yet another laptop noise problem - hdmi |
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APW
Young Croc Joined: 13 November 2012 Location: Kent, UK Status: Offline Points: 1173 |
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When I had my repair business I regularly had mixing decks
in with input channels blown due to the DJ removing the laptop psu ground to solve this
issue then plugging the laptop into the grounded mixer!! As Kevin correctly pointed out the problem
with class 1 psu is that they have a higher leakage current than the
non-earthed class 2 supplies (3.5mA leakage for class 1 IT equipment, 0.25mA
for class 2), and when the earth is disconnected the output from the PSU sits with
115-120Volts leakage on the output (although at low current: @ up-to 3.5mA), when
the laptop is then plugged into a grounded piece of equipment the 115-120Volt
leakage is then dissipated to ground via the equipment often frying it in the
process.
Edited by APW - 05 February 2019 at 8:19pm |
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godathunder
Old Croc Joined: 19 July 2004 Location: wicklow Status: Offline Points: 1833 |
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I see your point do you feel studio45s suggestion of running a bond to the laptop/psu 0v rail is a sensible one? I assume that it isnt done because my laptop would no longer be a class 2 device which no doubt has ramifications in compliance
Edited by godathunder - 05 February 2019 at 9:20pm |
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LOUDER THAN LOUD
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fatfreddiescat
Young Croc Joined: 15 October 2010 Location: N.E.Wales Status: Offline Points: 1081 |
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In the past I have just hunted down a class 2 laptop psu on fleabay with the same voltage and current specs, chopped the end off my old psu and soldered it to the class 2.
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djscooby
Young Croc Joined: 15 March 2008 Location: United Kingdom Status: Offline Points: 1414 |
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I had the issue with this noise through headphone socket through d.i box into desk I tried the naughty remove earth wire the actual PSU didnt work
I removed the earth in the XLR connections and that cut it out but now use a usb sound card as well now nothing spectacular but it does the job
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Well my wife has kicked me out saying it's over due to my obsession with speakers don't know watt I'm gonna do with no ohm to go to
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studio45
Old Croc Joined: 16 October 2007 Location: United Kingdom Status: Offline Points: 3863 |
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For a year or so I had an aftermarket, "double-insulated" (no earth pin) supply for my Macbook that worked as a bad neutral detector - if the neutral was even slightly higher impedance than it should be, you'd get a LOVELY 160v AC measurable on the laptop's metal casing, and a detectable "zap" if you touched it while well-grounded. God only knows what it was doing to the DC-in board. At other times, no problem. I thought it was an intermittent fault until I realised it only happened in certain buildings. Oddly though, it never gave a me noise on the audio.
But then, it did only cost £13 delivered, as opposed to £90+ for a real Apple unit. I was about to add a ground wire to it, then it died completely, so I just got another one, and that doesn't do it at all!
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Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
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Djdarch
Old Croc Joined: 10 November 2005 Location: Newark, Notts Status: Offline Points: 1989 |
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what model laptop is it ? dells for example the older laptop PSU's had no earths and work fine on the newer laptops .
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mini-mad
Old Croc Joined: 13 July 2012 Location: london Status: Offline Points: 6903 |
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This.
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If it sounds like a gorilla is trying to escape, turn it down.
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godathunder
Old Croc Joined: 19 July 2004 Location: wicklow Status: Offline Points: 1833 |
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an obvious bodge solution presented itself
laptop direct to tv (class 2) via hdmi tv to decoder via optical nasty noises has done goned still passes 5.1 audio in most formats Im likely to need although Im not going to be able to pass the higher resolution formats (not that makes a lot of difference given the state of my hearing) btw, on the subject of higher res formats, does anyone know of a dirt cheap hdmi extractor decodes dsd to dolby digital or similar? I picked one of these up which suggests dsd compatibility but doesnt seem to support it in practice |
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LOUDER THAN LOUD
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