Off-hand the only way I can think that your previously 100% cure has dropped to 50% is if another ground loop has accidentally been created.

Have you changed anything in your setup recently?


Martin

--------------------
YewTreeMagic

Hi Martin,
No, it's identical except maybe we plugged the PA / laptop into different power sockets on the wall this time, though I don't think so.

Can I daisy chain my second DI 120 onto the first one to get a "double" ground lift (!) - any other suggetions?

Is it purely a psu issue or would using my external firewire focusrite saffire card help?
Thanks again
Gav

Hi Gav!

If it's purely a PSU issue then unplugging the laptop power supply and running on battery should cure the hum. If it doesn't then something else is to blame. Daisy-chaining DI boxes is pointless, since a ground lift is a ground lift ,and as long as your DI20 is working correctly then it will still be completely breaking the previous ground loop.

Are you sure your new hum isn't due to audio cables lying alongside mains ones, or near to underground mains runs? (try moving them and seeing if the hum changes or goes away).

When you say that you plugged the PA/laptop into different mains sockets this time, do you mean you plugged them both into the same double wall socket, but one in a different part of the room (in which case it would be worth checking that these sockets are properly earthed, using a device like this £4.99 one from Maplin:

www.maplin.co.uk/Search.aspx?criteria=WD53H&DOY=1m11

If you mean that the PA and laptop were plugged into separate mains sockets at different places in the room I'd revert to plugging everything into one socket - this can solve a lot of hum issues.


Martin

--------------------
YewTreeMagic

Really hope someone can help me here. Looks like ive got a similar problem to some others here !

My setup is :

Alesis Active montors -> Edirol SD-90 USB interface -> Compaq laptop.

This setup is giving me 2 problems which I think are both related.

1)When running from the powerpack/mains you hear slight harddrive/laptop internal whirs and hisses which stop when you switch to the battery.

2)When playing back audio from the laptop, via the USB module and into the monitors, every now and then the sound clips/cuts out like its almost skipping a beat. This "beat skippnig" also happens when I plug the mains in/out of the laptop.

I have tried using the monitors to play back output from an ipod/stereo in the same room and they work fine with no cuts/beat skipping or hissing so I assume there is some laptop power issue I need to resolve.

If it helps, this is the USB module I use :
http://www.soundonsound.com/sos/Jul02/articles/edirolsd90.asp

Hope someone can provide me with some advice !

ps - I have used small PC speakers in place of the active monitors and they work fine, as do headphones ?

Welcome to the SOS Forums thehearing!

You've almost certainly got a ground loop because both e laptop PSU and powered monitor speakers are earthed via their mains leads, and then the audio cable between interface and speakers creates the loop.

The cures are described many times earlier in this thread - if your monitors and audio interface provide balanced connections, using a balanced audio cable will break the loop. If not, you'll need to buy a line-level DI box such as Behringer's Ultra DI-20 and connect it between the audio interface and speakers.

Good luck!


Martin

--------------------
YewTreeMagic

Thanks Martin,

Yep - the hum goes if the psu is pulled out and the laptop runs off the batteries. Which is why I bought the DI120 and why it worked. Last time!

Is it possible my DI120 has broken?
I'll try the other one this monday night's practice.
I'll also try your 'all in one socket' approach too.

When the drummer farts, there's a hum aswell. Unfortunately, there is no cure for that,
Gav

Thanks Martin for the quick response!

I'll explore those options and see what happens over the weekend.

Rich

Good luck both!


Martin

--------------------
YewTreeMagic

Hi Martin,
So we had the band practice and the hum's still there, albeit reduced with the DI box ground lift switch on.
We tried a different DI box too.

But then! Just by chance, I lifted the laptop psu up to move it, and voila - the hum went away.
Just like holding a TV ariel in the right place, to get good reception, in the old days if I held the psu up all was fixed.
My producer friend reckoned it was an induction loop from the strip lighting/electrics in the room?
He reckoned that you can buy shielding sheaths for the psu cables that'd help - or maybe a new psu with better shielding?

What do you think sir?
Thanks
Gav

Where can I buy a better quality psu for my laptop?
OR - what about the hum-x:
http://www.ebtechaudio.com/humxdes.html

There's a UK distributer?
Ta
Gav

Sorry Gav, that Hum X product seems to be available for US mains use only, but I don't think you need it.

I suspect the field from the laptop PSU transformer was being picked up either by your audio interface or a nearby audio cable. You shouldn't need to replace the PSU - just keep all wall-warts and line-lumps it as far away from all audio devices as you can manage, and if any audio cables do need to pass close to any carrying mains voltages, don't let them run in parallel - arrange them so they cross at right angles.

