Royer Labs SF-12 - Manual (Page 5)

performance can we expect from the preamplifiers built into our mixing desks? While most
preamplifiers will handle ribbon microphones well in most recording situations, some preamps
that work perfectly well with condenser or dynamic mics may prove to be poor performers with
ribbons.
To begin with, we must understand the fundamental differences between ribbon microphones and
other popular types, namely condenser and moving coil dynamics. A ribbon microphone is
actually a dynamic microphone that uses a flat, extremely low mass ribbon element, rather than a
coil/diaphragm assembly. For this writing, any mention of “dynamic” microphones will relate to
moving coil dynamics.
All condenser microphones have a built in preamplifier called a head amp and therefore put out a
hefty signal. Because the signal is buffered through the head amp, the output impedance is rather
low and less affected by the input impedance of the microphone preamp. Most dynamic (moving
coil) microphones generate a healthy enough electrical current to work well with a variety of
preamps, and their limited frequency response characteristics make mic loading less of a
concern.
Ribbon microphones generate a highly accurate signal, but the average ribbon mic generates
approximately 20dB less gain than that of condenser microphones. Remember, the ribbon
transducer does not have the benefit of a condenser mic’s built in head amp, so a ribbon
microphone relies solely on the microphone preamp for all its gain!
The so called ideal preamplifier is the proverbial “straight wire with gain.” This may be
considered the technological ideal and does not include “coloration” as a desirable feature.
However, coloration is often desirable and has given rise to the popularity of certain preamps and
even preamp stages in mixing desks. Neve® preamps and the famous Trident® A Range mixing
console are highly praised for their classic sound.
So what should we use with our beloved ribbon microphones?
The features that translate into top performance for a ribbon microphone are the following:
1. Lots of gain! A ribbon microphone works best with preamplifiers that have at least 60-70 dB
of maximum gain.
2. Low noise is a must! With this much gain being required for efficient operation of a ribbon
microphone, the noise characteristics of the preamp play a pivotal role in overall performance
of the captured acoustic event.
3. Load characteristics: A suitable preamplifier should have input characteristics that impose the
least amount of loading to the ribbon element. In other words, the input impedance should be
high enough that its effect on the performance of the mic is negligible. A good rule of thumb
is to have a preamplifier with input impedance at least five times the impedance of the
microphone. For example, if the mic is rated at 300 Ohms (as Royer’s are), the preamp
should have an input-impedance of at least 1500 Ohms. If the impedance of the preamp is
too low, the microphone will lose low end and body.
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