Overview

A headphone audio test helps isolate missing, incorrect, distorted, or intermittent audio by listening directly to a Just Add Power device's analog stereo output. Test the output feeding the affected sound system to determine whether to investigate the Just Add Power audio path or the connected analog cable and equipment.

This procedure applies to Omega Series, Ultra Series, and MaxColor Series models equipped with an analog stereo output, including an ST1 operating as a Decoder in those systems. Check the model's specifications for its output connections and supported features.

For broader troubleshooting, including problems affecting both audio and video, see Troubleshoot a Just Add Power System.

Before You Begin

Identify the Audio Output Being Used

Trace the analog audio cable from the affected amplifier, audio processor, analog audio matrix, or powered speakers back to the Just Add Power device. Perform the headphone test at that device's output.

Identify where the intended audio originates and how it reaches this output:

• Encoder extraction: Audio comes from the Encoder's connected source or selected audio input, where applicable.
• Decoder extraction: Audio comes from the source selected for that Decoder. A separate Decoder or ST1 may supply room audio independently of the Decoder serving the TV. See ST1 Audio Distribution Examples for dedicated audio applications.
• Multicast Switching: Flexible Mode allows audio to be selected independently of video; Unified Mode switches them together. In Flexible Mode, the displayed picture does not establish the selected audio source. See Multicast Switching Protocol for modes, Channel assignments, and switching controls.
• Standardized Configuration: Normal Encoder audio and video switching remains paired at each device. The room's sound system may still use a separate extraction device or downstream audio routing. MaxColor Series ARC provides another audio source, as described below.

MaxColor Series ARC: In both Standardized and Alternate Configuration, supported MaxColor Series Decoders can receive audio from a display and distribute it to other supported MaxColor Series Decoders. The Decoder connected to the display acts as the Broadcaster; the Decoder receiving that audio acts as the Subscriber. Identify both devices and the intended Broadcast Channel. See Audio Return Channel - Setup and Control for model, firmware, and configuration requirements.

Check Audio Through the TV Speakers

When troubleshooting a source connected to an Encoder, check whether that source plays through the internal speakers of a TV connected to a Decoder. Confirm that the TV is playing the intended audio, not merely showing the intended video.

• TV audio works: Audio from the source is reaching that TV through the Just Add Power system. Investigate the analog extraction path feeding the affected equipment. If it uses a different Decoder or ST1, verify that device's audio selection and reception separately.
• TV audio does not work: The problem has not been isolated to analog extraction. Check source playback, audio selection, format compatibility, and the TV's speaker settings.

For ARC audio originating at the TV: Hearing an internal app through the TV speakers confirms local playback only. It does not confirm that the TV is sending ARC audio to the Broadcaster or that the Subscriber receives it. Check the ARC path separately. Restore any TV audio-output setting changed for the speaker test before testing ARC.

Perform the Headphone Test

Use known-working wired stereo headphones. Most models provide a 3.5 mm analog audio output; some use a Euroblock/Phoenix connector. For those models, use a compatible adapter wired according to the model's documented analog output pinout. Verify the headphones and adapter on a known-working output before interpreting the results.

1. Reproduce the reported audio problem. Play the intended source and confirm the symptom through the installed sound system. Record whether audio is missing, from the wrong source, distorted, intermittent, or missing a channel.
2. Check the extraction device's webUI. Follow How to Open the webUI of a Device, then record the incoming audio format and channel count, where shown. Verify the selected input or audio source. For ARC, check that the Subscriber is receiving the intended Broadcaster's audio rather than Encoder audio.
3. Confirm that two-channel LPCM is available for extraction. Account for any downmixing before changing the source:
   • UL-718AVP and UL-749AVP: Accept stereo LPCM or Dolby Digital up to 5.1 channels and downmix supported Dolby Digital audio to two-channel LPCM.
   • UL-718KVM and UL-749KVM with the downmixing chip installed: Provide the same downmixing capability. The KVM model number alone does not establish that the chip is installed.
   • Devices without downmixing: Must receive two-channel LPCM for analog extraction. That signal may already have been downmixed by an upstream Encoder.

   A downmixing Encoder may report Dolby Digital at its input while producing two-channel LPCM. Do not interpret that input reading alone as an incompatible analog-output format. See Dolby Audio Downmixing - Specifications for supported models and formats.

   If the format is unsuitable, record the original setting and select stereo PCM/LPCM at the source. For ARC, check the TV's ARC audio-output format. Confirm the resulting audio details in the receiving device's webUI. This change can affect every location using that audio source.

4. Connect headphones to the analog output. Label and disconnect the installed analog audio cable from the Just Add Power device. Connect the headphones to that same output, using the appropriate adapter where required. Keep HDMI and network connections in place.
5. Listen for the intended source and reported symptom. Record whether the audio is clear, silent, from another source, distorted, intermittent, or missing a channel. If you hear a loud pulsing or chopping noise, remove the headphones and follow Helicopter Sound Instead of Audio.
6. If the output is silent, check its supported controls. Where the model provides analog output mute or volume control, confirm that the output is unmuted and its level is not at minimum. Record settings before changing them. Use the model-specific controls in Analog Audio - Features & Commands, then repeat the listening test.

Compare the result with the findings below. Differences in headphone loudness between devices are not, by themselves, evidence of a fault.

