTPUTS of the MP 24 as it is rotated CCW 6 METER SENSITIVITY ADJUST Clockwise rotation decreases the full scale sensitivity of the PEAK PROGRAM METER as indicated by the full scale voltage calibrations around the control 7 SYSTEM MONO STEREO switch Engaging this pushbutton converts all Outputs except tapes and loops to MONO regardless of the nature of the Input signals ...

Page 5: ...atic 1 When these jumpers are set to PHONO as shipped from the factory these Inputs should never be used for any other purpose due to the amount of gain and RIAA equalization present Any unused Phono Input should have the Phono Shorting Plug installed to prevent interference from an outside source Do not put any of the Phono Shorting Plugs into the Tape Out jacks as this will short all the Outputs...

Page 6: ...es none The rule is Whatever works works SYSTEM CONNECTION Even though the system variations are limitless in most applications where the MP 24 is used an installer must follow some basic interconnect guidelines Unfortunately even though the system and the primary components such as mixers processors and amplifiers are of commercial grade most of the source components i e turntables disc players t...

Page 7: ...dB In the in position this range is reduced to 4 dB The latter is considered safer in situations where taste makes waste in drivers that is THE HEADPHONE CONTROL CUE SYSTEM To use the HEADPHONE CUE System signal must be present at one of the Inputs Well at least you do to make sure it works Depressing the CUE switch for the respective Input Channel presents this signal to the Headphone Cue amplifi...

Page 8: ... mic is heard from the Zone Outputs along with any Program EQ changes This can be changed with an internal jumper block The BOOTH OUTPUT operates much the same way with an added feature When the ENGAGE MIC switch is activated the gain of the BOOTH OUTPUT ducks down 13 5 dB to prevent feedback from the booth speakers If this Output is used for something else and this feature is undesired a BOOTH DU...

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