I also seem to remember Max recommending that some of his clients fit such problematic wall-wart PSUs inside an earthed steel box to reduce any interference they push out, although I've never had to resort to this myself.


Martin

--------------------
YewTreeMagic

Hi Martin,

I tried holding the psu in all sorts of interesting positions, but the hum/buzz never went away fully.

As I'll be playing in different venues for gigs I really need to have a fool proof solution.
I don't mind paying the money for a different psu type, if that'll fix it?
What ones are wire up correctly?

Please help!
Gav

Most laptop PSUs output DC, so I suppose it's possible that yours still has plenty of ripple on its supposedly DC output and you could cure such a problem with a replacement PSU of some sort. I've just had a look at my laptop's PSU, and it outputs 19 volts DC at 3.16 amps, with the positive connection on the 'inner' part of the plug. If you want to try another PSU for yours you'll have to note down this information from yours and try to find one that offers the same voltage and current capability.

However, I'm at a bit of loss here, since you no longer have a ground loop, the hum definitely disappears as soon as you pull the PSU and switch to battery power, yet it varies when you move the PSU around, which suggests an induced (rather than fundamental design) problem. In other words, power supply ripple won't change an iota if you change the position of the PSU, and until recently you didn't have this hum at all. It's possible the PSU has developed a fault and is radiating more interference which in turn is being picked up by your audio cables or interface, but I still suspect that changing it won't cure your problem.

Let's just double check before we go any further - do you still hear this hum on headphones plugged into your audio interface when you unplug the audio cable between this interface and the DI box?

If the hum disappears then it's definitely some sort of ground loop, or possibly a fault with your new DI box (unlikely, but to check this try to borrow another DI box).

If the hum remains then the problem could be PSU-related (although I still don't see how anything has changed since the DI box affected a complete cure), or an induced problem from nearby mains wiring (which still sounds more likely to me - to check for the latter try setting up exactly the same set of gear in another room, and if the problem then disappears it's some sort of an induced problem.

I'll also see if I can point Hugh at this thread for another opinion.

Hang in there!


Martin

--------------------
YewTreeMagic

Hi Martin,

I'll try using headphones at the next practice.
I've tried 3 DI boxes, and they all partially reduce the hum - by about 60%. This is through the PA desk.
At one practice, we didn't have the PA and so I went through a wee guitar amp, and the ground lift worked 100%.

Thanks for your help so far.
Gav

Hi Gav!

I had a discussion with Hugh, and the only other things he could think of were whether your DI box was touching some other metal object, or possibly that you'd accidentally swapped over some earthed mains lead with a non-earthed one.

I think we're both stumped otherwise!


Martin

--------------------
YewTreeMagic

Hi again,

So, if it's not a ground loop issue, but something else that the charger's picking up (as I said previously, my friend reckoned it was the overhead strip lighting) - what shielding or alternative psu can I buy.
There must me fancier posh psu's for musicians that are immune to all these problems?

Thanks!
Gav

Just thought I'd add my experience here, I was using a Toshiba Tecra with the standard three prong psu and I was getting buzzing from both an Echo Indigo io and the onboard soundcard. I tried using a smaller two prong Toshiba psu that my dad bought for his Tecra when travelling and the buzzing has disappeared

Only thing is the old psu was rated at 15v 5A and the new one is 15v 3A. Is this anything to be concerned about? My dad's been using it with no problems for the past 18 months or so.

Quote Kayvon:

---

Just thought I'd add my experience here, I was using a Toshiba Tecra with the standard three prong psu and I was getting buzzing from both an Echo Indigo io and the onboard soundcard. I tried using a smaller two prong Toshiba psu that my dad bought for his Tecra when travelling and the buzzing has disappeared

---

Aye K ...

Dell with their recent 2 prongs on their d series lappy psu's have managed this too.

There are "generic" 2 prong power adaptors available for some laptops.

Quote:

---

the old psu was rated at 15v 5A and the new one is 15v 3A. Is this anything to be concerned about

---

What does the laptop say on the base as to amperage.

Quote table for two:

---

Quote:

---

the old psu was rated at 15v 5A and the new one is 15v 3A. Is this anything to be concerned about

---

What does the laptop say on the base as to amperage.

---

I should've checked that before shouldn't I? It says 15v 5A. Methinks I need to learn some basic electrical theory.

hey

right... i want to try and get rid of the buzzing in my monitors using a DI box. i have 2 monitors connected to my interface in separate line output ports with 1/4 jack to jack cables. so does this mean i need 2 DI boxes (one for each path)?

