Distorted Sound?

[BriMac 0]

I have had this problem for quite some time now, every time i do a gig i always have a this distorted fuzzing sound coming out my speakers, I thought it may be a dodgy audio lead or the amps been to close to the speakers and mixer i just didn't know where to start.

 

I did find out the other night what was causing the problem when i got talking to dj at the bar i found out that it was the power adapter for the laptop due to the earth so when i unplugged it from the laptop the distorted sound had stopped 'happy days' the guy says to cut the earth out for the adapter but i don't think i should.

 

so is the any other way round this? would a usb sound card do the trick or an audio interface?

been looking at a Behringer U-CONTROL UCA202? but don't what i should

 

regards

brian

[fester 0]

I've come across this argument so many times now. Ground loop hum caused by laptop PSU, to cut the earth or not to cut?

 

To be honest in nearly every case it's perfectly fine and safe to cut the earth out of the 3 pin plug. The "earth" on a laptop PSU isn't even used as an earth for traditional safety reasons. It's there to make it conform to RFI (Radio Frequency Interference) regs and is used for filtering away RFI, rather than for any safety reasons.

 

There really isn't much to be concerned about, the PSU is plastic cased, it's isolated from the output via a commutating transformer which makes it a class 2 item. Safety is in no way compromised and it will pass a PAT test.

 

Cut the wire.

 

Or buy an overpriced 2 wire PSU (one that has no earth wire in the first place).

 

 

Can't edit for some reason, so had to post again

 

would a usb sound card do the trick or an audio interface?

been looking at a Behringer U-CONTROL UCA202? but don't what i should

 

No, the laptop PSU will still continue to introduce noise no matter what you put in there. Adding more devices into your signal chain will not remove the hum, if anything you are simply adding more potential problems.

 

The only other thing you can do if you really don't fancy cutting the earth is try adding a Ground Loop Isolator.

 

[Celebration Discos & Karaoke 0]

I have had this problem for quite some time now, every time i do a gig i always have a this distorted fuzzing sound coming out my speakers, I thought it may be a dodgy audio lead or the amps been to close to the speakers and mixer i just didn't know where to start.

 

I did find out the other night what was causing the problem when i got talking to dj at the bar i found out that it was the power adapter for the laptop due to the earth so when i unplugged it from the laptop the distorted sound had stopped 'happy days' the guy says to cut the earth out for the adapter but i don't think i should.

 

so is the any other way round this? would a usb sound card do the trick or an audio interface?

been looking at a Behringer U-CONTROL UCA202? but don't what i should

 

regards

brian

 

I wouldn't advise removing the earth from anything. It is there for a reason. It will also void your insurance if anything ever happens.

 

The way i have gotten around this is to use an in-line filter between your mixer and your laptop audio lead. They are only a few quid off ebay. See the link below -

 

http://www.ebay.co.uk/itm/3-5mm-Earphone-J...=item41560179c6

 

This is what i have and it works 100%.

 

Hope this helps.

[Derek Paul 0]

I had the same problem with my notebooks, and like BriMac I did not want to cut the earth plug out. As an experiment I did take a 1 foot extension cable without an earth plug and used that to connect the notebook. Just as Fester said “problem solved and no issues without earth to the notebook”.

 

However I still did not like the idea of removing an earth connection that the manufacture has installed. So I solved the problem in two different ways. For my back-up notebook I use an Ebtech Hum-X. I am in the USA and have been unable to find an equivalent product for 240v systems in the UK.

 

For my main notebook I used 2 Behringer MICROHD Hum Destroyer HD400. They are expensive at about £26 each, but it really did the job. And remember you need one for each stereo channel (i.e. if you use the headphone output you only need one, however if you use a midi controller with a soundcard sending 2 channels to the mixer, you need two).

 

I have tried a Radio Shack product similar to the Skytronic Ground Loop Isolator. I have a few of these and after time everyone developed a fault on one or other channel.

