Manley MONO & DUAL MONO 40 dB MICROPHONE PREAMPLIFIERS - Manual (Page 8)

OPERATIONAL NOTES
8
SWITCHING ON
Allow this unit a few minutes for the tubes to warm up before use. It is not recommended that you
leave your preamplifier permanently switched on. This only wastes electricity and tube life. Your
preamplifier has solid state rectification and reaches peak operating condition in approximately 30
minutes.
TUBE LIFE
As with all tubes, their quality degrades with age. This is due to cathode emission, a natural process
found in all tubes. We recommend that you have your preamplifier checked every 4-5 years,
depending on usage, usually the preamplifier will require re-tubing after this time has elapsed.
Increased noise is usually a sign that the tubes need replacing.
OPERATION
The Microphone Preamplifier is equipped with a switchable 48 Volt phantom supply. Pull
the toggle to turn phantom power on or off. You should only turn phantom power on once you have
a solid state(FET) condensor mic plugged in and patched through to the Mic Pre and the monitor
volume is way down or off. DO NOT use phantom with an unbalanced source or valuable ribbon
mics. Damage to the Mic or preamp may result. Do not change mics or mic patches with phantom
power on especially if the monitors are up. See page 6.
The 40 dB Microphone Preamplifier is equipped with five preset GAINs, 40, 42.5, 45, 47.5
and 50 dB. These "numbers" are only if the ATTENUATE control is turned to full. This is not a pad.
GAIN sets the amount of negative feedback used in the Mic Pre. These preset gains affect tonal
quality, noise and linearity characteristics. At lower gains (40 dB setting) the Pre Amp has a very
clean quality, in some ways like solid state and is the best at minimizing tube hiss. 45 is a "normal"
setting because it tends to sound most like the source, and is very musical and real. The lower settings
can sound slightly slower, further back and more mellow by comparison. The 50 dB setting uses
almost no feedback and can give a slightly more punchy and forward or aggressive sound. It may
be a little "hot" (more than simply warm) for some tastes. Experiment to discover your own
descriptions. You will likely find a few settings that you prefer for your style of music.
The INPUT ATTENUATE controls the amount of signal entering the amplifier circuit. Use
this control to adjust the level of the input signal. It has no effect on the tonal quality and simply sets
the level sent to tape. Use the tape machine's meters to optimise levels.
The PHASE SWITCH can reverse the polarity of the mic signal. The middle position is used
for the 1/4" DIRECT INPUT and de-selects the mic input transformer. Reversing the polarity or
phase is often needed when two or more mics are picking up the same source. For example it would
be needed when one mics the top and bottom of a snare - one skin is going towards one mic and the
other skin is going away from the other mic. If one signal is not "reversed" then you lose lows.
Polarity reverse can also help with some vocal / mic / headphone situations because " somewhere
" the polarity flipped one too many times. It happens. General advise - try it each way - listen, with
vocals always ask the singer which way they prefer. The headphones may "cancel" with the sound
they hear in their skull while singing.