Ribbon microphones, generally speaking, are the most natural-sounding microphones on the market. The precise transient response, amazing low-end response, and natural roll-off of high frequencies mean ribbon microphones “hear” very similar to how human ears hear. These microphones are expensive and fragile, and so caution should be taken with anything that may damage them, including phantom power!
So will phantom power damage a ribbon microphone? Yes. Phantom power (+48V) has the potential to damage ribbon mics. Passive ribbon mics may be damaged by hot patching or electrical outages while phantom power is engaged, or if +48V is sent through a miswired or impaired cable. Active ribbon mics, however, require and will not be damaged by+48V.
So ultimately, the answer is “it depends.” This article aims to clarify phantom power and how it works with ribbon microphones. I hope you’ll find this post informative!
Will Phantom Power Destroy My Ribbon Microphone?
Potentially, but probably not. In either case, it’s always best practice not to send phantom power to microphones that do not require it.
It’s a common myth that the application of phantom power will destroy ribbon microphones. I personally think it’s a good falsity to help keep the fragile ribbon microphones safe, but a falsity nonetheless.
If phantom power is properly engaged, the +48 V should not affect the ribbon diaphragm. However, voltage spikes associated with sudden connection or disconnection of phantom power will stretch or even blow out a ribbon diaphragm.
A damaged ribbon will decrease the microphone’s performance or even render the mic completely ineffective. The good news is the damaged microphone typically only needs a new ribbon. The bad news is repair costs can be upwards of $350 for modern microphones and even more for the repair of vintage models.
What Is Phantom Power?
It’s crucial to understand the force that could potentially destroy our ribbon microphones. So here is the definition of phantom power:
Phantom power is a DC voltage that provides the necessary power to certain audio devices. It’s is most notably utilized to charge the capsules and power the active electronics of condenser microphones. The reason for the name “phantom power” is that it travels silently through the same balanced cable that carries the balanced microphone audio signal. The lack of an obvious physical power supply lends itself well to the term “phantom.”
The majority of microphone preamps and mixing consoles have phantom power options of some sort. Often, phantom power is denoted by a +48 V button or switch. As you can imagine, phantom power may be sent accidentally to microphones that do not require it. It can also be left engaged as microphones are plugged and unplugged from the preamp and mixer inputs.
+48 volts is the professional standard for phantom power. However, 12-48 volts is generally an accepted range.
The 48 volts DC travels from a supply to a microphone through a balanced cable. Typically this is an XLR cable. TRS cables are also capable of carrying phantom power, though this is dangerous due to shorting issues (as we’ll discuss later).
For more info on phantom power and microphones, check out my article Do Microphones Need Phantom Power To Work Properly?
What Is Balanced Audio?
Balanced audio is a professional standard of sending audio signals from one device to another. Balanced audio utilizes one ground/shield wire and two wires to transport the audio signal: one to carry the audio signal and the other to carry the audio signal is opposite polarity. Balanced inputs utilize differential amplifiers to combine the differences between the two signal wires into a usable signal. Any interference or noise present in both audio wires is cancelled out by the balanced input!
Balanced audio cables have 3 pins (conductive wires and connections in the cable):
- Pin 1 is chassis ground/cable shield
- Pin 2 is “hot,” carrying the positive audio signal
- Pin 3 is “cold,” carrying the negative audio signal
Balanced cables carry the microphone signal by reversing the polarity of pin 3 relative to pin 2. It’s the same audio signal, only in opposite polarity. Pin 1 effectively shields the audio on pins 2 and 3 by capturing external interference noise and sending it to the ground.
When the audio carried by pins 2 and 3 reaches the preamp or mixer, a differential amplify reverses the opposite polarity signals and effectively sums them together. The differences between pins 2 and 3 are amplified while the similarities are cancelled out. This is known as common-mode rejection and is very effective in ridding of interference noise that is picked up by the cable.
Common mode rejection also allows for phantom powering to exist and function as it does. +48 volts DC (standard phantom power) is sent from the preamp or mixer to the microphone in order to power it. More specifically, 48 volts DC is sent equally on pins 2 and 3 (relative to pin 1).
The phantom power voltage (potential difference) between pins 2/3 relative to 1 provides the required power for phantom-powered microphones. Two capacitors within these microphones block the DC from appearing at their output.
Dynamic microphones (ribbon microphones are essentially dynamic) are typically “protected” from phantom reaching their capsules by their output transformers. These step-up transformers simultaneously amplify the AC voltage audio signal output while blocking any DC voltage from passing through.
To learn more about microphones and balanced audio, check out my article Do Microphones Output Balanced Or Unbalanced Audio?
How Can Phantom Power Damage A Ribbon Microphone?
The transformer in a typical passive ribbon microphone is good enough to safely block a steady DC voltage from passing through to the fragile ribbon diaphragm. The real issue is with transient spikes of voltage that may pass through the transformer and wreak havoc on the ribbon element. A big enough jolt or unevenness of phantom power can directly affect the diaphragm, causing stretching or even a blow out of the ribbon.
Here are the 4 main reasons engaged phantom power may damage a ribbon diaphragm:
- Miswired or otherwise impaired microphone cables
- Damaged connections
- Hot/Live patching
- Electric surges and outages
Miswired Or Otherwise Impaired Microphone Cables
Phantom power is designed as +48 volts DC sent through pins 2 and 3 of a balanced audio cable. The voltages in pins 2 and 3 are in reference to pin 1, which is ground.
