Manley Langevin Dual Vocal Combo 1999 - 4/2001 LDVC000 - LDVC178 - Manual (Page 7)

MIC PRE BASICS
This Microphone Preamp, like most mic preamps, is pretty easy to use. First we can discuss
why outboard mic preamps have become “a must have item” in almost every studio even though
your console probably has a bunch of them and that manufacturer claims that they are really great
and you don’t need outboard mic preamps. Then, why is everybody buying them, using them, and
why are most people going back to tubes or vintage transistor based circuits?
Good question. The signal from a typical mic is very low - anywhere from 20 to 70 dB below
your normal line level signals. 95% of the time 30 to 40 dB of gain is all that is needed to boost the
signal to line levels. Where you really need a lot of gain is with most ribbon mics and when you are
recording chamber music from a distance. Mic signals are fragile and raw. The fragility is appar-
ent when one compares various mic preamps - each preamp seems to sound different - no EQ, no
compression, nothing elaborate - just basic gain. Maybe it is the mic reacting different into differ-
ent circuits. Each preamp, tube or solid state seems to impart a flavour or color (or personality) of
its own. Some of these flavours are subtle and some are not. A few engineers have an array of mic
preamps and use them almost like effects - using each for a certain flavor as needed. The rest of us
only have the budget for one or two great mic preamps so we tend to choose one that sounds “best”,
or is priced for us, or is used by “xxxxxx”. The Langevin Microphone Preamplifier is superb sound-
ing - probably because it has a simple all discrete gain stage with a minimum of components and a
minumum amount of negative feedback. Specifications, while important, will not be truly indicative
of an audio product’s “sound” until methods of determining the transient accuracy are established.
Transient accuracy is not a “spec” and test benches don’t produce hit records. The transient details
are important for reproducing the true character of the instrument, the room and stereo image. Most
solid state circuits use a large amont of negative feedback to lower noise and distortion at the cost of
transient accuracy. This preamplifier started out clean and quiet so minimal negative feedback was
necessary.
Op-amp based designs, by comparison, have dozens of transistors in each “chip” (its easier
to fabricate a transistor than a resistor on silicon), hundreds of dB’s of negative feedback and some-
times a few discrete transistors to provide performance that an “IC” simply cannot. The result is
good specs - but that harsh, hard, cold sound that makes shakers sound like pink noise, makes vocals
sibilant in an unpleasant way, and can only render a 2 dimensional image at best. We prefer tubes or
simple discrete circuits.
We mentioned mic signals are fragile and raw. Some consider that the “headroom” factor is the
most important issue in mic preamps. We believe that it is just one of a number of issues including
the harmonic character of the distortion. Except for the final output, all circuits are “Class A” which
is usually associated with zerocrossover distortion and near clipping will be even order distortion
and less upper harmonics.This Preamplifier has more headroom than most solid state mic preamps
because of the 48 volt power supply used, compared to 30 volts (+/- 15V or 24 volts) used in other
designs. If overdriven, which is not easy, it starts to clip in a gentle, smooth way.
Another consideration above and beyond technical concerns when it comes to the art of
recording music is that every preamp seems to have some comparative influence on the “sound”
of the mic signal. When we have a choice, we tend to use the preamp that either best flatters the
singer or instrument or gets closest to the desired final sonic goal. Sometimes, the choice is the
clean & pristene pre and sometimes it is the vintage or aggressive box but it seems to be getting
rarer that we choose the basic console mic preamps. The Dual Vocal Combo is typically considered
“clean but vintage” and not as “dry” as many all-discrete mic preamps. People have used the words
“smooth” and “strong” to describe it but undoubtedly you will find your own words to descibe it
compared to your console and other units.
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