 

You can find both the Behringer and Skytronic products on Amazon.

 

[McCardle 1]

Leaving aside the ever emotive subject and well worn topic of safety and insurance and getting down to the nuts and bolts, I would examine why a manufacturer has included a 3 core cable when a 2 core would do, I would also question why a SMPSU unit has an earth pin when its in a plastic box with no exposed parts .

 

Believe me, manufacturers, especially Chinese and HK ones (where most PSU's and laptops originate) do not go to the trouble and expense to put 3 core cables on appliances unless they have to or the design engineer has dictated it. After all copper prices have been at record highs this year, and 2 core cables, are much cheaper than 3 core, especially when you are bulk buying several miles of it a week.

 

These mass production companies out in the far east don't go spending money unless they have to, nor do they go a bundle on incorporating many internal safety features or a decent level of electrical isolation. Often it has the bare minimum of protection, which is generally all centered around the protective earth. All they want is a working PSU to sell to the laptop manufacturer across the industrial estate for a few $

 

So on some complex SMPSU designs, the Earth can have a practical function rather than just preventing electrocution!. For example....

 

Some SMPSU are designed so that the Earth is connected to some internal metal / screened parts via a large value resistor this stops the secondary side from 'floating'.

 

Equally, it can also serve as a ground connection to a delta style capacitor, this is a 3 terminal capacitor on the primary side of the power supply which helps prevent RF interference from the switching design. By disconnecting the earth from this cap and leaving its terminal unconnected, you could actually solve one hum problem, but create another, and get a crackling caused by the lack of the Delta Cap, creating noise similar to that of a light switch being turned on / off....hundreds of times per second

 

Finally some and over voltage protection components may require the earth to be connected in order to operate properly, you wouldn't be aware of this until the PSU or its internal isolation broke down, or the tab on the main switch mode mos-fet went S/C and reached the same potential of the rectified mains voltage feeding it, without an earth, the first you would know about this, would be when 300v DC was fed to your laptop through the screen on its low voltage cord, which believe me, won't do it or you much good but I believe its far more expensive than pyrotechnics

 

Remember that an earth wire isn't just a means of protection against electrocution to you, it can also serve as protection against failures in other parts of the circuit, such as parts becoming live inside the case which shouldn't be live, and indicate that some component or internal isolation has broken down or is about to break down, resulting in a metal heatsink or screen becoming live inside in the case.

 

Whilst this happening inside the case isn't in itself an electrocution risk, in this scenario a correctly connected earth to the metal part / screen / heatsink would force the mains fuse to blow indicating "Hey Houston we have a problem" and your laptop would more than likely live to work another day (at least once you have spent £10 on a replacement psu)

 

PSU's are made cheaply, often at the expense of internal fuses and decent thermal protection. I've witnessed many SMPSU based mobile phone chargers where the only protection is the 32A RCD protecting the ring main into which it is plugged, and in a 'fight' guess which one would win :scared:

 

Believe me, the Earth connection may be the only protection that the design has, (or at least form a big part of it operating ) you really don't want to go disconnecting it.

 

Or you can forego all of these early warning signs, disconnect the earth, and let your laptop failing in front of you, alert you to its PSU's demise.

 

Your choice - choose wisely

Edited November 15, 2012 by McCardle

[BriMac 0]

I wouldn't advise removing the earth from anything. It is there for a reason. It will also void your insurance if anything ever happens.

 

The way i have gotten around this is to use an in-line filter between your mixer and your laptop audio lead. They are only a few quid off ebay. See the link below -

 

http://www.ebay.co.uk/itm/3-5mm-Earphone-J...=item41560179c6

 

This is what i have and it works 100%.

 

Hope this helps.

 

this seems like the best option but how ever i have now taking the earth out plug, i did have a word with my friend whos an electrician and he says it will be fine so am trusting him but how ever i will order one of these off ebay just to be on the safe side :yes: