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Phantom microphone. What is phantom power for a microphone


Phantom power is the transmission of information signals and power through a wire at the same time. Basically, remote power is used if it is not possible to connect to a 220 V supply network. Recently, such a system is increasingly used to power security and telephone equipment. The phantom power supply can also be used successfully for connecting a microphone, keyboard, or electric guitar.

Depending on the method of supplying the supply voltage, there are two varieties of this system. In the first case, the supply voltage is supplied through a separately laid cable or unused conductors of trunk cables. In the second case, it is routed over the trunk cable along with the Ethernet signal. In this case, additional cable conductors are not used.

48V phantom power for the microphone is supplied over the signal wires. Capacitors in this case delimit the circuits of alternating and direct current... It should be noted that the use of power supply must be approached with utmost care, because in the case of commutation microphone input with an unbalanced signal source, an unexpected power-up can cause a breakdown of the device (for the simple reason that voltage will be applied to it).

Phantom power does not negatively affect balanced sources. If a keyboard or electric guitar is connected to it, then it is necessary to use switchgear, the task of which is to lower the supply voltage to the mark required by the connected device. It is also recommended that you ensure that the source to which the phantom power is connected does not power other devices that require higher amperage.

If we consider this phenomenon from a technological point of view, then phantom power is a rather convenient way to save copper, but only too often in practice various unpleasant situations arise. It is necessary to use a high quality separator filter, otherwise the supply voltage may enter the signal circuits, and noise from the switching power supply circuits may penetrate the receiver input, or the signal may be attenuated in the power filters.

At first glance, everything may seem quite simple and straightforward, but this is by no means the case. The point is that the filter's task is not only to separate the DC and AC components. Therefore, it also needs to be broadband. The wide bandwidth filter should not distort the waveform. So that the acceptable link length does not decrease significantly, it should not lead to noticeable attenuation.

If we consider the practical application of remote power supply, then it is worth noting that two adapters must be used on the P296 cable. That is, there must be an adapter at each end of the link. They must have separate power and information inputs. Experiments confirm: if adapters are used for the UTP5 cable, then when all cores of the cable are used to transmit power, the range of the central power supply will almost double.

I needed a phantom power supply to connect the condenser microphone to the camera. The question is: WHY? Then, that the fotik writes the sound much better than the built-in sound card of the computer, and the condenser microphone simply already existed.
Budget external sound cards still almost all require additional phantom power. And those that do not require fall out of my budget. So I decided to try to order such a source.



When a microphone is connected to the camera through it, there are no problems, everything works clearly, everything is clear, it is recorded. However, first of all, I decided to disassemble this interesting box.

The case is interesting in that you can buy it separately for your electronic needs. Another issue is the price, it is not very cheap. Up to three printed circuit boards can be placed inside such a housing. A wonderful straight thing, if not for the price)

Inside the block of phantom power supply of a budget PCB, and the board itself is also very budgetary. However, no interference is observed at the output during operation, in any case, such interference that I could measure with my multimeter. The output voltage is + 47V instead of +48, ​​I don't think it's so critical. In any case, everything works as expected.
By the way, I tried to connect to the GoPro Hero 2 camera, the sound it writes is very mediocre. In fact, sound recording is not her primary task, but she copes with the primary tasks with a bang.


We see a bunch electrolytic capacitors an unknown Chinese manufacturer. In any case, such a manufacturer is not known to me, but in my work I come across capacitor manufacturers very often.

Well, the transistor also turned out to be a little not soldered, I fixed this matter.


By the way, about the transistor and why it is not attached either to the radiator or to the case. Half an hour gave the handkerchief to work by controlling the temperature of the transistor. So it almost never warmed up in a closed case, the situation will be tougher, but I think its temperature will definitely not even come close to the maximum permissible.
By the way, it is worth noting that the power supply of this device is transformer, 18V, 600mA.

If anyone is too lazy to read, then all the same is in the video and in addition, you can evaluate the quality of the recording through this phantom power unit. The recording quality was compared when recording through the power supply and through the built-in microphone of the camera.

I plan to buy +4 Add to favourites I liked the review +10 +13

Many who design sound equipment (in particular, preamplifiers), for sure, in some design required phantom power unit... In addition to using such a block as part of the structure(for example, a power supply for a mixing console), less often this unit may be required and as an independent design... So, for example, musicians using condenser microphones asked me to make such a unit, and even with an appropriate adapter for connecting a microphone to an active speaker or a mixer without a built-in phantom power unit.
In general, the design is nowhere simpler. Yes, you need good stabilization and good noise filtering, which, in general, linear stabilizers like LM317 do well. The single most important problem is where to get enough AC voltage(not less than 32V)? Transformers over 24V, it seems, are not in short supply, but a very specific thing that will not always be at hand.
Here comes to the rescue voltage multiplier on capacitors and diodes. The scheme has long been known and very widespread, almost everyone has heard about it, for sure. And who has not heard - Google to help :)
I will not dwell on the multiplier separately. I will clarify only one feature - a diode multiplier impractical use on high currents load. But, since standard consumers of phantom power are ultra-low-power, such a solution is just perfect for them.

Let's dwell on a multiplier by 4. Indeed, finding a 12-15 volt transformer is as easy as shelling pears. There is another reason for choosing a multiplier by 4 - this is the presence of a point common for entry and exit, which is just a minus. And this is also a serious advantage. So, multipliers built according to other possible schemes (including with other multipliers) must be powered from a separate winding or transformer as shown in the picture below Option I... This is due to the fact that in common circuitry, the negative output of the converter is connected to the zero point of the common power supply (total mass), and the combination of the input and output of the multiplier at this common point, or even more so, their connection through another winding will lead to its failure ( breakdown of diodes).
This multiplier can be switched on according to the scheme under option II, which means - significantly simplify the design and save money on the transformer.

