A microphone by itself is not very useful. To properly use a microphone, it needs to be connected to an audio device that will properly process its signal for recording and/or reproduction. The connections of microphones happen via plug and jacks.
What is the difference between a microphone plug and jack? A jack is a receptacle into which a plug is inserted. A mic jack is a female-type connector in a mic or mic cable. A mic plug is a male connector that is inserted into the jack. The XLR output of a professional mic is a mic plug. A mic preamplifier input is considered a mic jack.
Let's talk more about the different mic plugs and jacks, and microphones signal flow in general in this article.
Be sure to check out My New Microphone's article How Do Microphones Work? (The Ultimate Illustrated Guide)!
Related article: How Do Headphone Jacks And Plugs Work? (+ Wiring Diagrams).
Microphone Plugs And Microphone Jacks
Let's start by defining what the prefix microphone represents when speaking of microphone plugs and jacks.
From a strict terminology standpoint, it could be argued that there is really only such thing as a microphone plug. Microphones output audio signals, and their connectors (whether XLR, TRS, or otherwise) are plug-style male connectors.
We see this as the XLR output plug on professional microphones (as shown in the Shure SM57 pictured below).
We also see a microphone plug as the phone connector plugs at the end of built-in mic cables (as shown as a 3.5 mm TRRS on the pictured Rode SmartLav+). There are other connector types that portray microphone plugs, though XLR and phone connectors are the most common.
So microphones themselves only have connector plugs. But what about the inputs we plug microphones into? These mic inputs (for example, the pictured mic inputs of the True Systems Precision 8 preamplifier) are often considered microphone jacks. These mic inputs could also be of the phone connector variety (or any other mic connection type).
And what about microphone cables? Though XLR mic cables are not often thought of as having mic plugs or jacks, it could be argued that they do. In fact, any connectors that carry a mic signal could be considered either mic jacks or mic plugs. I've included a photo of two ends of an XLR mic cable to illustrate the microphone jack and microphone plug.
I think it's important to think of microphones as having more than just plugs. Thinking of mic inputs as mic jacks helps solidify the idea of a connection being made and microphone audio being sent/transferred to where it needs to go.
How Do Microphone Plugs And Jacks Work Together?
Microphone plugs and jacks of the same connector type connect together and allow electrical signals to pass from one to the other. But how exactly do they work together?
First, we must ensure the wiring of the jack and plug are compatible. XLRs are phone connectors are standardized with the following wiring (in both jacks and plugs):
- Pin 1 = ground/shield
- Pin 2 = hot/positive polarity audio signal
- Pin 3 = cold/negative polarity audio signal
For more information on microphones and XLR connections and cables, check out my article Why Do Microphones Use XLR Cables?
Tip-Sleeve (TS) Phone Connection Wiring
- Tip = audio signal wire
- Sleeve = ground/audio signal return wire
Tip-Ring-Sleeve (TRS) Phone Connection Wiring
TRS is standardized but will act to carry audio in one of two ways: balanced mono (as with most microphones) or unbalanced stereo (as with most headphones). Ensuring that microphone signals are sent and received in the balanced TRS mic inputs is important. Similarly, sending headphone signals out of unbalanced stereo TRS headphone outputs is important.
Here is the wiring for TRS balanced mono (for microphones):
- Tip = hot/positive polarity audio signal
- Ring = cold/negative polarity audio signal
- Sleeve = ground/shield
Here is the wiring for TRS unbalanced stereo (for headphones):
- Tip = left channel audio signal
- Ring = right channel audio signal
- Sleeve = ground/audio signal return wire
The possible wiring schemes of Tip-Ring-Ring-Sleeve (TRRS) (and additional ring phone connections) produce conflicting wiring standards. When using microphones with TRRS, it's critical to connect them to compatible TRRS mic inputs for proper connection, signal transfer, and microphone powering.
