Audio Impedance
Overview
Impedance is electrical resistance to an audio signal. It is measured in ohms, shown with the omega symbol: Ω.
In audio systems, impedance affects sound quality, signal strength, noise and interference, and whether equipment is matched correctly.
Low Impedance and High Impedance
Low Impedance, also called Lo-Z
Typical range: 50 Ω to 600 Ω
Low impedance is commonly used with microphones, professional audio gear, mixers, and audio interfaces.
Key features
- Provides a strong, clean signal.
- Helps reduce noise and interference.
- Works well for long cable runs.
- Often uses balanced XLR connections.
High Impedance, also called Hi-Z
Typical range: 10 kΩ to 1 MΩ
High impedance is commonly used with electric guitars, bass guitars, passive pickups, and instrument inputs.
Key features
- Designed for instruments.
- Requires a proper Hi-Z or instrument input.
- Is not ideal for long cable runs.
- Can be weak or sensitive compared with professional low-impedance signals.
Quick Comparison Chart
| Category | Low Impedance, Lo-Z | High Impedance, Hi-Z |
|---|---|---|
| Common sources | Microphones and professional audio systems | Guitars and instruments |
| Typical connector | XLR | Quarter-inch TS instrument cable |
| Cable length | Long runs are usually acceptable | Short runs are preferred |
| Noise resistance | High | Low |
| Signal behavior | Strong | Weak or sensitive |
| Typical equipment | Mixers, interfaces, microphones, and pro audio gear | Passive pickups and instrument inputs |
DI Box Example
A DI box can convert a high-impedance instrument signal into a low-impedance balanced signal. For example, an electric guitar can connect to a DI box, and the DI box can send an XLR output to a mixer or audio interface.
Why Proper Matching Matters
Using the wrong input can cause weak volume, dull tone, extra noise, hum, or signal loss. A microphone should usually connect to a microphone input. A guitar or bass should usually connect to an instrument input or a DI box.
Important: Do not assume that every quarter-inch input is correct for every instrument or audio device. Check whether the input is labeled instrument, Hi-Z, line, or mic.
Setup Checklist
- Identify the source: microphone, guitar, bass, keyboard, mixer, or playback device.
- Choose the correct input: mic, instrument/Hi-Z, or line.
- Use XLR for most professional microphone connections.
- Use shorter cables for high-impedance instrument signals.
- Use a DI box when sending a guitar or bass signal over a long distance.
- Listen for hum, noise, weak level, or loss of tone.