Interpret the Results

The TV-speaker comparisons below apply to audio delivered from an Encoder through a Decoder to the TV. For audio originating at the TV through ARC, verify Broadcaster and Subscriber operation separately.

Audio Plays from the Wrong Source

Recognizable audio from another source confirms that the analog output is producing audio. Investigate source selection and routing.

1. Confirm that you are testing the Just Add Power device whose analog output feeds the affected equipment.
2. Encoder extraction: Verify the connected source and selected audio input, where applicable. The Encoder's analog output does not follow the source selected at the TV.
3. Decoder or ST1 extraction: Verify the source selected for that device. In a Multicast Switching system using Flexible Mode, check the audio Channel separately from video. In a Standardized system, a dedicated audio device may be selected to a different source from the TV's Decoder.
4. MaxColor Series ARC: Check whether the Subscriber should play Encoder audio or ARC audio. For ARC, verify the selected Broadcast Channel and the display connected to that Broadcaster.
5. If the headphones play the intended source but the room speakers play another, check downstream input selection and zone routing.
6. If the correct audio plays only temporarily, check whether the control system sends another source-selection or routing command.

Distorted or Intermittent Audio

If the headphones reproduce the distortion or dropout, the symptom occurs with the installed analog cable and downstream equipment disconnected. Investigate the source, extraction device, and any network path carrying that audio.

If another compatible analog output is available, monitor the same audio there:

• The symptom occurs at both outputs: Investigate the source and shared audio path. This may include the source Encoder or, for ARC, the display and Broadcaster.
• The symptom occurs at only one output: Investigate that device's settings and analog output. If it receives audio over the network, also check the path delivering audio to it.

Check network link speeds: An Encoder or Decoder connected at 10 or 100 Mbps instead of its expected 1 Gbps can cause audio and video interruptions. Use AMP Gather Details and the switch's port status to verify the links involved. If a reduced speed is reported, follow Encoder or Decoder Connected at 10/100 Mbps to isolate the device, cable path, or switch-port problem.

Apply network checks to the path carrying the affected audio. A local Encoder analog output and a Decoder receiving audio across switches do not use the same signal path. If endpoint links are healthy but affected devices share an inter-switch connection, use Plan Network Bandwidth for Just Add Power Systems to evaluate shared capacity. For Standardized systems, also verify the interconnect requirements in Multi-Switch Considerations for AMP Standardized Systems.

For intermittent problems, repeat the comparison under the conditions that originally caused the symptom. A brief test without a dropout does not confirm that the problem is resolved.

One Audio Channel Is Missing

A missing left or right channel can result from feeding multichannel LPCM to the device performing analog extraction. It can also indicate a connector, termination, or cable problem.

1. Check the extraction device's incoming audio details. Confirm that the audio available for extraction is two-channel LPCM rather than multichannel LPCM.
2. If multichannel LPCM is reported, record the original output setting and select two-channel PCM/LPCM at the source or TV supplying ARC audio. Confirm the change in the webUI and repeat the headphone test.
3. If one channel is still missing, use content known to contain both left and right audio. Verify both headphone channels on another output.
4. Fully seat the 3.5 mm connector or check the Euroblock/Phoenix adapter wiring against the model's documented pinout.
5. If both channels work through the headphones, investigate the installed analog cable, terminations, and downstream equipment. If one channel remains missing at the device's output, compare another compatible output playing the same source.

Helicopter Sound Instead of Audio

A rapid pulsing or chopping noise resembling a helicopter can occur when encoded audio, such as Dolby Digital or DTS, reaches the analog output without conversion to two-channel LPCM. This differs from a missing channel caused by multichannel LPCM.

1. Remove the headphones from your ears before continuing.
2. Check the incoming audio details for an encoded format such as Dolby Digital or DTS.
3. If the format is not supported by the downmixing hardware in the audio path, record the original setting and select two-channel PCM/LPCM at the source or TV supplying ARC audio.
4. Confirm the changed format in the receiving device's webUI, then repeat the headphone test at a safe listening level.
5. If supported Dolby Digital audio should be downmixed but the noise continues, record the model, incoming audio details, and installed downmixing hardware for Just Add Power Technical Support.

Dolby Digital downmixing support does not establish support for DTS, Dolby Digital Plus, or other encoded formats. Use the model and format requirements listed earlier in this procedure.

Audio Returns After Reconnecting the Cable

If the original equipment works after reconnecting its analog cable, inspect the plug, socket, cable, and adapters. A connection changed during testing, but the cause is not yet confirmed. Repeat the original operating conditions and monitor for the problem returning.

Finish the Test

1. Remove the headphones and reconnect the original analog audio cable.
2. Restore temporary source selections, audio-format settings, TV speaker or ARC settings, and device output settings unless a corrective change has been confirmed and documented.
3. Verify audio through the equipment the customer normally uses, including other locations affected by the changes.
4. For an intermittent problem, repeat the activity that originally caused it and check whether the symptom returns.

If the results point to one Encoder or Decoder, follow How to Perform a Device Swap Test, using a replacement compatible with the required audio features, to check whether the symptom follows the device or remains at its location.

If further assistance is needed, provide Just Add Power Technical Support with the device models, incoming audio details, selected input or source, analog output connection, and headphone results. Include any downmixing hardware, ARC roles and Broadcast Channel, changes made during testing, and whether two-channel LPCM resolved the symptom.