Some other microphone connections are available (such as multi-pin circular mic connectors) but are, in large, not standardized. Microphones that use these connectors typically come with compatible equipment or adapters. We see this oftentimes with lavalier microphones and their wireless transmitters (a scenario where the aforementioned multi-pin circular mic connectors work particularly well).
Once we're certain that the wiring of the mic plug and mic jack are compatible, connecting the two is easy.
For XLR's (3-pin or otherwise), insert the plug (male connector) into the jack (female connector) so that the 3 pins are aligned. The XLR connectors are designed so that there is only one way to connect the pins together, which makes it easy.
The connection is even easier for phone connectors, though more thought must be put into determining if the connections are compatible. We'll take the aforementioned Rode SmartLav+, for example. Once we've established that the 3.5 mm jack is a properly wired TRRS (like that of the iPhone headphone jack, which uses the newer CTIA/AHJ wiring standard), we simply insert the TRRS plug into the TRRS jack.
When connected, there is an actual electrical connection between the wires of the plug and the jack, which allows for signal flow. This is why it's crucial to have wiring standards (pin 1 of the plug connects to pin 1 of the jack, the tip of the plug connects to the tip of the jack, and so on).
Signal Flow From Microphone Plugs To Microphone Jacks
Microphones react to sound waves and output electrical audio signals (AC voltages) through their output plugs (male XLR, phone, or other connectors). We say that signal flows out of a microphone. In other words, signals flow from the mic plug to a connected mic jack (often an XLR cable or a mic input phone jack).
When connecting a professional microphone with an XLR output to a microphone preamplifier, the signal flows from the microphone to the preamp via an XLR cable. In terms of passing through connections, the mic signal flow from the microphone plug (male) to the XLR cable jack (female) and then from the XLR cable plug (male) to the mic preamp input jack (female).
Note that, with microphones, the XLR plug (male connector) always sends signal to its connected XLR jack (female connector). This is how connections are designed, though it is possible to alter this design with adapters in special circumstances.
As for microphones that utilize phone connectors, multi-pin connectors, or otherwise, the mic cable is often part of the mic design. This makes it easy to connect the microphone properly, given the mic input is correctly wired.
Another common microphone connection is the USB as digital microphones continue to rise in popularity.
Due to the nature of the USB connection (regardless of the type), USB microphones will have USB output jacks rather than plugs. The USB cable, like phone connectors cables, will have two male ends (a plug on either end).
With USB mics, the digital data flows from the mic's output jack to the connected USB cable plug, through the USB cable, and from the USB cable plug at the other end to the connected USB computer jack.
For more information on analog and digital microphones, check out the following My New Microphone articles:
• Are Microphones Analog Or Digital Devices? (Mic Output Designs)
• How Do USB Microphones Work And How To Use Them
Sending Power Through Plug And Jack Connections
On top of audio signal flow (both analog and digital), some microphones require power transfer through their plug-jack connection in order to function.
For proper power transfer from a power source to a microphone, all the plug/jack connections must be compatible. Non-compatibility can lead to electrical shorting and improper power transfer or no power transfer at all. Even worse, incompatibility or poor wiring will potentially damage your microphones and other audio equipment.
This is yet another reason to ensure that your plugs, jacks, cables, and equipment are wired properly!
Is a microphone jack the same as a headphone jack? Microphone jacks and headphone jacks are not the same, though they may use the same connectors (TRS, XLR) or even be combined into the same connector (i.e., in headsets). Mic jacks are designed to receive mic signals from a mic plug. Headphone jacks are designed to send signals to a headphone plug.
Can you plug a microphone directly into a loudspeaker? A microphone can be effectively plugged directly into a loudspeaker if the speaker is powered/active (with a built-in amplifier) and mic input. In this scenario, the speaker's mic input is designed to accept the mic level signal and amplify it properly. This is not true for passive speakers.
Choosing the right microphone(s) for your applications and budget can be a challenging task. For this reason, I've created My New Microphone's Comprehensive Microphone Buyer's Guide. Check it out for help in determining your next microphone purchase.