When it comes to inputs, particularly those that are needed to operate equipment like microphones.
It is always important to have enough information so you can make your equipment usable with your inputs.
This post will address microphones and Auxiliary or Aux inputs because this is a common topic among new audio engineers and technicians.
It is possible to put a microphone in an aux input. Dynamic mics can be easily connected using the appropriate connector. With a condenser mic it can be a bit challenging as you’ll need a mono-to-stereo adapter and a preamplifier to boost the low level signals to line level signals. Auxiliary inputs by design, work with amplified signals.
In addition to this; a proper setup and input level adjustment are also crucial to prevent feedback, signal loss and noise issues.
Therefore your microphone needs a pre-amplifier to ensure that it work optimally because typically microphones don’t put out enough voltage.
If you do plug in your microphone into an Aux input with out a pre-amplifier you’ll most likely have a lot of noise in the signal or you’ll simply have a weak signal.
However, many computers especially those with built-in “Realtek High Definition Audio, usually have dual purpose input jacks and drivers like “Realtek HD Audio Manager that asks you whether you’re plugging in a microphone or a line-level device… if you have that or something similar you’re good to go with almost any microphone that has a 3.5mm AUX style plug.
AUX inputs
An auxiliary input, commonly known as an “AUX input” or “AUX port,” is a type of audio input found in many electronic devices, particularly in audio equipment and car stereos.
The auxiliary input is especially designed for amplified signals; for this reason, connecting a microphone into an aux input is simply matter of using the appropriate connector and a preamplifier (for condenser mics).
Aux inputs allow you to connect external audio sources, such as smartphones, tablets, MP3 players, or other audio devices, directly to the main device for playback.
Purpose of an AUX Input
The primary purpose of an aux input is to enable users to expand the audio capabilities of their host device by connecting external audio sources.
It allows you to play audio from devices that do not have built-in speakers or audio output capabilities through the host device’s audio system.
This feature is especially useful in situations where you want to listen to content from devices like smartphones, MP3 players, tablets, laptops, or other audio players using the speakers or audio equipment connected to the host device.
Audio Levels
It’s important to understand the different types of audio levels to understand equipment and inputs.
Therefore this part of the post will discuss the main types of audio levels that one will obviously encounter when dealing with equipment connections.
Microphone Level
A microphone basically captures sound by simply converting pressure changes in the air into electrical currents in a wire.
The electrical currents created by these pressure changes are very subtle that’s why microphones are said to have a weak signal.
It is for this reasons that we utilize a microphone pre-amplifier – to amplify and boost the signal to a more stronger and usable level.
A microphone pre-amp is how you convert a mic level signal into line level signal.
All a pre-amplifier does is, it takes in a microphone level signal, amplifies it, and outputs a line level signal. This is controlled by the gain knob on your mixing console, audio interface, or outboard mic pre-amp.
Instrument Level
In order to have a basic understanding of Instrument level signals, let’s take the basic example of guitars.
Simply, the pickups of an electric guitar convert the vibrations of the strings into electrical currents.
Similar to those signals from a microphone, the electrical currents from a guitar pickup are very weak which basically makes the audio signal weak.
In this case a pre-amp can also be used to boost or strengthen instrument level signals to line level.
Line Level
Line level is an audio level that is optimized for use with professional audio equipment, such as mixing consoles, outboard effects, and amplifiers.
Speaker Level
The fact is that Line level is adequate for sending signals between devices, but it is not strong enough to power a speaker.
In order to power a speaker, you need an amplified line level signal.
In order to amplify your line level signal, you can use a power amplifier.
A power amplifier simply takes in a line level signal, amplifies and boosts it, and outputs a speaker level signal that is strong enough to power a speaker.
Now that we’ve discussed the various audio levels that you need to know in order to understand equipment better let’s get into the two most important connection types namely the Balanced Connection and Unbalanced connections.
Balanced
A balanced connection is sometimes called a symmetrical connection and it prevents unwanted noise and hum.
Balanced connections are usually the connection of choice for most when large distances need to be bridged, especially when carrying weak signals like those of microphones.
For a balanced connection, both linked devices need to have a balanced socket to ensure that the emitted signal is duplicated: one of those signals is sent normally and the other copy is sent with reversed polarity.
The device at the other is responsible for receiving both the signals separately, then re-reverses the polarity of the copied signal, then combines the two signals.
The point of this “switching-trick” is that the original signal becomes becomes boosted so its louder and that any noise that is picked up while travelling along the two wires in the cable disappears.
Unbalanced
An unbalanced cable consists of two connectors with two conductors each and they are connected by two wires within the cable— comprising of a signal wire and a ground wire.
