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Audio Interference with high wattage devices on the same circuit?

YallYall Registered User regular
So I have an AV problem which I *think* is related to a power/electrical issue:

I'm have an Optoma HD20 projector with an HDMI signal coming in and I'm trying to connect the audio out (1/8th) to a Yamaha DSR112 12 Inch Powered PA Speaker. However, the audio signal is relatively weak and very buzzy/scratchy.

I've tried connecting other devices (with the same cables) to the PA speaker, and it sounds great.
I've also tried connecting other devices to the audio out (old low wattage PC speakers, multiple headphones etc.) also sounds great.
I've tried several different cables, etc to connect the PA speaker and the projector, all with the same issue (washed out audio with lots of noise/interference).

In short the only thing that doesn't sound good is any connectivity between the two devices.

The only conclusion I'm able to come to is that because both the speaker and projector are presumably higher wattage devices , and both on the same breaker/circuit, that I've got some type of phase issue or something like that going on due to them being on the same circuit.

Does this seem like a reasonable conclusion?


  • BlazeFireBlazeFire Registered User regular
    Might be a ground loop. Can you try an audio cable with a ferrite core on it?

  • YallYall Registered User regular
    BlazeFire wrote: »
    Might be a ground loop. Can you try an audio cable with a ferrite core on it?

    I think you may be right. Furthermore they might be on different circuits so I'm gonna try the same outlet.

  • BlazeFireBlazeFire Registered User regular
    Different circuits would support the ground loop idea.

    How long is the audio cable, btw? Is it possibly picking up interference?

  • Marty81Marty81 Registered User regular
    edited August 2017
    I would guess that using balanced audio cables would eliminate your problems, but I don't know if your projector has balanced audio out capability. Internal amps on powered speakers tend to run at full force regardless of your set volume level and the noise on the line is likely coming from the projector itself, so that's why you hear it on the yamaha and not on your old pc speakers. The noise is still there, but the pc speakers aren't cranked up loud enough to hear it.

    I just realized this makes no sense. If the noise is coming from inside the projector, which I still suspect it is, then balanced output would not help. I had this exact same problem with a computer to powered speaker connection and what solved it was getting a USB DAC, and while that included upgrading the connections to balanced cables it's not the balanced cables that solved it.

    Marty81 on
  • YallYall Registered User regular
    Cable is short (3 feet). No option for balanced output on the projector but I would like to note that when I connect headphones or PC speakers to the audio out there is zero noise. The amount of noise on the speaker however is not just "present" but overwhelming. The actual audio signal is nearly washed out completely.

    I'm thinking it's almost certainly a ground loop. There could be other sources of interference as well, but I'll be doing a test run tonight using wireless HDMI and the same outlet. I'm hoping the combination of the two will solve the issue.

    Will let you guys know!

  • YallYall Registered User regular
    Well the test on the same outlet yielded somewhat improved results but not enough. I will try a much nicer shielded cable when Amazon delivers it tomorrow, but I may need the backup plan (PC speakers). Less than ideal (outdoor pool party with the fight in HD on a 16'x9' screen) but they'll suffice.

    Thanks for all the advice!

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