Solid-state electronics are everywhere in our day-to-day lives. Chances are you’re reading this on a solid-state device. If you’re using the microphone within that device (cell phone, laptop, tablet, etc.), you’re using a solid-state microphone as well!
What Is A Solid-State Microphone? A solid-state microphone is an active mic (one that requires electrical power to function) that works with solid-state electronics. In other words, a microphone that has circuitry based on semiconductor devices such as transistors (FETs, JFETs, etc.), diodes, and integrated circuits.
In this article, we’ll discuss solid-state microphones in great detail and look at a variety of solid-state mic examples.
Solid-state microphones, as their name suggests, are designed with solid-state electronics.
The term solid-state (or FET, which stands for field-effect transistor) is often used to differentiate these active microphones from their active tube mic counterparts.
Solid-state microphones utilize transistors as impedance converters rather than vacuum tubes. The result is that solid-state mics are less expensive to manufacture; less fragile, and require less power than tube mics.
These mics work in the following way:
The microphone capsule (transducer) converts sound waves into electrical audio signals. However, these signals are often too low in level and too high in impedance.
Solid-state electronics take this relatively poor signal and turn it into a proper mic signal for the microphone’s output. They do so with transistor-based impedance converters and integrated circuits.
To learn more about the differences between solid-state and tube microphones, check out my article What Are The Differences Between Tube & FET Microphones?
For a complete rundown on how microphones work, check out my article How Do Microphones Work? (A Helpful Illustrated Guide).
Solid-state electronics effectively means “semiconductor electronics.”
So solid-state electronics include the following semiconductive electronic components:
Each of the above components includes many different subtypes. There’s a lot to know about each component and each component could have its own article.
That being said, let’s discuss each of the general solid-state electronic device types and their roles in solid-state microphones.
When we hear the term “diode,” we typically think of a simple vacuum tube but there are many solid-state diodes as well.
Tube microphones, however, utilize triode vacuum tubes (or tubes with more than 3 electrodes) as their impedance converters. Solid-state microphones, similarly, utilize transistors with at least 3 terminals as their impedance converters.
Solid-state diodes can still be used in solid-state microphones (in the internal circuitry) though they are not used as the primary impedance converter.
Transistors are semiconductor devices used to amplify or switch electronic signals and electrical power.
Though there are many types of transistors, MOS transistors are likely the best known. MOS transistors have been essential in the development of digital electronics for their binary on/off (1’s and 0’s) nature.
There are digital microphones on the market (analog microphones with built-in analog-to-digital converters) that rely on MOS transistors to effectively convert and output digital audio signals.
However, it is the field-effect transistor (FET) that is of particular importance for solid-state microphones.
FETs, and particularly JFETs (junction-gate field-effect transistors), act as impedance converters in solid-state microphones. It’s the FET technology that effectively moves microphone manufacturers away from vacuum tube electronics toward the less-expensive, more durable solid-state electronics.
To learn everything you need to know about microphones and transistors, check out my articles Do All Microphones Have Transformers And Transistors? (+ Mic Examples) and What Are FETs & What Is Their Role In Microphone Design?
Integrated Circuits (ICs)
An integrated circuit is a set of electronic circuits on a small, flat electronic chip of semiconductor material (typically silicon)
Many larger solid-state microphones have integrated circuits in their design to amplify and otherwise affect the signal before the signal is outputted from the microphone.
ICs often provide optional pads and high-pass filters in active microphones that have these options.
History Of Solid-State Microphones
The first solid-state electronic device was arguably invented circa 1904. This was a crude semiconductor diode known as the cat’s whisker detector.
That being said, solid-state electronics only rose to popularity with the first working transistor in 1947. The invention of the transistor, by Bell Laboratories, marked a giant step forward in the realm of electronics and technology in general.
As with most advances in technology, it took some time before the audio industry began to utilize solid-state tech. The first solid-state microphone was invented in 1965 by the German mic manufacturer Schoeps. This microphone was called the CMT 20.
The term “solid-state” comes from the fact that electricity flows through solids rather than gases (as was the case in vacuum tubes, which predated the solid-state transistor).
Since the invention of the transistor, many active microphones have been designed with solid-state technology rather than with vacuum tubes. Solid-state mics have the advantage of being cheaper to manufacture; relatively robust, and more easily powered.
For more on the history of microphones, check out my article Mic History: Who Invented Each Type Of Microphone And When?