So let's take a look at the diagram below. Everything in it is more than simple. The aforementioned multiplier, common zero, LM317 regulator, included in the standard circuit. Zener diode VD2 added to protect the chip from maximum allowable voltage drop between input and output (according to the documentation - 35V). Indeed, such a drop can be short-lived - at the moment of charging the capacitor C7 or in the case of too incorrect setting of the value of R5 (the latter is unlikely). At this moment, the zener diode shunts the microcircuit, thus protecting it from failure. The reverse voltage of the zener diode should be no more than 35V, but at the same time not too small to maintain a sufficient range for adjustment and stabilization. Especially for cases where the transformer outputs more than 12V. Then you can set the desired value of the output voltage of the stabilizer (48V in our case) using R5. By the way, I would not recommend supplying an alternating voltage of more than 20V.


Let's consider it in more detail. C1 - C4 and VD1-VD4 in this case form a voltage multiplier by 4. After them we have provided double filtering - to reduce the background.
First there is, in fact, a second order filter on R1C5 and R2C6, then an active filter / stabilizer on LM317. And after the microcircuit - necessarily - the capacitor C7, which prevents self-excitation of the circuit. In early modifications of the circuit without this capacitor, there was often a strong noise in the power supply and instantly disappeared if a capacitor was connected to the output or the load was of a capacitive nature.
The trimmer resistor R5 is set output voltage... Recommendations for setting it up are at the end of the article. R3, R4 and R5 we recommend using powerful (0.25W, 0.5W), because in some cases they will heat up.
We also recommend paying attention to VD6. If the circuit is powered by a separate transformer (or a separate winding), there is no need for it and it can be replaced with a jumper. However, if the circuit is powered from one of the transformer windings of a bipolar power supply, or another stabilizer is powered from the same winding, the diode is necessary to protect against a short circuit of the diode in the circuit of another rectifier connected to the same winding when the signal ground is connected. Why this short circuit can occur, which can lead to failure of the rectifier, and how the diode solves this problem, is shown in the diagram below.

And here is a modified circuit for using the power supply as a stand-alone device. The standard is provided here. connecting a device that needs phantom power... It is fed through limiting resistors R6 and R7 to the signal contacts of the device (for standard condenser microphones with XLR connector, these are pins 2 and 3, 1 is common), and the signal is directly fed through the blocking capacitors C8 and C9 to the receiving device ( mixer, amplifier, sound card).

Also for you ready - developed and tested printed circuit board... Layout - above, below you will find a link to the file in the format Sprint Layout and Gerber if you want to make your own boards. You also can order from us a ready-made factory printed circuit board and even the assembled device ... To do this, contact us through the contact form!

  • Attention! Additional information on this scheme on user questions!

    Many who gathered this device according to the multiplier circuit by 4, they complain about the background power supply.
    Therefore, I consider it necessary to pay attention to the following: scheme is necessary adjust the circuit with the trimmer R4 so that the background is minimal and the voltage is maximal! A linear regulator works as a filter if a voltage drops across it, commensurate with the amplitude of the ripple. I deliberately did not set the exact value of the divider resistors, which select the output voltage in order to be able to adjust the circuit for different transformers (from 10V to 16V). The condenser microphone is not so critical to the power supply as to achieve exactly 48V. Therefore, if the transformer you have chosen does not produce a voltage sufficient for the normal operation of the circuit, an output voltage of at least 37V will be acceptable.

    • Happy assembly everyone!

    The further, the more funds appear for improving computer devices, which, for one reason or another, are slightly below the required level. In many cases, this is not a software solution, but independent devices that enhance one or another aspect of the functioning of, for example, a microphone.

    What is phantom power for a microphone

    In particular, we are talking about additional food, which is commonly called phantom. Whatever the linguistic constructions, this is a device that will add energy to the suffering device immediately as much as 48 V.

    Traditionally, all new and unusual devices are bought on AliExpress and sent to the customer by mail. The latter has to understand what he has in his hands and why it is needed.

    Here is a phantom type device, and this is the device that is such a purchase. The device feeds a condenser studio microphone, which works much like a condenser itself. Only instead of a movable capacitor plate, a microphone membrane functions. The intensity of operation and the amplitude of the displacement determines the strength of the sound that the microphone in this moment processes. The operating voltage changes accordingly, and we get the desired effect of improving the operation of the sound recording device.

    It should be noted that the scheme is quite original, but it works. In any case, the cost of phantom power is not prohibitive, if its capabilities are not satisfied, the financial costs will not be critical.

    Whatever it was, a new 48 V power supply must be connected somewhere and somehow, and also be fastened for safety. Moreover, without it, condenser microphones simply will not function. Why 48 V? Because this figure is supported by most microphone manufacturers and sound cards, this is already a definite tradition. In fact, a condenser microphone is capable of operating over a wide voltage range.

    The device itself, that is, phantom power, should be fixed in a convenient place so that it does not interfere, and at the same time be easily accessible. All necessary cables are connected to the fixed device, including the cable for connecting the microphone. A dedicated button allows you to turn phantom power on and off as needed.

    Phantom power is an inexpensive and effective way to improve the performance of your computer's recording system as much as possible. The device is popular with consumers as it is safe to operate. Unless in the event of a short circuit in the cable, especially in the absence of the proper grounding for such cases, the capsule may be damaged, which is easy to replace.

    According to the majority of users, it is worth ordering the device from Chinese retailers. Especially if there is a need to work with high quality sound without buying expensive professional equipment.