When studying microphones and audio, the topic of unbalanced and balanced audio is sure to come up. Unbalanced and balanced audio are the two common ways to send audio from one audio to another (from a microphone to a mic preamplifier, for example).
Do microphones output balanced or unbalanced audio? The vast majority of professional microphones output balanced audio. These are the mics with XLR output connections. However, some professional lavalier microphones and many consumer-grade mics output unbalanced audio.
Let’s explain balanced and unbalanced audio in more detail in this article and understand why some microphones output balanced audio while others output unbalanced audio.
Balanced Audio Vs. Unbalanced Audio
Before getting into balanced microphones and unbalanced microphones, let’s first define what balanced audio and unbalanced audio are.
What is unbalanced audio? Unbalanced audio is the term for any system that carries an analog audio signal with two conductive wires: one signal wire and one ground wire. The signal wire carries the audio signal while the ground wire provides grounding, shields the signal wire, and completes the circuit with the signal wire.
What is balanced audio? Balanced audio is term for any system that carries a mono analog signal with three conductive wires (positive polarity audio, negative polarity audio, and common ground). The two signal wires in balanced audio cancel each other out and require balanced inputs with differential amplifiers.
Now let’s get into each of these “systems” in more detail.
Understanding Unbalanced Audio
As mentioned, unbalanced audio utilizes two conductive wires to carry audio:
- Signal wire: Carries the audio signal.
- Ground/shield/signal return wire: Provides a return path for the audio signal, thereby completing the necessary electrical circuit for the audio signal. This wire also acts as a ground and an electromagnetic shield for the signal wire. Inside 2-wire unbalanced cables, the shield wire actually threads out and provides a protective shell around the signal wire along the length of the cable.
Unbalanced audio is carried by these two wires only. The audio signal is carried by the signal wire and is referenced to the ground wire.
The ground wire simultaneously shields the signal wire from electromagnetic interference (EMI) noise and acts as an antenna, which picks up EMI noise.
Any noise picked up by an unbalanced cable is subjected to the audio signal. The more noise the unbalanced line induces, the worse the signal-to-noise ratio of the audio signal.
This is particularly important for microphones since mic level signals are so low (often in the 10s of mV range). Microphones generally do not use unbalanced outputs for this reason.
For more information on microphones, mic level, and line level, check out my article Do Microphones Output Mic, Line, Or Instrument Level Signals?
For this reason, unbalanced lines are typically short (no more than 15-20 feet). When using unbalanced lines, it’s best to keep them as far away from noise sources as possible (especially power lines and cables). Try not to run unbalanced lines parallel to power cables it at all avoidable.
Microphone that utilize unbalanced outputs are typically lavalier or headset mics with short cable runs. These mics are usually position on a person and away from power cables.
Let’s run through some unbalanced connection examples:
- Tip-Sleeve (TS): In Tip-Sleeve (TS) connectors, the tip is signal wire and the sleeve is the ground wire.
- Unbalanced stereo Tip-Ring-Sleeve: Unbalanced stereo TRS has the unbalanced left audio channel on the tip, unbalanced right audio channel on the ring, and a common ground wire on the sleeve.
- Unbalanced mono Tip-Ring-Sleeve with DC bias: Some microphones (particularly lavaliers) require a DC bias voltage in order to function properly. TRS with DC bias has the tip as signal wire, ring as DC bias wire, and sleeve as ground wire.
- Tip-Ring-Ring-Sleeve (OMTP standard): This “old” standard carried unbalanced mic signal with the following wiring: Tip is for unbalanced headphone right audio channel, Ring 1 is for unbalanced headphone right audio channel, Ring 2 is for unbalanced microphone audio, and Sleeve is for ground.
- Tip-Ring-Ring-Sleeve (CTIA/AHJ standard): This “new” standard carries unbalanced mic signal with the following wiring: Tip is for unbalanced headphone right audio channel, Ring 1 is for unbalanced headphone right audio channel, Ring 2 is for ground, and Sleeve is for unbalanced microphone audio.
- RCA: RCA has an inner pin that carries the audio signal and an outer shield that acts as the ground/shield/signal return wire.
As we can see from the above examples, audio connector with more than 2 connections are not necessarily capable or carrying balanced microphone audio. In fact, most aren’t wired to do so.
Understanding Balanced Audio
As mentioned, balanced audio utilizes three conductive wires to carry audio:
- Ground/shield wire: The ground/shield wire provides a reference point for each of the signal wires and may connect to ground at a connection to an audio device. This wire also acts as a cable shield, protecting the intertwined signal wires from electromagnetic interference.
- Positive polarity signal wire: The positive signal wire carries a copy of the audio signal in positive polarity.
- Negative polarity signal wire: The negative signal wire carries a copy of the audio signal in negative polarity.
