Some situations may call for plugging your mic(s) into a guitar or bass guitar amplifier. You could be in a jam space without a PA system or be looking to add crunchy distortion (and other effects) to your vocals.
How do we plug a microphone into a guitar or bass amp? To plug a mic into a guitar/bass amp, we need to adapt the mic cable to a TS (tip-sleeve) connector and insert the TS into the amp input. Note that TRS would also work but is not the ideal connection. If using an active mic, ensure a power source is put in-line between the mic and amp.
In this article, we'll go over the cable adapters/wiring required to connect a mic to a guitar or bass amp. We'll also discuss the issues once a microphone is connected to a guitar or bass amp.
Adapting An XLR Microphone Cable To 1/4″ TS
Microphones typically have balanced XLR outputs, while guitar amps almost always have unbalanced 1/4″ Tip-Sleeve inputs.
Therefore, to connect a microphone to a guitar amplifier, we must have an adapter cable to connect the microphone to the guitar amp.
This adapter requires a female XLR at one end and a 1/4″ TS (or, alternatively, a TRS) at the other end. There are two main adapter styles for this:
- XLRF to TS cable: this is a cable of any length that has an XLRF at one end and 1/4″ TS plug at the other.
- XLRF to TS adapter: this is a simple adapter that can connect to the end of a regular XLR cable (at the XLRM end) and adapts the XLR connector to a 1/4″ TS plug.
With either of these adapters, we can easily connect a microphone to a guitar or bass amplifier.
For more info on the XLR connector, check out my article Why Do Microphones Use XLR Cables?
It's important to note here that an XLRF – 1/4″ Tip-Ring-Sleeve would also probably work, even though the amplifier plug is designed for Tip-Sleeve.
This is because microphones send mono balanced audio. So long as the Tips and Sleeves of the connections connect, there shouldn't be any issues. The Ring of the TRS plug would be nullified in the amplifier's TS jack.
Providing Power For Active Microphones
Connecting a microphone to a guitar amp is one thing. Having a signal transfer from the mic to the amp is another.
With passive microphones (moving-coil dynamics and most ribbon dynamics), the signal is transferred without any need for external power.
Active microphones (all condensers and some ribbon mics), on the other hand, do require external power. This power is typically provided by DC bias voltage, phantom power, or an external power supply, none of which a guitar amplifier provides.
So how do we power active microphones that are connected to a guitar amplifier? We must provide the necessary power by other means.
Note that tube microphones typically have external power sources and can easily connect to and send signals to guitar amps as long as they're powered.
As for phantom-powered or DC-biased microphones, we must find alternative ways to supply the power needed. External power sources are simple ways to apply the necessary voltage to these microphones.
For phantom-powered microphones, check out the Neewer 1-Channel Phantom Power Supply (link to check the price on Amazon).
As for DC-biased microphones, most of them are lavalier mics that connect to, and get power from, wireless transmitters.
To connect a wireless microphone to a guitar amp, set up the wireless system and then adapt the wireless receiver's output to connect to the guitar amplifier.
For more information on wireless microphones, check out my article How Do Wireless Microphones Work?
For more info on properly powering microphones, check out the following My New Microphone articles:
• Do Microphones Need Power To Function Properly?
• Do Microphones Need Phantom Power To Work Properly?
Mic Signals In Guitar And Bass Amps
Guitar and bass amps usually receive electric guitar or bass audio signals. Microphones also output audio signals, though there are some notable differences, including:
Frequency Response Is Limited In An Amp
Guitar and bass amplifiers/cabinets do not produce sound across the entire audible sound spectrum of 20 Hz – 20,000 Hz.
In general, they only produce up to about 6 kHz. Bass cabinets are capable of producing lower sounds (below 40 Hz), while guitar amps typically have a higher low-end cut-off.
A typical microphone will have a much wider frequency response than that. Therefore, a guitar/bass amplifier will not reproduce a mic signal in the truest way.
For more info on frequency response, check out my article Complete Guide To Microphone Frequency Response (With Mic Examples).
Balanced Mic Output – Unbalanced Amp Input
XLR microphones output balanced audio while guitar/bass amplifiers have unbalanced (TS) inputs. The adapters mentioned above will take care of changing the audio from balanced to unbalanced.
As discussed previously, it's generally fine to plug a balanced TRS plug into an unbalanced TS jack, so it's not a big deal if the adapter is an XLRF to 1/4″ TRS.
That being said, I would not advise adapting the mic signal to an unbalanced cable that connects it to the amplifier. Long unbalanced cables are susceptible to electromagnetic interference and may cause unnecessary signal degradation.
For more information on balanced and unbalanced signals, check out my article Do Microphones Output Balanced Or Unbalanced Audio?
Extra Gain (Amp Expects Instrument Level, Not Mic Level)
Another distinction to make between the typical microphone output and the expected amplifier input is the signal level.
Mic signals are generally weaker than instrument level (guitar and bass pickups, etc.) signals. Therefore, more gain would be required from the amp to bring the signal to the same volume.
For more info on microphone gain, check out my article What Is Microphone Gain And How Does It Affect Mic Signals?
For more info on mic and instrument levels, check out my article Do Microphones Output Mic, Line, Or Instrument Level Signals?
Connecting A Microphone To Guitar Effects Pedals And Pedalboards
Guitars and basses often run through effects pedals before connecting to their respective amplifiers. Microphones can also connect to pedals and pedal boards before connecting to an amp.
Guitar and bass pedals typically have 1/4″ Tip-Sleeve jacks, just like guitar/bass amplifiers.
To plug a regular XLR microphone into a guitar pedal, follow the instructions above for connecting a mic to an amp. All that is needed is an XLRF – 1/4″ TS adapter!
A Note On Feedback
Like any loudspeaker, a guitar/bass amplifier/cabinet will be prone to microphone feedback (when a microphone is connected).
To avoid feedback, keep the amp gain below the gain-before-feedback threshold while trying to distance the mic from the cabinet and point the mic away from the cabinet.
For a deeper read into microphone feedback, check out my article 12 Methods To Prevent & Eliminate Microphone/Audio Feedback.
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)
What do you plug a microphone into? Although microphones can plug into any type of audio input (given the proper adapter cables), they typically plug into mic inputs with mic preamplifiers. These inputs/preamps provide the necessary gain to bring the mic level signal to line level for use with other audio equipment.
For a detailed account of microphone connections and connectors, check out my article What Do Microphones Plug Into? (Full List Of Mic Connections).
Choosing the right microphone(s) for your applications and budget can be a challenging task. For this reason, I've created My New Microphone's Comprehensive Microphone Buyer's Guide. Check it out for help in determining your next microphone purchase.