We have covered issues related to microphones before, such as the different types of design or the fundamental differences between dynamics and capacitors, as these are usually the fundamental criteria to consider before choosing the model that is best for you depending on the model. to the goal you want to give it. When we go into the microphone impedance, we are, to put it mildly, spinning correctly, because as we will see below, while not too influential a factor, it can make a lot of difference in the end result. We will get into the question, and how can it be otherwise, we have to do it from the start.
What is impedance in a microphone
The literal definition of impedance tells us that it is “a measure of the opposition / resistance to alternating current in a circuit when voltage is applied to it”. Impedance is measured in ohms, just like resistance, and in fact, this term is often referred to as the “AC resistance” of a circuit.
However, when we shift the impedance towards the audio niche and more precisely that of the microphones, we can say that it is applied in a somewhat different way:
- The audio signals are AC voltages (alternating current) because they have negative and positive voltages (the positive and negative amplitude of the signal). Audio signals are therefore alternating currents which have a positive part and a negative part.
- The impedance of a microphone controls the flow of alternating current in an audio circuit when a voltage is applied to the signal.
- All microphones, like any electronic device generating an alternating voltage, have a output impedance.
- A microphone creates a circuit with the preamp (or other audio circuit) to which it is connected. This device has an input impedance called microphone load impedance.
- The microphone output impedance must be a fraction of the preamp input impedance for the circuit to work.
In short, impedance is the resistance of the alternating current. The higher the impedance of a microphone, the more prone the cable is to interference and loss of signal. Additionally, depending on the preamp input, a few more decibels in volume may be lost in the mixer, and if the mic impedance is as high as the preamp input, up to 6dB is. lost in the most extreme case.
The most common microphones today are all low impedance, with values between 50 and 600 ohms. Los previos de micrófono tienen en su mayoría impedancias de entrada de unos 2000 ohmios, así que teniendo en cuenta todo esto, la impedancia del micro siempre será menor que la del preamplificador, por lo que las perdidas en la señal son, en teoría, mínimas in any case.
What should you keep in mind regarding impedance?
In the data sheet of any microphone you will find its impedance value. Any professional mic is considered “low impedance,” meaning its range is around 50-600 ohms, although it’s true that you will rarely see a professional mic with more than 250 ohms. The general impedance ranges are as follows:
- Low impedance microphones: <600 Ω
- Medium impedance microphones: 600 Ω – 10,000 Ω
- High impedance microphones:> 10,000 Ω
As we mentioned earlier, when choosing a microphone you should first be clear whether you are going to be using a preamplifier, or if not, if you intend to use it on a PC without prior input, what is the impedance of the microphone input of your card. his. Unfortunately, most motherboard manufacturers don’t specify these parameters, but if they tell you which chip they mount, you can search the internet for it, and even if you can’t find the specific parameter, you can find tables of compatibility.
For example, on an MSI Z370 Gaming M5 motherboard, it doesn’t say what the impedance is but it uses a Realtek ALC1220 chip, and looking for information about it shows that it has impedance detection. and that it is compatible with microphones up to 600 ohms. impedance, which means that the preamp on this chip is most likely 600 ohms.
Finally, the lower the microphone impedance, the better because it will have a lower resistance and therefore will be less subject to interference and signal loss due to the cable.
With digital microphones things are a little different, and it is not uncommon for you to see in specifications for headset microphones with USB connection impedance values of over 2000 ohms (for example, the microphone of some SteelSeries Arctis Pro Wireless or Corsair Virtuosos have 2200 ohms), values that could make us think the mic is “bad”.
However, when we are dealing with a digital product (remember it is USB powered) things are a bit different, and these devices frequently incorporate their own preamplifier with a much higher impedance margin, so despite such impedance, they don’t. will experience interference or loss, especially because these types of impedances often occur in wireless devices. However, if you see these impedance values in an analog microphone, you need to be careful about which preamplifier you are going to use and the rest of the settings we have explained in this article.