So balanced audio requires three wires to function properly. The same signal is present in positive polarity on the hot/positive wire and negative polarity on the cold/negative wire. Each signal wire is referenced to a third wire that acts as a common ground.
The ground wire simultaneously shields the signal wires from EMI noise and acts as an antenna, which picks up EMI noise. Overall, the insulation and ground/shield wire reduce the amount of noise that is transferred to each of the signal wires.
A common design feature of balanced cables is the interweaving of the two signal wires into what is known as a twisted pair. A twisted pair of signal wires makes the induced noise more even between the two signal wires.
So basically what ends up happening is the two signal wires end up with equal amounts of signal interference noise in the same polarity, but the signals are are in opposite polarity.
When the balanced line is sent to a balanced input, a differential amplifier sums the differences between the two signal wires. This rids of the noise (which is the same on each wire) and adds the signals together (which are completely “out-of-phase” with one another). This process is known as common-mode rejection.
With common-mode rejection, we may run long balanced audio lines with little degradation in the audio signal. Mic level signals are very low and profit tremendously from clean signal transfer in balanced scenarios.
Therefore, professional microphones typically use balanced audio!
Let’s run through some balanced connection examples:
- 3-pin XLR: In XLR connectors, which are the standard for carrying balanced microphone audio, pin 1 is the ground wire, pin 2 is the positive audio wire, and pin 3 is the negative audio wire.
- Balanced Tip-Ring-Sleeve: In the balanced mono version of TRS, which isn’t very common for microphones (though XLR-balanced TRS adapters do exist), tip is the positive audio wire, ring is the negative audio wire, and sleeve is the ground wire.
As we can see, there are fewer balanced line options for microphone signals.
XLR is by far the most common balanced connection for microphones and is found in most professional mics. The balanced mono TRS cable can carry balanced audio, but is not designed to carry phantom power properly and so is rarely ever used with microphones. Exercise caution when using XLR-to-TRS or TRS-to-XLR adapters with your microphones.
For more information on microphones and XLR connections and cables, check out my article Why Do Microphones Use XLR Cables?
Microphones That Output Balanced Audio Signals
The vast majority of professional studio and live reinforcement microphones output balanced audio. If a microphone has an XLR output connector, it outputs balanced audio.
For example, the Shure SM57 dynamic and Rode NT1-A condenser microphones (pictured below) output balanced audio via XLR.
Microphones with XLR outputs will output balanced audio. Microphones with other types of connectors will generally output unbalanced audio signals.
Shure and Rode are featured in My New Microphone’s Top 11 Best Microphone Brands You Should Know And Use.
Microphones That Output Unbalanced Audio Signals
Even though phone connectors, multi-pin circular connectors, and other non-XLR microphone connectors have enough conductive wires to be wired as balanced cables, very rarely are they actually balanced.
Microphones that use phone connectors (TS/Tip-Sleeve, TRS/Tip-Ring-Sleeve, TRRS/Tip-Ring-Ring-Sleeve) are generally all unbalanced, even though TRS and TRRS have enough conductive wires to be wried as balanced lines.
Similarly, multi-pin circular microphone connectors cannot be guaranteed to be balanced and typically are not.
There are two main reasons why microphone TRS, TRRS, and other connectors with three or more conductive pins are unbalanced:
- Wiring standards: Microphone connections are often subject to standardization, which may dictate whether or not a connection may pass balanced audio or not. For example, the CTIA/AHJ wiring standard has TRRS connections wired as the following: T=unbalanced left channel headphone audio, R1=unbalanced right channel headphone audio, R2=ground, S=unbalanced mic audio. So when designing a microphone to properly connect to a TRRS jack (Rode SmartLav+ for example), it’s only possible to send unbalanced mic audio (via Sleeve and Ring 2).
- Power requirements: Sometimes standards are ignored in the name of microphone specific needs. Many lavaliers and their compatible wireless transmitters use unbalanced connections with more than 2 conductive wires. Two wires (mic and ground) are used to carry the audio signal while another wire is used to carry a specific DC bias voltage to power the specific microphone.
Basically any microphone that does not output via XLR can be (safely or not) assumed as being unbalanced.
Are all XLR cables balanced? Although the common 3-pin XLR cable (used to connect pro microphones and audio equipment) is designed to carry balanced audio, not all XLRs are strictly balanced cables. XLR connectors vary from 3 to 7-pin designs and are often wired to carry both balanced and unbalanced signals simultaneously.
Are USB microphones balanced or unbalanced? USB microphones output digital data and are therefore neither balanced or unbalanced. Balanced/unbalanced audio refers to analog audio signals. That being said, the capsule(s) of USB mics do initially output analog audio (which is typically balanced) before converting it to digital data.
For more information on analog and digital microphones, check out my article Are Microphones Analog Or Digital Devices? (Mic Output Designs).