Properly Powering Solid-State Microphones
Speaking of powering solid-state microphones, there are several ways in which solid-state mics can be powered. Solid-state microphones typically get the power they require from the following methods.
Phantom power is standardized as +48 volts DC that is supplied via the 2 audio lines of a balanced audio cable.
Phantom power is typically supplied by microphone preamps though there are also standalone phantom power supplies available on the market. Phantom power is generally supplied on pins 2 and 3 of an XLR cable (the positive and negative audio conductors, respectively).
Because of the way balanced cables work, the phantom power is effectively sent to the microphone without affecting the audio signal whatsoever.
For a complete explanation of microphone phantom power, check out my article What Is Phantom Power And How Does It Work With Microphones?
DC Biasing is a DC voltage (typically between 1.5 – 9 volts) that travels on a single audio conductor.
DC-Biasing is a popular method for supplying power to miniature unbalanced solid-state lavalier microphones. It is most often supplied by wireless lavalier transmitters (which are powered by batteries).
The relatively low voltages of DC-bias supplies reserves this powering method mostly to the tiny impedance converters (JFETs) of mini electret lav mics. These solid-state impedance converters do not need much power to function and so DC biasing is an appropriate method.
Some solid-state microphones operate on battery power. These mics typically have an option to power the microphone directly with one of the other techniques mentioned in this article.
T-Power (A-B power)
T-Power was one of the very first methods to power solid-state condenser microphones through their audio cables. Phantom power, which is much safer, has since replaced T-power as the standard microphone powering technique.
T-power applies 12 volts DC is through 180Ω resistors between the positive audio wire (pin 2) and the negative audio wire (pin 3). These 12 volts of potential difference across pins 2 and 3 could lead to high current across these pins which would likely cause permanent damage to dynamic and ribbon mics.
Plug-in-power (PiP) is a lesser-known method of powering solid-state microphones.
PiP is often used to power consumer-grade electret microphones designed to connect to consumer audio equipment such as portable recorders and computer sound cards.
It is a low-current source that supplies +5 volts DC. The current is sent through an unbalanced cable, using the sleeve/shield as a return.
PiP works similarly to DC-biasing in the fact that it works on an unbalanced line and is typically used only to power the impedance converters of microphones with low power requirements.
To learn more about microphone powering methods, check out my article Do Microphones Need Power To Function Properly?
Solid-State Microphone Examples
I always find it easier to learn about a certain microphone type by looking at examples. So let’s take a look at some solid-state microphone examples:
Neumann U 87 AI
The Neumann U 87 AI (link to check the price on Amazon) is an example of a solid-state “true” large-diaphragm condenser microphone.
The Neumann U 87 AI has a transistor-based impedance converter placed immediately after its externally-polarized capsule.
It also has integrated circuits that provide options for a high-pass filter and a pad.
Neumann is featured in the following My New Microphone articles:
• Top Best Microphone Brands You Should Know And Use
• Top Best Studio Monitor Brands You Should Know And Use
The DPA 4006A (link to check the price on Amazon) is an example of a solid-state small-diaphragm electret microphone.
The 4006A has a transistor-based impedance converter placed immediately after its electret mic capsule. It features an integrated circuit to further shape the audio signal before its output.
DPA is also featured in My New Microphone’s Top Best Microphone Brands You Should Know And Use.
The Sanken COS-11D (link to check the price on Amazon) is an example of a solid-state miniature lavalier microphone.
The Sanken COS-11D has a DC-bias-powered solid-state JFET impedance converter.
The Blue Yeti (link to check the price on Amazon) is an example of a solid-state USB (digital) microphone.
The Blue Yeti does not only have an impedance converter after its multiple diaphragms. It also requires solid-state technology in its analog-to-digital converter in order to properly output a digital audio signal.
Blue Microphones is another brand featured in My New Microphone’s Top Best Microphone Brands You Should Know And Use.
What is a tube microphone? A tube microphone is an active microphone that uses vacuum tube electronics (rather than solid-state electronics) to effectively amplify and convert the impedance of the mic capsule’s signal. Tube mics are known for their character, adding saturation to the mic signal. They also typically require external power supplies.
What is a condenser microphone? A condenser microphone is a type of active mic transducer that converts sound into audio via electrostatic principles. Condensers can be designed as either solid-state or with tube electronics and are generally more accurate and sensitive than dynamic mics.
To learn more about condenser mics and how they differ from dynamic mics, check out my article Differences Between Dynamic & Condenser Microphones.