MBP Buzzing speakers through headphone jack

Discussion in 'MacBook Pro' started by digitalpencil, Feb 3, 2008.

  1. digitalpencil macrumors 6502

    digitalpencil

    Joined:
    Jul 2, 2007
    Location:
    Manchester, UK
    #1
    Hi, my MBP is making a buzzing noise audible through my speakers, connected via a mini-jack to phono from the headphone jack. I originally thought the noise was a ground loop but i've tried plugging both my amp and laptop into the same wall-socket and it still buzzes, even when the laptop is running off battery. The phono cable is fine and produces no noise when connected to my iPod. The headphone jack also produces no noise through my headphones.
    What could be causing this buzz? I think it's processor whine as it changes depending on whether windows are maximized or if i'm scrolling a page etc.
    Not sure if it's relevant but comp is an MBP SR, connected via mini-jack to phono to a Marshall AS50r acoustic amp. Any ideas on how to alleviate are greatly appreciated, it's pretty annoying!
     
  2. superleccy macrumors 6502a

    superleccy

    Joined:
    Oct 31, 2004
    Location:
    That there big London
    #2
    Don't know if my experience is related, but I had a helluva load of noise (buzzing, squelching, etc) coming out my external speakers connected via the analogue headphone jack.

    I traced the source of the noise from my MBP, through the FW400 cable to my Cinema Display, through FW again to my Elagto EyeTV 410, then through coax into the terrestrial TV socket in my upstairs den, under the floorboards, through the wall, down the outside of my house, back in to my living room, under the floor again, into the back of my LCD TV, and from there into all manner of interconnected home entertainment nonsense.

    The thing is, I've plenty of audio gear plugged into this rats nest of technology, but the MBP was the only device picked up noise like this. I checked all my earths, upgraded my coax cables, even got mains cleaners. I dismantled all the electrical devices in my house. I went completely insane. No improvement.

    I fixed it in the end - sort of. I got a D/A converter from Ebay (Beresford TC-7510 - about £100 - highly recommended) and run my audio out through that using SPDIF. Noise can't travel in optical fibre! Just get pure audio now... sounds great.

    I think there's something about the MBP that makes it pick-up and amplify every bit of electrical noise in the neighbourhood. Can't think of any other explanation.

    SL
     
  3. digitalpencil thread starter macrumors 6502

    digitalpencil

    Joined:
    Jul 2, 2007
    Location:
    Manchester, UK
    #3
    If this goes on any longer, i am going to to go insane but i don't think my flatmates would take to kindly to me ripping apart the toaster to correctly earth it either! :confused:
    I've traced the sound back to the link to my new TFT. The sound is transmitted through the DVI-VGA/VGA to the monitor. It doesn't occur when the cable is disconnected but will (quiter) when I simply touch the VGA to the DVI port on the laptop, meaning that the DVI-VGA converter is not at fault either. I've also tried another VGA cable but it's exactly the same.
    One thing i've noticed is that the noise is only produced when the laptop is sending a video signal, when the display settings are being refreshed (blue screen) the noise disappears. Although this doesn't explain why there is a lower noise when the VGA touches the DVI port?
    Is this simply a matter of shielding? The TFT is sat in between the amp and the laptop. I'd rather not spend £100 on a DAC so would i be able to suppress the noise using an optical to phono converter like this: http://www.radiotronics.co.uk/item.php?partcode=A132BD&affid=froogle and then would I be able to split this into L/R as it only looks like it has one phono out, surely that'd convert the sound to mono?

    Thanks.
     
  4. iTim314 macrumors 6502

    Joined:
    Jun 5, 2005
    Location:
    U.S.
    #4
    Mine does the exact same thing. Apparently, it's a design flaw in most MPBs by having the headphone jack where it is.

    Sorry. I just hope they fix it whenever it is they decide to scrap the current design. =\
     
  5. superleccy macrumors 6502a

    superleccy

    Joined:
    Oct 31, 2004
    Location:
    That there big London
    #5
    I concur with ChexBoss32890. Design flaw. Sux. :mad:

    That item converts an optical digital signal into electrical digital signal. Unless your Amp has an electrical digital (coax) input, it's not going to do you any good.

    Don't blame you for not wanting to shell out for a DAC. It should 'just work'. I found it surprisingly hard to find one but it was the only solution I could think of. £100 is actually quite reasonable compared to some of the stuff you'll find. Alternatively... remember MiniDisc players? Some of those (particularly the Sony ones) double-up as good DACs (and ADCs for that matter)... and a second hand one shouldn't cost you too much - they're otherwise pretty obsolete.

    Or maybe get an external firewire audio interface (probably not much cheaper - and will occupy up a firewire socket).

    SL
     
  6. digitalpencil thread starter macrumors 6502

    digitalpencil

    Joined:
    Jul 2, 2007
    Location:
    Manchester, UK
    #6
    Thanks guys, have tried the firewire option with my mates Yamaha GO46 and it works fine but is about the same price as the Beresford. I do however have an old Sony MZ-R70 somewhere, screen's cracked but it does have a digital-in, would this function as a DAC? How would i get it to do this?

    Thanks again, if I can fix this with my old MD player then i'll be happy as Larry! :D
     
  7. superleccy macrumors 6502a

    superleccy

    Joined:
    Oct 31, 2004
    Location:
    That there big London
    #7
    Well, if you connect the optical-out on the MBP to the optical-in on the MZ-R70, and press its record button, hopefully it should pass-thru an analogue signal to its headphone/line-out jack. EDIT: Just had another look at the manual. Yes it should.

    Not sure what sort of digital-in is on the MZ-R70, though. If it's electrical, you're gonna need one of those gadgets after all.

    Good luck
    SL
     
  8. digitalpencil thread starter macrumors 6502

    digitalpencil

    Joined:
    Jul 2, 2007
    Location:
    Manchester, UK
    #8
    Wasn't aware that there were different types of digital-in, nt sure if it's electrical but will give it a whirl regardless. Hopefully I can wave bye-bye to my amp's case of tinnitus! Thanks again.
     
  9. superleccy macrumors 6502a

    superleccy

    Joined:
    Oct 31, 2004
    Location:
    That there big London
    #9
    http://www.minidisc.org/manuals/sony/sony_mzr70_manual.pdf

    It's got an optical line-in. So just a standard SPDIF cable will do (it'll need a minjack, or at least a minijack adaptor, on each end).

    Dunno if it'll do a straight digital-analogue pass-thru, though. You'll have to experiment.

    SL
     
  10. digitalpencil thread starter macrumors 6502

    digitalpencil

    Joined:
    Jul 2, 2007
    Location:
    Manchester, UK
    #10
    Thanks, will try it out when I find the thing and see what happens.
     

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