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Laptop into mixer is buzzing

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David Aberdeen:
In our church sound system, we use a Macbook for the presentations, which sometimes include video/audio clips.  About half an hour into the service, this channel develops a buzzing noise.  I'm trying to work out where this noise may be coming from, and how to prevent it.

The laptop is connected through the headphone port (3.5mm stereo) , through to 2xRCA plugs at the mixing desk input.  The headphone to RCA cable is about 3m long, and not shielded.  It is run along a cable tray with lots of other cables, including power.  When first setup, it is fine, with no noise, but at some random point during the service, it develops a constant buzzing noise (not 50Hz), and requires that we turn off the laptop sound channel when it's not needed.  The laptop is not connected to power, and just runs off battery.  At the mixing desk, we have options for XLR inputs.

Is it possible to get (or build) a passive shielded cable to take the 3.5mm headphone jack through to XLR inputs?
Is this likely to help?
Is there a better way?  I know we could take the headphone signal through a stereo DI box and convert to balanced, but I'd like to avoid that extra cost/complexity if all it needs is a cable.

Dave Pluke:

--- Quote from: surfdabbler on November 07, 2022, 06:44:03 PM ---Is there a better way? 

--- End quote ---

Probably. First, Check the Rules, Change your ID to your real name.  Then, we might be able to offer some suggestions.

Dave

Tracy Garner:

--- Quote from: David Aberdeen on November 07, 2022, 06:44:03 PM ---In our church sound system, we use a Macbook for the presentations, which sometimes include video/audio clips.  About half an hour into the service, this channel develops a buzzing noise.  I'm trying to work out where this noise may be coming from, and how to prevent it.

The laptop is connected through the headphone port (3.5mm stereo) , through to 2xRCA plugs at the mixing desk input.  The headphone to RCA cable is about 3m long, and not shielded.  It is run along a cable tray with lots of other cables, including power.  When first setup, it is fine, with no noise, but at some random point during the service, it develops a constant buzzing noise (not 50Hz), and requires that we turn off the laptop sound channel when it's not needed.  The laptop is not connected to power, and just runs off battery.  At the mixing desk, we have options for XLR inputs.

Is it possible to get (or build) a passive shielded cable to take the 3.5mm headphone jack through to XLR inputs?
Is this likely to help?
Is there a better way?  I know we could take the headphone signal through a stereo DI box and convert to balanced, but I'd like to avoid that extra cost/complexity if all it needs is a cable.

--- End quote ---


On the 3.5mm does it have 1 or 2 black rings? You can usually do it without going to a balanced DI Box but in a church, I would rather go the DI route - even passive. If you search around the forums here, you will see several recent threads with suggestions for boxes from $20 to a couple hundred depending on what you are trying to accomplish.

Nathan Riddle:
Purchase a Peavey USB-P USB Playback Device and be done with the whole ordeal.

Everything else is a compromise.

Mac Kerr:

--- Quote from: Nathan Riddle on November 08, 2022, 09:57:48 AM ---Purchase a Peavey USB-P USB Playback Device and be done with the whole ordeal.

Everything else is a compromise.

--- End quote ---

^^^^^THIS^^^^^

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