Lethal issues arise when the cable is miswired. If pins 2 or 3 are miswired as pin 1 in a cable, the supply voltage may get straight to the ribbon element. This will cause damage to the ribbon diaphragm.
If pin 1 is shorted to pin 2 and/or 3, a similar situation can happen where phantom power is sent through to damage the ribbon.
To avoid this, ensure the use of the properly wired professional balanced cables. Also, keep your cables in good working condition and either replace or repair any cables suspected of being impaired.
Be careful when repairing cables yourself to solder the pins to their respective connections!
You can always test your cable by plugging it into a phantom power supply, engaging the supply, and applying a voltmeter between the pins at the other (unplugged) end of the cable. The voltage (potential difference) between pins should be as follows:
- Pin 2 to pin 1 = +48 volts
- Pin 3 to pin 2 = +48 volts
- Pin 3 to pin 2 = 0 volts
Alternatively, you can use bright eyes technology. Plug the other end of the cable into the bright eyes phantom checker. Different LEDs will light up depending on the situation. A green light means phantom power is being supplied correctly within ±4 volts of the standard +48 volts. Any other colour of light tells us either phantom power is not supplied correctly or there’s an issue with the cable.
Alternatively, connections could be damaged. Connections may be faulty at the microphone input, either or both ends of the cable, or at the preamp/mixer input.
These connections are typically XLR and can be damaged through trauma or simply wear out over time and use. Once again, it’s always best to replace a connection you suspect to be broken.
It’s dangerous to have an incomplete connection when sending phantom power due to the high probability of a short circuit.
Patch bays provide an excellent hub for mixing and matching signal flows within a studio. With a patch bay, we have the ability to send various microphone signals through to different preamps and inputs if we would like to. This simplifies audio setups by reducing the number of cable runs and the changing of cable runs to reroute audio signals.
Patch bays typically come with sets of two rows: one row is an input and the other is the output. We can route any input to any output simply!
However, patch bays most often use TRS (Tip/Ring/Sleeve) connections. TRS jacks are quite a bit smaller than XLR and have been the standard for patch systems since their invention (hence their alternative name “phone plugs”).
TRS carries balanced audio just like XLR:
- The tip is positive audio = Pin 2
- The ring is negative audio = Pin 3
- The sleeve is ground = Pin 1
For this reason, TRS can also carry phantom power. However, there’s a big issue with TRS that applies directly to hot patching.
When plugging in an XLR cable, all pins connect simultaneously or the ground (pin 1) makes the first connection, followed by the synchronous connections of pins 2 and 3. This manner of connecting a microphone to a preamp protects the microphone from electrical shorts between pins 2 and 3. The ground is also immediately available at the connection.
TRS, on the other hand, makes the three connections one at a time. Regardless of how fast we physically connect a TRS but inserting the plug into a jack, there will be electrical shorting. The TRS jack has corresponding Tip, Ring, and Sleeve that connects with the plug as it’s inserted, but the connections are not all made simultaneously.
- Plug Tip crosses Jack Sleeve and Jack Ring before it matches with Jack Tip.
- Plug Ring crosses Jack Sleeve before it matches with Jack Ring.
- Plug Sleeve matches with Jack Sleeve last and completes the entire connection.
Let’s say we’re patching a TRS cable in our patch bay to connect a preamp to a ribbon mic. If phantom power is engaged on the preamp, it will short as the TRS cable is being plugged in. And if a connection is being made to the ribbon mic, this short may very well blow damage the ribbon diaphragm.
Related reading on My New Microphone: What Is The Difference Between A Microphone Plug And Jack?
Electric Surges And Outages
Electrical surges, outages, and brown-outs will cause sharp disengagement of phantom power and large transient spikes as the power is restored.
The good news is modern preamps and mixing consoles typically have safety features to mitigate electrical surges and turn power on gently after an outage or brownout.
Conversely, older mixers and preamps often have unregulated supplies that will surge even when powered up properly. In these cases, even turning the audio device on while the +48 V button is engaged could blow out a ribbon microphone connected to it.
Once again, these surges will cause transient spikes with the potential to pass through the output transformer of the ribbon microphone and damage the diaphragm.
Uninterruptible power supplies can be used in the studio to help protect against power surges and outages. UPSs are featured in My New Microphone’s Top Must-Have Tools For Audio Recording/Mixing Studios.
Active Ribbons And Active Circuitry
Active ribbon mics actually need phantom power (or some other DC power source) to function properly. These microphones, therefore, are designed with proper protection from the dangers of phantom power.
Condenser microphones require phantom power to charge their capsules and run their circuitry. Active ribbon mics only require phantom power for their active circuitry. If the phantom power DC voltage was to reach the ribbon diaphragm, it would most likely cause irreversible damage. So although active ribbon mics require phantom, no ribbon diaphragm should ever be subjected to phantom power!
It’s always best practice to disengage phantom power when plugging and unplugging microphones!
Will phantom power damage my moving-coil dynamic microphone? No, phantom power will not damage moving-coil mics. The output transformer/passive circuitry of a dynamic mic will block any applied DC voltage from reaching the diaphragm. Moving-coil diaphragms are also robust enough to resist damage from DC transients and surges that may potentially affect them.
For more information on dynamic ribbon mics, check out my article Dynamic Ribbon Microphones: The In-Depth Guide.
Are active ribbon microphones better than passive ribbon microphones? It depends. The pros of active ribbon microphones are:
- Protection from (and need for) phantom power
- Higher output level
- Less reliance on preamp selection
- Consistency of sound
The main pro of the passive ribbon mic is its versatile sound when combined with various preamps.