M-Audio Microphone User Manual page 9

An output transformer and/or amplifier serves as a sort of translator and, in audio, we expect that
translation to be excellent in order to maintain frequency response, dynamic range, and
signal-to-noise ratio. Just as a professional language translator costs more than someone who just
took a few years of foreign language in high-school, pro-quality output transformers and amplifiers
cost more than garden-variety ones. (A single transformer like those used in each channel of pro
consoles and outboard preamps can cost more than a complete inexpensive multi-channel mixer.)
Because the quality of this formidable translation is so critical in a professional-quality microphone,
all M-Audio mics employ high-quality Class A electronics in the head amp.
Tubes vs. solid state
The head amp can employ either tube electronics or less expensive solid state electronics. Before
we can effectively compare these two technologies, it is important to understand some
fundamental concepts.There are three main ways to measure how accurately an electronic circuit
passes sound frequency response, total harmonic distortion (THD), and dynamic distortion.
Frequency response is the simplest to understand.We re simply talking about whether any highs or
lows are rolled off, or if any frequencies are cut or boosted to exhibit a non-linear frequency
response. Both tube and solid state electronics can be made without significant deficiencies in
frequency response.
Regarding THD, all electronics induce some kind of harmonic distortion, i.e. harmonics that are not
present in the original source. The nature of the harmonic distortion has more to do with the
associated circuitry than with tubes versus solid state. Class A circuitry (where all amplifying
components handle the entire signal waveform) tends to produce lower-order harmonics. On the
other hand, Class B (where the positive and negative parts of the waveform are amplified by two
separate devices) tend to produce higher-order harmonics. For this reason, Class A strikes most
people as sounding warmer. (All M-Audio mics employ Class A circuitry.)
That brings us to the third, more mysterious element called dynamic distortion something that
the industry didn t even have the technology to measure until quite recently. Dynamic distortion
refers to the accuracy or transparency over time, particularly critical regarding the transient at the
very beginning of a sound.Take the recording of a finger snap, for example.You can roll off the highs
and lows and/or introduce a good amount of distortion, yet still perceive the sound as a snapping
finger. Change the dynamic, however, and that snap can quickly lose its characteristic snap. In
general, accuracy in reproducing dynamics can make the difference between something sounding
full and three-dimensional or flat and two-dimensional.
Ironically, the discussion comes down to measuring things that don t matter and not measuring
things that do.Tubes measure greater in THD than solid state.While one can measure the difference
between .01 percent THD and .001 percent THD, it s practically impossible to hear that difference.
On the other hand, while it s difficult to measure dynamic distortion you can definitely hear it. Solid
state electronics exhibit many orders of magnitude more dynamic distortion than tubes. This is a
major reason why tube mics make recordings sound truer to life.
Tube electronics
Tubes cost more money to manufacture than comparable solid state electronic components. In fact, the
music industry is one of the few places where tubes have value in the face of more modern electronics.
It s a known fact that the average tube exhibits more inherent noise than solid state electronics. In
general, the smaller the tube, the better. Larger tubes have a greater propensity for being
microphonic, i.e. generating noise from mechanical movement of the internal parts. They also use
higher voltages that result in more heat and subsequently more noise. Most manufacturers tube
mics employ larger 12-volt tubes like the 12AX7 an older tube design that is noisier when used
in microphone design.
TIP: One of the first things to be aware of is that not all products advertised as being tube mics employ
tubes in the main signal path. Some popular low-cost mics utilize less expensive solid-state circuitry, putting
a tube in the side-chain. (You can literally cut the tube out of the circuit on some models and the mic will
9
Choosing & Using Microphones