- 1 Phantom Power Definition
- 2 Phantom Power Supplied by Bose Systems
- 3 Phantom Power Connected to Bose Systems
- 4 Questions
Phantom Power Definition
Question: What is a "phantom powered" microphone? Does that mean that the microphone draws its power from a remote source?
Answer: Phantom power is used with condenser microphones. It is called phantom power because there is no obvious external power supply for the condenser mic; the power supply is invisible and therefore a "phantom." The mixer sends voltage up the same wires that the audio is traveling down. Thus, the microphone is receiving the power remotely from the mixer.
Phantom power is a DC voltage (usually 12-48 volts) used to power the electronics of a condenser microphone. For some (non-electret) condensers it may also be used to provide the polarizing voltage for the element itself. This voltage is supplied through the microphone cable by a mixer equipped with phantom power or by some type of in-line external source. The voltage is equal on Pin 2 and Pin 3 of a typical balanced, XLR-type connector. For a 48 volt phantom source, for example, Pin 2 is 48 VDC and Pin 3 is 48 VDC, both with respect to Pin 1 which is ground (shield).
Because the voltage is exactly the same on Pin 2 and Pin 3, phantom power will have no effect on balanced dynamic microphones: no current will flow since there is no voltage difference across the output. In fact, phantom power supplies have current limiting which will prevent damage to a dynamic microphone even if it is shorted or miswired. In general, balanced dynamic microphones can be connected to phantom powered mixer inputs with no problem.
Will Phantom Power Damage Dynamic Microphones
- Phantom power supplies have current limiting which will prevent damage to a dynamic microphone even if it is shorted or miswired. In general, balanced dynamic microphones can be connected to phantom powered mixer inputs with no problem.
- Source: What is Phantom Power, Shure.com
- As long as your mic cables are all wired properly (balanced, with the correct pin connections) and well made, and you are using decent XLRs everywhere — and all your microphones are modern — there is no problem at all.
Phantom Power Supplied by Bose Systems
Phantom Power Available
Phantom Power is available on
- L1® Classic / L1® Model I the Power Stand supplies 24 volts for Phantom Power.
- ToneMatch mixers provide 48 volts for Phantom Power.
Bose Phantom power supplies have current limiting which will prevent damage to the Bose device if the connected device attempts to draw too much current.
Turn Down Master Volume Before Turning on Phantom Power
- Please turn down the Master Volume control before turning on phantom power
This will avoid noise being sent out to the powered loudspeakers when you turn on the power.
No Phantom Power
There is no phantom available on
Phantom Power Connected to Bose Systems
You may want to connect your Bose Portable PA to an external system using the Line Out. All of the Line Outputs are line-level, balanced outputs. On the T1 ToneMatch Audio Engine, T4S, T8S, L1® Compact, the outputs are 1/4 inch (6.3mm). On the T8S, there are also XLR Outputs.
Will Phantom Power Damage Bose Outputs?
- Will phantom power provided by the external system damage the Bose Portable PA system?
The outputs of Bose Portable PA equipment have circuitry to protect them in case phantom power is turned on in the external system.
24V volt Phantom Power
That is a somewhat difficult topic. We certainly have tried a KMS105 for live and even for recording with our 24V phantom supply and didn't find any problems. Then again, everybody's ears and taste is a little different, so I can't claim that there really isn't any difference. Going through the Alesis might also change things a little, so it's hard to do an exact apples-to-apples comparison.
From a technical stand-point, it's difficult for me to believe that there are any issues. I haven't taken a KMS 105 apart yet (they ain't cheap !) but most Neuman mics use an internal DC to DC converter and polarize at 200V or so. If any, that should work better with a "proper" 24 V supply because it can provide nearly twice the overall power of a standard 48V supply. Getting more useable DC power was actually one of the reasons why the 24V standard was suggested.
Different microphones do different things with Phantom Power but it's not only the voltage that matters but also the current. The original 48V/6.8kOhm standard was optimized for microphones that needed external polarization and therefore high voltage but nearly no current at all. But this type of microphone is exceedingly rare these days and the phantom power is used either to drive an internal pre-amp or to run an internal voltage-converter or stabilizer. For both cases a supply with lower voltage and higher current (and more overall power) is actually better and hence the 24V/1.2kOhm standard was derived.
I hope I don't bore everybody to death with some math, but let's look at the example of the KMS105. I believe that at nominal 48 V the mic draws about 4mA. That current also goes through the internal 6.8k Ohm resistor of the phantom power supply and leads to voltage "sag". If we use Ohm's law we find that the internal effective resistance of the microphone is about 5 kOhms and that the voltage at the microphone terminals is only 20 V. All the rest is lost inside the supply. If you attach the same microphone to 24V/1.2kOhm supply the voltage sag is much less and the voltage at the microphone terminals comes out to be 19V. It's hard for me to believe that this 1 V difference should make any apprectiable difference in the mics performance.
For an even more power hungry microphone that draws 5mA, the 24V/1.2kOhm supply will actually provide 3 Volts MORE (17V vs. 14V) at the microphone terminals. Sounds a little counterintuitive, but is actually true.
Of course, in the end you have to be the judge of what sounds best to you ears.
Hope that helps
If you have questions about this article, please post a message in Phantom Power Discussion in the Bose Portable PA Community