User guide

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“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.
4. Transparency: A good preamp should sound natural with no edginess. Tube preamps
sound warm, yet wonderfully transparent. Transformer coupled preamps sound punchy.
When recording with condenser or dynamic microphones engineers often choose mic
preamps that help “warm up the mic”, but warming the signal up does not need to be a
consideration with ribbon mics because they are by nature warm and realistic sounding.
At this point personal taste should prevail over anything.
Stereo Microphones and Ground Loops
Some preamplifiers are prone to developing ground loops when used in conjunction with