In the two previous installments we have talked about the different elements or capsules of the microphones, where we detail the condenser and the dynamic, these being the two most important and common in the industry, but not the only ones.
Juan Tamayo *
Possibly in another installment we will talk about ribbon or ribbon microphones. We also talk about the polar pattern and the different properties it has, including the distance factor and the relationship with the gain. For this issue we will talk about more diverse topics.
The phantom power or phantom power is one of the issues that are least addressed in the study in audio subjects, and unfortunately you do not have all the benefit that we can squeeze that voltage that gives us the console. Some only refer to this as the + 48V that gives us a processor or a console.
The phantom source is developed to polarize the capacitor-type capsules. Due to its electrical nature, a capacitor requires a voltage differential in order to operate. Additionally, over time this voltage is used to power a pre amplifier in the microphones and make the voltage path through the cable from the microphone to the console more stable. Some elements will only require + 9, + 24 or + 48V (if it is fed with higher voltage it may not have problems, if it is fed with a lower voltage it may not work or the floor noise increases).
But those are not the only applications. Nowadays, the phantom power is also used to power live direct boxes, power remote mixers, power up circuits of light emitting diodes or LEDs, among many other applications.
The phantom source has also been considered as the father of the Power Over Ethernet or PoE, because its application is very similar and can be said to have the same functional nature. But, dear reader, keep in mind that if you are not careful with this voltage it can affect or damage some electronic elements.
This development is designed to travel through the positive channel and the negative channel of the balanced signal. If you connect an unbalanced item that does not have a phantom source discharge circuit such as a computer or a mixer, it can seriously damage the output circuit of the audio device connected to the signal fed with the phantom source.
In the previous installment we talked about the listening angles of a microphone, the frequency response has to do a bit with this. We can define the frequency response term as the ability to hear a microphone in the whole spectrum of sound frequencies.
It is generally defined by a graph that goes from 20 Hz to 20 KHz, like the human ear, but in some microphones it is taken from 0 to 25KHz or up to 30 KHz, this is because in many cases the signal when it reaches 20 KHz has already lost 10 dB, then microphones are developed so that when they reach 20 KHz their loss is not considerable. The engineer or interested person is offered to observe the answer to beyond where he can listen to study its stability.
I think these graphics are cold because they often do not express how a microphone causes the captured signal to change. Many consider that the microphones that have a flat frequency response are the best (they do not change the input signal). I differ from this theory, I think a good designer should look for the microphone that best suits the application you want to design.
A clear example is that if a microphone is required for a teleconference, I should look for a microphone whose frequency response enhances the frequencies of the human voice (means) and, for example, that attenuates the low frequencies, which is where the frequencies are. produced by mechanical elements such as air conditioning units.
In this issue we talk about the phantom source and the frequency response of the microphones. If you have any questions please do so through the digital version of the magazine or you can write me at firstname.lastname@example.org.
* Juan Tamayo is a senior applications engineer for Audio-Technica Latin America, with more than 10 years of experience making audiovisual projects as a designer, integrator, consultant, among other functions.