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90% buzzing 10% Audio-- laptop to headphone amp -- Need help--

Discussion in 'Recording' started by brian8084, Feb 15, 2013.

  1. brian8084

    brian8084 Active Member

    HI,

    The Setup:
    I am using a laptop for my DAW/Sound output to my Headphone distribution amp. The laptop output is a headphone output not a line-out output. My Headphone amp has a 1/4 stereo direct input and the laptop has a 1/8 output. I use a 1/8 to 1/8 cable with a 1/8 to 1/4 stereo to stereo adapter.

    The Problem:
    When the laptop is Plugged into the Headphone Amp I get a massive AC hum. Can hardly hear the music.

    Symptoms:
    I have tried a 1/8 to 1/4 stereo to stereo adapter, 1/8 to 1/4 Stereo to mono adapter and 1/8 to 1/4 mono to mono adapter on the amp with no change.

    I have tried pulling out the 1/8 cable slightly and the buzzing goes completely away but when I talk into my Mic I can only hear the reverb effects. Its like canceling out my voice other then the reverb. The only way I can get rid of this is to turn the master channel pan fully to the left or the right. Thats cool but I loss all my stereo effect.

    When plugging headphones directly in to the laptop the sound is crystal clear.

    1/8 to 1/8 cable was tested to be fully working.

    Also tried connecting the output to the balanced inputs on back of the headphone amp. same problem. Tried stereo to mono adapter mono to mono etc.

    Like I said before, the only way I can get 90% clear sound is to slightly pull out the 1/8 cable connected to the 1/4 stereo to stereo adapter. but then get a canceling affect so have to pan master to full left or right.

    I have a feeling it may have something to do with the laptop output not being a true line-out but I have used other headphone jacks this way without problem.

    Any Ideas?
    Thanks,
    Brian
     
  2. kmetal

    kmetal Kyle P. Gushue Well-Known Member

    buy pulling out the cable slightly your turning a stereo (trs) cable into a guitar type cable (ts). that's what your pan thing is, you could just (if your headphone amp has it) press the mono button on the channel, that'll put it out thru both sides.

    i'd double check the cable your using, make sure it works the way it should. what your doing is not ideal, but it certainly can work. providing the cables work, and there aren't any strange power issues, all you have to do is make sure you don't put the headphone out so high/loud that you distort the headphone amp in. i suspect a bad cable, or incorrect connection.
     
  3. brian8084

    brian8084 Active Member

    I have tried the mono buttons on the amp still same buzz.

    When I disconnect the 1/8 to 1/8 cable from the laptop and have it fully connect to the headphone amp I can hear left buzz when touching the other side of the plug as well as the right side of the headphones. So both connection of the cable seems to be getting signal.

    But in anycase Im thinking that 1/8 cable may be bad as it is having problems in other applications.

    Going out to get a new cable, hope that fixes.

    Thanks
     
  4. RemyRAD

    RemyRAD Well-Known Member

    It really sounds to me like you have a twofold problem going?

    Firstly, 1/8 inch TRS plugs are all notoriously simply awful. The best in intermittency. So you get some gold plated ones and replace those nice shiny chrome ones with the gold plated ones. Do that first. If you can purchase them premade? More power to ya. If not? Time to get out the soldering iron and order some good goldplated plugs.

    Secondly, there are huge problems with ground Loop hum when most anything gets plugged into the computer that happens to be plugged in to another wall outlet somewhere else in your room. And even if they are plugged into the same outlets, ya get a ground loop on that 1/8 inch cable. So you can lose the plug and the wire grounded on the source feeding side. And disconnect the ground wire from the plug on the input receiving side. Or, you could simply take your computer power cord plug and insert a 3 into 2 AC ground lifter. And most of your problems should then be solved. Beware though, any guitar amplifiers with tubes that have had their AC plugs screwed around with them the ground pin removed, with a new one replacing the old one but wired backwards, can pose a deadly shock hazard. Nothing to screw around with if you don't own an AC voltmeter. And ya make absolutely certain when you plug things in to check the ground on one device against the ground on an other device. You will still likely find some voltage? It should be fairly low. Though you could see it as high as 60 V. As long as you're not looking at 110 V or, 220 V elsewhere in the world, you should be good to go. But you'll also want to make that same test and check if anyone else brings in their own guitar amplifiers. You just simply connect one test lead to the metal housing of a plugged in microphone. And you connect the other test lead to the chassis ground of the unknown guitar amplifier. You don't want to kill any of your clients. So don't be lazy. Don't be too self-assured. Never assume that nothing will happen.

    Can't get enough of that funky stuff.
    Mx. Remy Ann David
     
  5. pcrecord

    pcrecord Don't you want the best recording like I do ? Well-Known Member

    I bet when you unplug the laptop powersupply most of the noise go away. using a ground lift can help + make the laptop output to its maximum volume and lower the gain of your headphone amp. it'll be better.

    but remember the headphone output is a preamplified signal not ment to be amplified again.

    Radial made a DI for that exact reason : Radial JPC? - Computer Direct Box
     

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