Do Microphones Plug Into Amps? (Guitar Amps, Preamps, Power Amps, Etc)

When dealing with any kind of audio signal, amplification is often a necessary step between devices (microphones to mixers, mixers to loudspeakers, etc.). Amplifiers, as the name suggests, are needed to provide such amplification to the audio signals.

Do microphones plug into amps? Microphones output mic levels signals which require amplification to become line level for use with other audio equipment. Therefore, mics plug into mic preamps. Mics can also plug directly into any other amp with an audio input, though not all amps expect or work well with mic level signals.

In this article, we'll discuss some common audio amplifiers and whether microphones work well with them or not.

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Microphones Typically Plug Into Microphone Preamplifiers

Microphones output mic level signals. These mic level signals require amplification to become line level signals (for use in mixing boards, digital audio workstations, and audio recorders).

Microphone preamplifiers provide this gain. Therefore, microphones typically plug into microphone preamplifiers!

Microphone preamps come in all shapes and sizes.

• Some a single-channel while others are multi-channel.
• Some are standalone while others are built into mixing board channel strips and include equalization and compression.
• Some provide options for phantom power, high-pass filtering, passive attenuation devices, and/or phase flip, while others do not.

Here are a few examples of microphone preamplifiers:

The ART TubeOpto 8 is an 8-channel microphone preamp with tube amplification electronics:

The Cloud CL-1 is a single-channel microphone preamp designed for use with low-sensitivity dynamic microphones and acts as an amplifier before the microphone preamp.

Microphone preamps are also available in most audio interfaces. Audio interfaces provide mic inputs/preamps and allow us to connect our microphones to computers with analog-to-digital converts.

One such audio interface with microphone preamps is the popular Focusrite Scarlett 2i2:

Note that further amplification is required if a microphone is plugged directly into a powered loudspeaker. We'll discuss this in more detail later.

To simplify these levels with values, I've provided the following table:

	Lower-End Signal Strength	Upper-End Signal Strength
Mic Level	-60 dBV (1 millivolt)	-20 dBV (100 millivolt)
Line Level	-10 dBV (316 millivolts) Nominal (Consumer)	+4 dBu = 1.78 dBV (1.23 millivolts) Nominal (Professional)

Speaker level has much more voltage than line level but is highly dependent on the impedance and size of the loudspeaker it is driving.

Microphone preamps will provide enough gain to get the mic level signal to line level. Once at line level, this signal can easily be used in professional audio equipment.

Without a preamplifier, the output signal of a microphone wouldn't properly mix with the other audio sources in the mixer/recorder.

We could technically plug a microphone into a line level input. The line level input would provide gain, but it would also introduce a lot of noise, degrading the microphone signal. This is because the line level input is not expecting such a low signal level.

How do we plug a microphone into a mic preamplifier?

XLR connections are typical when plugging a microphone into a preamplifier. Usually, the microphone connects to an XLR cable, which then carries the signal to the microphone preamplifier.

XLR cables carry balanced audio from the microphone to the preamp. This allows for less signal degradation and electromagnetic interference. Microphone preamplifiers are generally designed to expect balanced audio and are built with differential amplifiers to ensure the balanced audio signal is properly received.

To read more about microphone connections, check out my article What Do Microphones Plug Into? (Full List Of Mic Connections).

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Can Microphones Plug Into Power Amps?

It is possible to physically/electrically connect a microphone directly to an audio power amplifier via the amp's XLR inputs (or via an adapter if the power amp does not have XLR inputs).

However, power amps are typically built with line level inputs. In other words, they “expect” line level signals, which are much stronger than the mic level signals a microphone outputs.

Therefore, connect a microphone directly to a power amp would work. Still, the signal-to-noise ratio would be terrible because the gain would not be appropriate for the mic level signal.

So in order to connect a microphone to a power amp, it's important to have a microphone preamplifier in between the mic and power amp. This preamp could be a standalone unit, or it could be built into an audio mixing board.

A mixing board or standalone preamp may also supply phantom power if your microphone requires it!

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Can Microphones Plug Into Powered Speaker Amps?

Many powered loudspeakers have built-in mic inputs and are capable of boosting a mic level signal to speaker level. So yes, a microphone can often be plugged directly into a powered speaker amp and work just fine.

To properly plug a microphone into a powered speaker, plug the microphone into the mic input of the speaker.

Note that passive loudspeakers will not be able to boost the mic level signal. Although signal can be transferred by plugging a microphone directly into a passive speaker, the mic level signal will only barely be able to move the speaker to produce sound.

For more info on plugging microphones into speakers, check out the following My New Microphone articles:
• How To Plug A Microphone Into A Speaker
• Do Microphones Need Loudspeakers Or Headphones To Work?

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Can Microphones Plug Into Guitar/Bass Amps?

Yes, however, adapters are most often required.

Guitar and bass amps have 1/4″ TS jacks, while microphones typically have XLR outputs. Therefore, to plug a microphone into a guitar/bass amp, we need some sort of XLRF to 1/4″ TS (or TRS) adapter.

For more info on plugging microphones into guitar and bass amps, check out my article How To Plug A Microphone Into A Guitar Or Bass Amp.

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Related Questions

Why put a microphone in front of an amp? In recording situations, putting a mic in front of a guitar or bass amplifier will record a strong, isolated audio signal from the amp. In live situations, placing a mic in front of an amp will help reinforce the sound of the amp by allowing its sound to be projected by the PA system and not just the amp speaker.

To read about my recommended microphones for miking amps, click through the following links.
• Best Microphones For Bass Guitar Cabinets
• Best Microphones For Electric Guitar Cabinets (Live)
• Best Microphones For Electric Guitar Cabinets (Studio)

Can you plug a microphone into a line input? Though it's physically quite easy to plug a mic into a line input, it's not recommended. A line input expects a line level signal, which is much stronger than a mic level signal (from a microphone). Pluggin a mic into a line input results in a low-level signal with a terrible signal-to-noise ratio.