Manual-
The front panel switchable LOOP is for stereo devices only,
so consider which effects are connected where. Some proces-
sors, 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 24z 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", XLR 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, oscil-
lations, or other stray characters from your system is to tell you
to experiment. If you think lifting the ground on the MP 24z,
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. Occasion-
ally, 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 loudspeakers 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 manufacturers
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 con-
nected for optimum signal-to-noise, sometimes both, sometimes
none. The rule is: “Whatever works, works.”
MP 24z CONNECTION
Even though the system variations are limitless in most ap-
plications where the MP 24z is used, an installer must follow
some basic interconnect guidelines. Unfortunately, even though
the system and the primary components such as mixers, proces-
sors 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 24z, RCA connectors
will prevail with unbalanced lines thereto attached. It is recom-
mended, 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 Manual-9 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 24z is of the commercial variety sport-
ing 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 XLR
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 24z is
running longer than 10 feet (3 meters), 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 recording
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 Micro-
phone section. If you need to record the Mic, use the Unbalanced
Main Outputs, Zone Output, or the Booth Output with the
Booth Ducker circuit defeated. (If none of these are available, see
Service Information on page Manual-9 for internal jumper chang-
ing instructions.)
