Manley MONO & DUAL MONO 40 dB MICROPHONE PREAMPLIFIERS - Manual (Page 6)

CONNECTING YOUR PREAMPLIFIER
6
There are two inputs and two outputs for each channel on the Mic Preamplifier. You gener-
ally only have to use one input and one output per channel.
On the back panel are female XLR's labelled MIC INPUT A and MIC INPUT B. The signal
from the MICROPHONES get plugged in here. There are a few warnings and suggestions.
These connectors also "send" PHANTOM POWER to the mics. Some mics can be damaged
by the 48 volts of phantom power. A few dynamics and a few ribbon mics have been known
to "fry" when fed phantom power. The suggestion is to ALWAYS have PHANTOM
switched off when switching mics, cables, patches that involve mics etc. You ONLY use
phantom power for SOLID STATE CONDENSOR MICS. Tube mics, dynamic mics, ribbon
mics and battery powered mics should have phantom switched "off". This is true for all mic
pre's. With this MIC PRE you "PULL THE TOGGLE to SWITCH PHANTOM". It is a
locking toggle to prevent "accidents". The second great reason for not using phantom if you
don't have to is that - if you change a connection with phantom on, then the pre amp will be
fed a quick burst of 48 volts (when it normally is amplifying about a hundredth of a volt),
which can then be monitored - usually once. After you have replaced your speakers, you
have learned a valuable lesson about turning down the volume of the monitors before chang-
ing mics or mic patches. This is a good idea with phantom on or off. Consider a variation of
this - any mic connection just a little bit bad, it will be extra noisy with phantom turned on.
This goes for cables, patchbays, patch cords etc. Suggestion #2 - Avoid running mic signals
through patchbays. Some patchbays "ground" all the "sleeves" which can add a ground loop
into your delicate mic signal. Suggestion #3 - Set up the Mic Pre in the studio near the mic
and use a short mic cable. Why ? Microphones often have "light duty" line drivers and you
can lose an audible amount of signal in long cables. You can get the best fidelity by having
the Mic Pre close to the mic at the "cost" of having to walk into the studio to adjust a level
control. You also avoid almost all of that phantom power / patching problem because now
you are patching a line level signal only.
The MIC INPUT XLR PIN OUT is :
PIN 1 = GROUND
PIN 2 = HOT or positive going phase
PIN 3 = LOW or negative going phase
(provided that the PHASE SWITCH is set to "0˚")
There is a 1/4" (mono) jack on the front panel for plugging instruments in directly. It
is not quite the same thing as a "Direct Box" designed for guitar or bass but it works fine and
is remarkable with keyboards. The PHASE SWITCH should be set to the "DIRECT IN"
(middle) position when using this 1/4" jack or else the signal may be loaded down. The
Direct Input is always on and switching to the middle position disconnects the MIC input and
Mic transformer. Almost always the DIRECT IN sounds better in the middle position. Of
course, you can also use any "direct boxes" you may have with the mic input with either the
0˚ or 180˚ settings. Check whether it may need phantom power, otherwise leave it off !