Manley MONO & DUAL MONO 40 dB MICROPHONE PREAMPLIFIERS - Manual (Page 7)

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This Mic Pre also has two outputs for each channel. One is balanced and one unbalanced.
The XLR is a true transformer balanced output. The 1/4" mono (tip -sleeve) jack is unbalanced
and gets its signal before the transformer.
The XLR PIN OUT is: The 1/4" PIN OUT is:
PIN 1 = CIRCUIT GROUND SLEEVE = CIRCUIT GROUND
PIN 2 = HOT or positive going phase TIP = SIGNAL
PIN 3 = LOW or negative going phase
(providing that the Phase Switch is set to 0˚ and there is no plug in the 1/4" output)
We used to only provide an unbalanced output and it fed both the XLR and 1/4". Now we
give you options. The purists amongst you will probably prefer the unbalanced output because
it goes through one less component and the purists demand that the signal gets forced through
the best and as few as possible (its one of the big reasons they chose the Manley Mic Pre). The
Studio Pro's will probably prefer the balanced output for two reasons. The first is that they require
the easiest patching and least hassle set-up with any situation they might encounter in any studio
they might be using. Transformer balanced outputs are easily the best solution. The second reason
is that they may like the "sound" of transformers. One well known engineer told us he "loves the
sound of great transformers and hates the sound of bad ones". These are great transformers -
because they have virtually no "sound" of their own. You can verify this by comparing the
outputs. We wind the transformers ourselves and we are probably the last or only audio
manufacturer doing so. We had to, to get the quality that we wanted.
If you read the PIN OUT carefully, you may have noticed we specified CIRCUIT
GROUND rather than just GROUND. We have a few terminals on the back panel for various
"ground schemes". The CIRCUIT GROUND is the same ground as the electronics in the Mic Pre
while the CHASSIS GROUND is the same as the steel enclosure that is bolted to the rack and
is connected to the "third pin AC Mains Ground. Both terminals are normally connected together
with a small "ground strap" but this strap can be moved to the side and wire can be attached to
the terminals. These are "MINI BANANA" style and will not accept regular size bananas found
on electronic test gear. Be careful with the ground strap because it can get lost if the terminals
are loose. If it does get lost - you can use a short bare wire.
There are two good reasons for using these ground terminals. The first is finding and
fixing hum and the second is preventing hum. If you have plugged everything in right and you
are getting hum then you have a number of options with these terminals. You can try simply
moving the strap so that chassis ground is separate from circuit ground. This is similar to breaking
off the third pin AC ground but includes the ground from rack mounting . One can experiment
with attaching a wire between the console ground and the circuit ground or between a rack and
the chassis ground. These are all techniques some technicians use when wiring studios. They also
often cut the ground (shield) on one side of the cable to prevent loops. DO NOT cut the shield
on MIC cables because you lose phantom, shielding at the mic, and hum only gets worse !
One other cause of hum - Some gear may radiate a field into whatever is closest. Move
the Mic Pre or the offender away from each other.