M-Audio Microphone manual Tubes vs. solid state, Tube electronics

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 harmonicClassdistortionA has more to do with the

associated circuitry than with tubes versus solid state. circuitry (where all amplifying componentsClassh ndleB the entire signal waveform) tends to produce lower-order harmonics. On the

other hand, (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

Choosing & Using Microphones 9