High-Pitched Noise in Right Ear of DJM-900NXS Headphones Output

Hello,

I am experiencing an issue with my Pioneer DJM-900NXS mixer and would appreciate any insights or solutions. The problem is as follows:

Issue Description

• Symptom: A high-pitched noise, similar to a fan, is audible in the right ear of my headphones. This noise appears intermittently after a sound is played. Here is a link to a recording of the sound. The low buzz you hear in this recording is only present in the recording and is not heard on the headphones.
• Behavior: The pitch of the noise slightly varies and is unaffected by any of the volume knobs or faders on the mixer. The noise persists until the mixer is rebooted or the headphones are unplugged and replugged.
• Occurrence: The noise does not always start with the first sound input. When the issue starts, it continues until the mixer is rebooted or the headphones are reconnected.

Troubleshooting Steps Taken

1. Power and Connections:
   
   • Disconnected all cables from the mixer except for the power cable.
   • Tested the mixer on a different mains power source.
2. Grounding:
   
   • Attempted grounding the mixer to the mains ground and to a radiator. Connecting to mains ground worsened the issue, while connecting to the radiator showed no improvement.
   • Measured resistance between the radiator and mains ground, which is approximately 0.7 ohms.
3. Headphone Testing:
   
   • Using a stereo-to-mono jack converter eliminates the noise. Additionally, the master/cue balance knob needs to be set at 75% towards master to achieve balanced volume levels between cue and master on the headphones.
4. Jack and Cable Inspection:
   
   • Tested different headphones, jack converters and cables to rule out a problem with the headphone connection.
   • Cleaned the headphone jack with contact cleaner.

Additional Information

• The issue seems to be linked to internal components or grounding within the mixer, as it is not resolved by changes in power source or external grounding.
• The problem is not apparent when using a mono jack converter, indicating a potential issue with the stereo output or headphone circuitry.

Request for Assistance
I am seeking advice on:

• Potential internal faults that could cause this issue.
• Further troubleshooting steps or methods to identify the source of the problem.

Thank you for your assistance.