alistermorton Posted December 11, 2014 Share Posted December 11, 2014 If the almighty buzz disappears, you got yourself a ground loop. Or you've just killed your self! That would stop you hearing the buzz, certainly http://www.blue-room.org.uk/public/style_emoticons/default/biggrin.gif Link to comment Share on other sites More sharing options...
Shez Posted December 11, 2014 Share Posted December 11, 2014 I'd lift the ground (earth) of the projector. I know it is against the rules, but just to chek it out... If the almighty buzz disappears, you got yourself a ground loop. B-)Bearing in mind that in a ground loop, current flows both through the mains earth AND the signal ground, breaking the signal ground will achieve the same effect without silly risks. Link to comment Share on other sites More sharing options...
timsabre Posted December 11, 2014 Share Posted December 11, 2014 I'd lift the ground (earth) of the projector. I know it is against the rules, but just to chek it out... If the almighty buzz disappears, you got yourself a ground loop. B-)Bearing in mind that in a ground loop, current flows both through the mains earth AND the signal ground, breaking the signal ground will achieve the same effect without silly risks. Although on a video system the video will then become noisy/distorted.The audio DI/isolating transformer solution suggested previously is the correct way to fix this problem. Link to comment Share on other sites More sharing options...
Shez Posted December 11, 2014 Share Posted December 11, 2014 Indeed. I was just running with the "test for a ground loop" rather than the final solution. Link to comment Share on other sites More sharing options...
djmatthill Posted December 11, 2014 Author Share Posted December 11, 2014 Some info on future inspection.. Iv never had an issue when iv run the setup using the unbalanced outputs on the mixer so I took the unbalanced rca phono output and fed it into a balancing transformer then Out as a balanced line to the amp.. and it stopped all buzzing and is ok... So a temporary solution for now ... But I always though that balanced outputs were the way forward to stop any problems ...?? Link to comment Share on other sites More sharing options...
alistermorton Posted December 11, 2014 Share Posted December 11, 2014 The output of the mixer might be balanced, but the RCA plugs are unbalanced. That's where your initial "earth loop" problem is. Using the transformers uncouples the ground from the signal path so breaking the loop. Link to comment Share on other sites More sharing options...
MarkPAman Posted December 11, 2014 Share Posted December 11, 2014 I suspect that your balancing transformer is also breaking the path of an earth loop. Link to comment Share on other sites More sharing options...
djmatthill Posted December 11, 2014 Author Share Posted December 11, 2014 Ok then thanks for all ur help on this .. I guess this will work whilst I try and pin point the actual problem then :) Link to comment Share on other sites More sharing options...
pete10uk Posted December 11, 2014 Share Posted December 11, 2014 Ok then thanks for all ur help on this .. I guess this will work whilst I try and pin point the actual problem then :) There is no real problem to pin point. It's just the way it is. An isolating transformer / DI should be in your tool box when ever using unballanced signals, these loops crop up, they can be there then vanish only to reappear for no apparent reason, I've known people looking to fix the cause and got bogged down, £5 box is an easy fix and permanent one. Link to comment Share on other sites More sharing options...
TonyMitchell Posted December 12, 2014 Share Posted December 12, 2014 The output of the mixer might be balanced, but the RCA plugs are unbalanced. That's where your initial "earth loop" problem is. Using the transformers uncouples the ground from the signal path so breaking the loop. If I've understood correctly, the OP is using RCAs from the Denon unit, which is class 2, so the "earth loop problem" wouldn't originate from the sound source. Link to comment Share on other sites More sharing options...
timsabre Posted December 12, 2014 Share Posted December 12, 2014 Might be earthed via the usb through the laptop psu. It'll probably be earthed through the mixer. Link to comment Share on other sites More sharing options...
howartp Posted December 12, 2014 Share Posted December 12, 2014 I'm only reading this thread as we also have a Sanyo projector and happen to have a completely unrelated buzz on the audio, but I wonder if I could ask a question based on a comment above? The output of the mixer might be balanced, but the RCA plugs are unbalanced. That's where your initial "earth loop" problem is. Using the transformers uncouples the ground from the signal path so breaking the loop. Our sound PC is connected to our X32 mixing desk via a 3.5mm > dual RCA cable into the aux 5/6 RCA inputs on the desk. There is a bad hum on the PC's channel, such that when we're not playing audio tracks we tend to mute the channel to remove the buzz... Does this comment imply / suggest / mean that I should be putting a DI/Transformer between the RCA's and the X32 desk in order to eliminate the buzz? Peter Link to comment Share on other sites More sharing options...
david.elsbury Posted December 12, 2014 Share Posted December 12, 2014 Yes, a di or transformer should take care of that for you Link to comment Share on other sites More sharing options...
howartp Posted December 12, 2014 Share Posted December 12, 2014 Yes, a di or transformer should take care of that for you Thanks David! It's annoyed me for three years; I upgraded the onboard sound card to a decent 7-ch PCI card last year presuming/hoping it was the onboard cheap card causing the problem. :( Peter Link to comment Share on other sites More sharing options...
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