The Hum Is Almost Always Fixable
If your audio system is producing an unwanted hum or buzz, don't panic — and don't assume you have a faulty amplifier. The vast majority of hum problems have straightforward causes and practical solutions. Understanding what you're hearing is the first step to solving it.
Identifying What You're Hearing
The pitch of the noise gives you an important clue:
- 60 Hz hum (or 50 Hz in the UK/EU): A low, steady drone — almost always a ground loop or power supply issue
- 120 Hz buzz (100 Hz): A slightly higher, rougher tone — typically a failing filter capacitor in the power supply
- High-pitched whine or whistle: Could be interference from a switching power supply, dimmer switch, or nearby electronics
- Hiss: White noise / broadband noise — usually gain structure issues or a noisy preamp stage
Cause #1: Ground Loop
This is by far the most common cause of hum in home audio systems. A ground loop occurs when two or more pieces of equipment are connected together via audio cables and also share AC ground through their power cables, creating multiple ground paths with slightly different potentials. The difference causes current to flow through the audio cables — you hear it as hum.
How to diagnose:
Disconnect your source components (turntable, streamer, TV) one at a time. When the hum disappears after disconnecting a specific device, that's the culprit in the loop.
How to fix:
- Plug all your audio components into the same power strip or wall outlet to ensure a common ground
- Use a ground loop isolator on the offending connection (inexpensive and widely available)
- If using a cable TV or satellite connection, a cable TV ground loop isolator can eliminate hum introduced via the coax shield
- Try a balanced interconnect connection where both devices support XLR
Cause #2: Poor or Damaged Cables
A frayed, poorly shielded, or cheaply made RCA interconnect cable can act as an antenna, picking up interference from nearby electronics and introducing hum or buzz. Swapping the suspect cable with a known-good replacement is a quick diagnostic step.
Also check that all RCA connectors are fully inserted — a half-seated connection can generate noise.
Cause #3: Failing Power Supply Capacitors
If your hum is present regardless of what sources are connected and persists even with the volume control at zero, the problem is likely internal to the amplifier. Aging electrolytic capacitors in the power supply lose their ability to smooth the rectified AC voltage, allowing 100 or 120 Hz ripple to appear in the audio output.
This is a repair rather than a setup fix. A technician or experienced DIYer can measure the capacitors and replace them — a worthwhile repair on otherwise good amplifiers.
Cause #4: Dimmer Switches and Electrical Interference
Dimmer switches for lighting are notorious for injecting noise into household wiring. This noise can travel through the mains supply into your audio equipment. Try plugging your system into a different circuit — ideally one on the opposite side of the electrical panel from your lighting circuits. A quality power conditioner can also filter this type of interference.
Cause #5: Turntable Grounding
Turntables introduce a specific type of hum when the ground wire between the turntable and the phono input is missing or poorly connected. Almost every turntable has a separate ground wire that must be attached to the ground post on your amplifier or phono stage. If this wire is loose or unconnected, you'll hear a loud, prominent hum.
Quick Diagnostic Checklist
- Is the hum present with no sources connected and volume at zero? → Internal amp issue
- Does hum disappear when you disconnect a specific source? → Ground loop from that source
- Do you have a turntable? → Check the ground wire first
- Did it start suddenly? → Check for a new device added to the system or a failing capacitor
- Does moving cables make the hum change? → Shielding or loose connection issue
When to Call a Technician
If the hum persists after working through all the above, or if you suspect an internal fault in the amplifier, it's time for a professional assessment. A competent audio technician can trace the signal path with test equipment and identify whether the issue is a component failure, wiring fault, or something else entirely. Don't attempt to work inside a powered amplifier — the voltages present can be dangerous.