Microphones are complex devices to understand and the terminologies around them do not make it easier. “Microphone Gain”, a term often thrown around, is critical in understanding these devices. Frankly, I did not know much about it either. So, I decided to do a bit of research to understand what it really means and how it affects the user experience. And I will share all of it in this article on “What is microphone gain?”.
Simply put, gain describes the capability of a mic to increase the amplitude of a sound signal. The gain amplifies the signal from mic to line level so the signal becomes compatible with audio equipment. Preamp is the first part of the circuit and it controls the gain of the microphone. I know it is a bit confusing but reading it further will help you get a clear understanding of Microphone gain.
Understanding The Different Terminologies
To understand the mic again, we will have to revisit the basics. You would need to know how the sound travels in a circuit and what are the factors that influence it.
Sound is a form of mechanical energy which the microphones convert into electrical signals. The signal travels in the circuit and as it reaches the end it gets converted into mechanical energy. Sound signals are measured in dBu or dBV – measurements that are relative to voltage.
0 dBu is equal to 0.775 V while 0 dBV is equal to the 1 volt.
Decibels are a logarithmic ratio and as it reaches +6 dB it doubles the voltages. But as it comes down to -6 dB, it cuts the voltages in half. We would be using only dBu from here on for the sake of better understanding.
Another point worth discussing is, microphones are generally analog but, in some instances, they can output digital signals as well. Usually, only analog signals need amplification. Amplifying digital signals would cause multiplication which would produce distortion in the resolution.
So, What Is Mic Level & Line Level?
Signal coming from the microphone is known as “mic level” and it is specified between -40 dBu and -60 dBu. The problem is this signal is not compatible with the professional equipment or what is known as line level.
Most professional equipment only works with a signal that is about +4 dBu. The equipment includes an audio workstation and mixing consoles.
One must be mindful that both mic and line levels are in fact average values. These values differ from mic to mic and the loudness, sensitivity and gain applied to the sound also have influences on it.
Sound engineers believe that the line level is about 100 to 1,000 folds stronger than microphone level. And it is why gain is needed to boost the signal to the level where it can become compatible with professional equipment.
Why Microphones Cannot Deliver Output Level?
It is a fair ask and frankly it is quite possible as well. Companies are only hesitant to implement it because of the history and marketing. To make it possible, the entire design of the microphone would have to undergo some changes. It would make the microphones too bulky and heavy to hold which is simply not an option.
How Does Gain Affect The Performance of Microphone?
To bring the mic level to the line level microphones come with a preamp which is present at the start of circuit. These preamps should have enough gain to boost that signal to make it compatible with the line. If we connect the output of the microphone directly to the line it would deliver a very poor signal-to-noise ratio.
The “gain” is the ability of the microphone to boost the mic signal. It makes the signal more powerful. The energy comes from either phantom power, batteries, or AC wall plug.
Usually, the audio signal goes through stages in order to become strengthened enough for the line. It can either be amplified via built-in preamps or by external sources like interfaces and mixing consoles. With the external amplifier gain is applied before the signal goes through the mic. While with the built-in, it is applied afterwards.
The difference between the signal at mic level and the line level determines the microphone gain. The more the gain, the better. You would get a better result for a microphone that has higher gain as it will deliver clear audios. Those that have low gain will produce self-noise – distorting the quality of audio.
Gain From Built-In Amplifiers
Condenser Microphones and some other mics come with built-in amplifiers in their design. It is because the signal produced by the mic itself is too weak in voltages and has high impedance- rendering it useless. Impedance is the resistance encountered by the signal when it travels in the circuit.
To strengthen the signal, amplifiers are installed right after the capsule. Consequently, it improves the signal and reduces the impedance which enables it to run through long cables without distorting.
Gain provided by such amplifiers is often fixed although some come with attenuation pad switches. These switches give you control over the degree of amplification. You can either decrease or increase as per the situation.
With that said, there are not many microphones that do it effectively. Some are not well-designed and thus cannot effectively strengthen the signal to the line level. It is why you often experience self-noise on the cheaper microphones. To get your hands at the best of microphones read more at microphonesgeek.com
Gain From External Amplifier
As discussed earlier, external amplifiers can also be used to strengthen the audio signal. And since these are pretty powerful and packed devices, they deliver much stronger signals. These devices apply the gain at mic input.
There are few things that you would have to be mindful about while using these devices. Several amplifiers have multiple input channels. You need not to plug the microphone in the line input. It requires a stronger signal which the mics are unable to provide and results in poor overall gain.
Unlike built-in preamps, external amplifiers almost always deliver the signal that is compatible with the line. You must also know that the conversion of digital to analog is also necessary which requires a proper ADC.
Most of the mixing consoles have built-in preamps but usually standalone amplifiers are the best choice. While using standalone to the mixer you need to ensure that you are not sending the signal to the mic input but to the line input.
You can connect the standalone preamps with digital audio workstations via digital to analog converter. Some workstations use interfaces as well to provide microphone input. Most of the audio interfaces come with pre-installed preamplifiers.
Factors That Influence Microphone Gain
There are few factors that influence the microphone gain. Sensitivity and the proximity to the sound source are the most important of them.
Microphones that have built-in preamps are relatively more sensitive than passive mics. It is why condenser mic requires less gain to reach line level. And it is the reason why these microphones are efficient at picking up low frequencies.
Secondly, a microphone placed near to the sound source requires less gain than the one placed far away.
Too much amplification can also result in distortion. Your goal is to achieve nominal line level not more. While over driving the signal you would see a red light on the amplifier which should be taken as a warning sign.
Mic Gain Vs Volume – Are These Same?
Some people use these both terms interchangeably but they are actually quite different. Gain is actually strengthening of signal to bring it at the line levels. While the volume is the intensity of sound coming from each source. You would see separate knobs for both at your amplifier. Increasing the gain may also increase the volume but increasing volume would not affect the gain.
Confusion between the terms is probably because they have the same units which are dBs. You should use gain to adjust the instruments and make their signal compatible with equipment. While the volume should be used to strike a balance between different instruments that are available.
Conclusion- What Is Gain In Microphone
Well, this is all that you need to know about microphone gain as a beginner. We know it is quite a difficult subject to understand but you will get a hold of time with time. As of now all you need to know is that gain is the capability of the microphone to make the signal compatible with the line.
There are a lot of factors that influence it and we have discussed some of them in our discussion. We hope this article has cleared your confusion around the subject. If you have any query let us know in the given section. We would love to respond.