Sonos Ace – Severe electrical interference when using the official USB-C to 3.5mm cable (noise reacts to nearby phone, not connected)

Hi everyone,

I’m experiencing a serious and fully reproducible issue with my Sonos Ace headphones when using the official USB-C → 3.5mm cable provided in the box. I’m posting here to understand whether this is a known issue and if there is any official guidance or fix.

What’s happening

• When using the headphones with the USB-C → 3.5mm cable, I hear constant electrical noise / buzzing / interference.

• The noise gets noticeably worse when:

  • I touch or move a phone that is nearby

  • That phone is charging

  • The phone is close to other power cables or chargers

Very important clarification

• The phone causing the interference is NOT connected to the headphones in any way.

• The phone is not paired via Bluetooth, not connected by cable, and not being used as an audio source.

• It is simply lying next to me, charging.

• When I pick up or touch that phone, the noise in the headphones immediately increases.

• When I move the phone away, the noise decreases.

This strongly indicates electromagnetic / grounding interference affecting the analog signal path, not a device or connection issue.

Very important comparison

• If I use the USB-C → USB-C cable (the one intended for charging), I can listen to audio with no interference at all.

• Bluetooth audio is also perfectly clean.

• This strongly suggests:

  • the headphones themselves are not defective

  • the issue is specific to the analog audio path, most likely the USB-C → 3.5mm cable, its DAC, grounding, or shielding

Additional details

• This issue happens across multiple devices used as audio sources.

• It only occurs in analog wired mode.

• The Ace headphones only recognize the original Sonos cable, so I can’t test third-party cables to further isolate the problem.

• The fact that the noise reacts to touching an unrelated, nearby charging phone makes this feel like a hardware / shielding / grounding design problem, not software.

What I’ve ruled out

• Not a single-device issue

• Not Bluetooth-related

• Not USB-C digital audio related

• Not volume, EQ, or ANC related

• Not user error — the behavior is consistent and easily reproducible

Why this is concerning

For headphones in this price range, wired listening should not be affected by:

• touching an unrelated device nearby,

• a phone charging next to you,

• environmental electrical noise that disappears entirely in digital modes.

Since Sonos requires the use of the official cable only, there is currently no workaround if the analog cable itself is the source of the problem.

Questions for Sonos / community

1. Is this a known issue with the Sonos Ace analog wired mode?

2. Is there any firmware update planned to improve analog noise immunity?

3. Has Sonos identified faulty batches of USB-C → 3.5mm cables?

4. Is this expected behavior, or should I pursue an RMA / replacement?

I’m happy to provide additional details or run specific tests if needed.
Thanks in advance — I’m hoping for an official response, because at the moment the analog wired mode is unusable for me.