To learn how to connect instruments to a PA system, match each instrument to the right kind of input: high-impedance instruments (electric guitar, bass, passive keys) need a DI box into an XLR mic input, while line-level gear (synths, mixers, drum machines) can go straight into a line input. Mics and acoustic-electric instruments each have their own path too. Get the input type and gain right and everything else falls into place.
This is the live counterpart to capturing a clean signal in the studio, where the same impedance and gain rules apply when you stage your gain correctly.
Know your three input types first
Every PA channel expects one of three signal types, and sending the wrong one causes weak, distorted or noisy sound:
- Mic level — the tiny signal from a microphone. Uses an XLR input and needs lots of preamp gain.
- Line level — a strong signal from synths, audio interfaces, laptops and other mixers. Uses TRS or RCA inputs and needs very little gain.
- Instrument (Hi-Z) level — the high-impedance signal from an electric guitar or bass pickup. Needs a DI box to convert it to mic level before it hits the PA.
If you are fuzzy on the cable side of this, our explainer on XLR vs TRS cables for live sound shows which connector does what.
The reason this matters comes down to two things: signal strength and impedance. A line input expects a signal that is already strong, so it applies almost no amplification. A mic input expects something tiny and applies a great deal. Feed a strong line signal into a mic input and it overloads and distorts even with the gain right down; feed a weak instrument signal into a line input and it sounds thin and lifeless because there is no preamp behind it to lift it. Impedance is the second half of the story: a passive guitar pickup is a high-impedance source, and plugging it into a low-impedance input drains the high frequencies and dulls the tone. A DI box fixes both problems at once, presenting the pickup with the high impedance it wants and outputting a balanced, mic-level signal the PA is happy with.
Connecting each instrument
Electric guitar and bass
Run the instrument (or the amp’s line/DI out, or a pedalboard output) into a DI box, then an XLR cable from the DI to a mic input on the PA or mixer. If you want amp tone, mic the cabinet instead with a dynamic mic.
Keyboards, synths and drum machines
These usually output line level. Use a stereo pair of TRS or two mono cables into two line inputs, or a stereo DI if the run is long. Pan them hard left and right for a wide stereo image.
Acoustic-electric guitar
The onboard pickup is high-impedance, so route it through a DI box into a mic input, just like an electric.
Microphones and vocals
Plug the mic straight into an XLR input. Condenser mics need phantom power switched on; dynamic mics do not. For singers, our guide to micing a singer live covers placement.
Active and passive DI boxes
You will meet two flavours of DI box and it is worth knowing which to reach for. A passive DI uses a transformer and needs no power, which makes it rugged and quiet; it suits hot, strong sources such as the line out of a keyboard or an active bass with onboard preamp. An active DI contains its own buffer circuit powered by phantom power or a battery, giving it more gain and a higher input impedance. That makes it the better choice for weak, truly passive sources like a passive bass or a piezo acoustic pickup, where it preserves more low end and sparkle. When in doubt for a passive instrument, an active DI is the safer bet; for anything already at line level, a passive DI is plenty.
Set the gain before you set the level
Once connected, bring up each channel’s gain (trim) with the fader down. Play or sing at performance volume and raise the gain until the channel meter peaks healthily without clipping. Only then bring the fader up into the mix. Setting gain channel by channel is the foundation of a clean live mix — see how to gain stage a live mixer.
Keep signal paths tidy
If your stage is more than a few metres from the mixer, a snake cable keeps your runs neat and your channels organised. Label your inputs and you will never lose track of what is plugged in where.
Common mistakes to avoid
A handful of errors account for most of the “it does not sound right” moments at soundcheck. Run through these before you start blaming the gear:
- Phantom power on the wrong channel. Switching on the 48V for a condenser mic is fine, but sending phantom power down an unbalanced line connection or into vintage ribbon mics can cause problems. Engage it only where it is needed.
- Stereo gear summed to mono. Plugging only the left output of a stereo keyboard into one channel loses half the sound — many synths only send a full signal when both outputs are connected, or have a mono switch. Use both outputs or set the keyboard to mono.
- Ground hum from a guitar rig. Connecting an amp and a DI to the same instrument can create a ground loop and a steady mains hum. Lift the ground on the DI box (most have a ground-lift switch) to break the loop.
- Riding the fader to fix a quiet channel. If a channel is weak, the fix is almost always at the gain stage, not the fader. Pushing the fader up only amplifies noise along with the signal.
- Skipping the soundcheck order. Set every input’s gain individually with the others muted, then build the mix. Trying to balance everything at once while levels drift makes it impossible to find the problem channel — our step-by-step soundcheck guide walks through the order.
How to choose your connection method
If you only remember one rule, make it this: when a source is high-impedance or passive, use a DI box into a mic input; when it is already line level, go straight into a line input; and when it is a microphone, plug it straight into XLR. From there, two questions decide the details. First, how far is the source from the mixer? Long runs favour balanced XLR through a DI or snake, because unbalanced quarter-inch cables pick up noise over distance. Second, do you want the captured character of an amp or the clean direct sound? Micing a cabinet gives you the amp’s tone and room; a DI gives you a clean, consistent signal that is easy to mix and free of stage spill. Many players run both and blend them at the desk for the best of each.
Frequently asked questions
Can I plug a guitar straight into a PA?
You can physically, using a quarter-inch to XLR adapter, but the impedance mismatch usually gives a thin, dull tone and noise. A DI box solves this and is the standard approach.
Do keyboards need a DI box?
Not strictly — most keyboards output line level and can go straight into a line input. A DI is only needed for very long cable runs or to convert to balanced XLR.
Why is my instrument so quiet through the PA?
Almost always a gain problem or wrong input type. Check the channel trim, make sure a line-level source is on a line input and a mic/instrument source has enough preamp gain, and confirm the channel is not muted.
Can I run several instruments into one channel?
It is best to give each instrument its own channel so you can set gain, EQ and level independently. If you are short on inputs, a small sub-mixer can combine sources first, but you then lose individual control at the main desk, so keep anything that needs careful balancing on its own channel.
