A hum is a steady, low-frequency tone (usually 50 Hz) that can be heard regardless of volume or playback content.
Most common causes:
- Ground loops
- Interference in the power grid (e.g. from dimmers, chargers, power supplies, or other devices)
- Poorly shielded or defective audio cables
- Different grounding of connected devices
- In rare cases: a defect in the subwoofer or power supply
Reading tip: Guide on our blog: How to stop your subwoofer humming.
How can I check where the humming is coming from?
Step 1: Unplug the RCA cable from the subwoofer’s input jack.
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Hum remains → The issue is with subwoofer or the power supply → see Check power supply
- Hum disappears → The issue is with the connected audio system → see Check ground loop
Step 2: Check power supply
Temporarily connect only the subwoofer to an outlet on a different circuit (e.g. kitchen, bathroom, or bedroom).
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If the subwoofer still hums, please contact our support.
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If the hum disappears, the interference is very likely caused by another device on the original circuit (e.g. dimmers, chargers, or power supplies).
- Now unplug all devices on the original circuit one by one from the power supply (e.g. dimmers, chargers, power supplies, or other devices).
- As soon as the hum disappears, you have identified the interfering source. You can now connect this device to a different circuit or eliminate interference through appropriate measures (e.g. with a power line filter, interference suppression socket, or a high-quality power supply). Alternatively, replacing the device may be advisable if it clearly proves to be the source of interference and the problem cannot be resolved otherwise.
Step 3: Check ground loop
A ground loop occurs when multiple devices are connected to each other through both power and audio cables, creating a difference in ground potential. This can result in an audible hum.
Here’s how to identify the source of interference:
- Disconnect the cable or satellite connection line from the TV or AV receiver and check if the hum disappears.
- For a cable connection, it is best to use a common-mode choke filter to eliminate the interference.
- For a satellite connection, if possible, connect the receiver to the playback source via an optical audio cable.
- If the hum continues, please disconnect all connected devices from the AV receiver one at a time until the hum stops.
- The last device you disconnected is the cause of the ground loop. You can test this device on a different circuit or eliminate interference through appropriate measures. If the interference cannot be eliminated, replacing the device is advisable.
What solutions are available?
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Galvanic isolation in the signal path
These are among the most effective solutions, as they break the electrical ground path without affecting the audio signal:- Common-mode choke filter: Particularly effective for cable TV or antenna connections. It galvanically isolates the antenna line ground and very often eliminates hum.
- Audio isolation transformer / ground loop isolator: inserted into RCA, jack, or XLR connections. It breaks the ground loop directly in the signal path.
- Optical audio connection (TOSLINK): Since light is used instead of an electrical signal, ground loops cannot occur.
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Common power supply
Operate all involved devices from one outlet or a common power strip to avoid ground potential differences. In some cases, a different circuit may also help, but this is not a guaranteed permanent solution. -
Optimize devices and connections
Identify the problematic device (as described above, e.g. by disconnecting devices one by one) and eliminate interference specifically. Use high-quality, well-shielded cables and avoid unnecessarily long cable runs. -
Replace device (if necessary)
If a device is poorly decoupled by design, uses a low-quality power supply, or causes persistent ground loops, replacing it may be the only viable permanent solution.
When is a defect likely?
Your subwoofer may be defective if the hum is audible even when no audio cable is connected and the subwoofer is only plugged into the power supply.
Please contact our customer support in that case.