In most cases it is easy to identify a cable designed to carry an unbalanced signal by its connectors: because each wire has to terminate at the connector with its own unique contact point, an unbalanced cable requires only two conductors at the connector.
A standard TS (or “tip-sleeve”) guitar cable is the unbalanced cable you’ll run into in most stage work.
Standard RCA cables used for many AV components are also unbalanced cables.
How to connect your microphone into an Aux Input
Dynamic Microphones:
Dynamic microphones due to their design are ideal for live performances and recording in less controlled environments.
They don’t require external power and generate a signal through electromagnetic induction when sound waves hit their diaphragm.
Typically, dynamic microphones have low output impedance and are compatible with most audio devices, including aux inputs.
To connect a dynamic microphone to an aux input, you’ll need a cable with the appropriate connectors: XLR (microphone end) to 3.5mm stereo jack (aux input end). Make sure the cable is mono, as dynamic mics usually output mono signals.
Condenser Microphones:
Condenser microphones are more sensitive and offer higher fidelity, making them popular for studio recordings, podcasts, and other critical audio tasks.
They require external power, often referred to as “phantom power”.
It is usually provided by the audio interface or mixer they connect to.
Condenser microphones have higher output impedance than dynamic mics, which can be problematic when connecting to an aux input that is designed for lower impedance devices.
To connect a condenser microphone to an aux input, you’ll need an XLR (microphone end) to 3.5mm stereo jack (aux input end) cable along with an impedance-matching adapter or preamp.
The preamp will ensure that the higher impedance of the condenser mic is correctly matched to the lower impedance of the aux input, preventing signal loss, feedback and distortion.
Avoid using passive adapters as they may not provide proper impedance matching and could result in degraded audio quality.
Set the input level on the aux input to an appropriate level to avoid clipping or distortion. Start with a lower level and gradually increase it until you achieve a clear and distortion-free sound.
If using a mixer or audio interface, adjust the input gain accordingly to avoid overloading the signal.
After connecting the microphone, listen for any feedback or noise issues. Adjust the positioning of the microphone and the gain level to minimize feedback and unwanted noise.
Challenges of using condenser mic
Challenges with using condenser microphones with aux inputs primarily stem from their higher impedance and requirement for phantom power.
These challenges can affect the compatibility and functionality of condenser microphones when connected directly to an aux input.
Here’s a detailed explanation of these challenges:
Higher Impedance
Condenser microphones typically have higher output impedance compared to dynamic microphones.
Most aux inputs are designed to accept line-level signals with lower impedance, not the higher impedance signals from condenser mics.
Connecting a condenser microphone directly to an aux input can result in a weak and distorted audio signal due to impedance mismatch.
Phantom Power Requirement
Condenser microphones require an external power source to operate, known as “phantom power.”
Phantom power is typically supplied through a dedicated XLR input on audio interfaces, mixers, or preamps, rather than through aux inputs.
Since aux inputs are not designed to provide phantom power, condenser microphones won’t function correctly when connected directly to them.
Additional Equipment
To use a condenser microphone with an aux input, additional equipment is necessary to address the impedance and power requirements:
1. Preamp: A preamplifier is needed to boost the microphone’s low-level signal to line-level, making it compatible with the aux input.
2. Impedance-Matching Adapter: An impedance-matching adapter ensures that the microphone’s higher impedance matches the lower impedance expected by the aux input.
Quality and Noise Issues
Improperly matched impedance can lead to signal loss, reduced audio quality, and increased noise levels.
Inadequate preamps may introduce unwanted noise and affect the overall sound quality of the microphone.
Alternatives for connecting microphones
1. Dedicated Audio Interfaces
Dedicated audio interfaces are excellent alternatives for connecting microphones. They offer specialized inputs designed specifically for microphones, including XLR or TRS jacks with built-in preamps and phantom power support.
Audio interfaces are particularly beneficial for computer-based setups, as they allow you to connect your microphone directly to your computer via USB or other digital connections.
2. USB Microphones
USB microphones are convenient options for users who want a simple setup without the need for additional audio interfaces or mixers.
These microphones have a built-in analog-to-digital converter and connect directly to a computer or other devices with a USB port. They are easy to set up and typically do not require phantom power or additional adapters.
3. Wireless Microphones
Wireless microphones offer greater mobility and freedom of movement, making them ideal for live performances, presentations, and other situations where a wired connection may be impractical. They consist of a wireless transmitter connected to the microphone and a receiver that connects to the audio system or mixer.
4. Bluetooth Microphones
Bluetooth microphones provide a wireless connection option for compatible devices with Bluetooth capabilities.
They can be connected directly to smartphones, tablets, or Bluetooth-enabled audio systems without the need for physical cables.