Yes. However, don't feel too hard done by, since most people are in the same position as you. You don't necessarily need two DI boxes though, since there are now plenty of stereo ones with two inputs and outputs, such as the ART Cleanbox II ( around £28 from www.artproaudio.com ).

You many not need a DI box at all if your monitors provide balanced inputs, because in this case you can make up balanced cables (if your audio interface provides balanced outputs and your monitors have balanced inputs) or pseudo-balanced cables (if your audio interface only provides unbalanced outputs yet your monitors have balanced inputs).

Details of wiring for pseudo-balanced cables is described earlier in this thread.


Martin

--------------------
YewTreeMagic

Thanks goodness I found this thread!

I am having what I think might be a ground loop problem. I have been using a Toshiba Satellite connected directly to my Samson amp via a mini jack to stereo cable. This has been giving me no problems at all.

However, I recently got a new laptop - a Sony Vaio. When I plug the mini jack into the Sony Vaio sound out, it emits a buzzing, interference type sound from the amp speakers. This sound changes when the laptop hard drive is doing something, or when I even move the mouse cursor on the screen.

The laptop and samson amp both run into the same mains power socket by way of a 4 way extension lead. So I guess they must be running from the same ground? The weird thing is, I decided to remove the Earth from the extension lead, thinking at least that that would stop the ground loop, however, the buzzing noise remained??

When I listen to sound from headphones from the Vaio it is fine. And when I play music from the built-in laptoo speakers it is fine. Its just when I plug the minijack from the laptop to the amp that i get the awful buzzing.

I'm kinda worried I wont get rid of this problem and I'll be stuck with an unusable laptop - their reluctant to swap it for something else at the shop and say i need to trouble shoot via Sony.

Is it possible to get a ground loop problem when both devices are not connected to Earth?

Any ideas what I can do to fix this? Thanks a lot for any assistance!

All the best,
Dav

Welcome to the SOS Forums dr_sos!

Please don't remove the mains safety earth from your extension lead, as it could result in your death.

Your post suggests a classic ground loop problem, with a classic solution.


1. If your interface provides balanced outputs and what you're connecting it to has balanced inputs then balanced rather than unbalanced cables should cure the problem.

2. If the audio interface provides unbalanced outputs and what you're connecting it to has balanced inputs then you can make up pseudo-balanced cables to cure the problem (wiring details in that thread).

3. Only if you're connecting to unbalanced inputs will you need a DI box. The cheap and cheerful isolation solution is a ground loop isolator (from about £4) sold for in-car use, although you may compromise audio performance with high frequency loss and low frequency distortion with higher audio levels. The recommended approach is to buy a quality DI (Direct Injection) box such as the ART Cleanbox II (around £28 from www.artproaudio.com) or the MTR DI-2P Passive 2-channel DI Box (about £48 from www.mtraudio.com).

Removing the earth from your 4-way extension lead hasn't broken the loop, since both devices are still plugged into it - their earths are still connected both via the extension lead and via the audio cables between them, thus creating a loop.


Martin

--------------------
YewTreeMagic

Sorry to keep going on about this, but could someone please give me a link to buy a properly earthed 3pin charger for my ACER Aspire 5504 laptop.

I've emailed redsub and other PC audio specialists - but they only sell chargers for their laptops. All other web searches simply find links to the charger I already have!

There must be one out there that I can use?
PLEASE help. I am truly desparate.

Gav

Dear me, this ground loop business seems to be a bit of a minefield.

I have ground loop issues with my existing laptop (rather a cheap model). I'm thinking of upgrading the laptop. Question - are Macbooks designed in such a way that ground loops will not be a problem (i.e. through better internal shielding, PSU design or whatever)? I plan to use the laptop connected to a Line6 UX8 (which will be plugged in to the mains) connected to some monitor speakers (which will be plugged into the mains). I'd like to be able to shell out for this stuff and know that I won't be trying to eradicate hum when it arrives...!

If anyone can advise, I'd be grateful.

--------------------
Alex

I'm afraid i'm the latest victim of these ground loops. Just to check if i'm doing the right thing :

I have a digidesign MBOX 2 pro, connected via 6*-4 pin firewire to my Sony vaio laptop. The laptop has an earthed power connection. The monitor outs (TRS balanced) from the Mbox go to the TRS balanced ins of my SMpro audio IN5 mixer (that I use as a monitor controller, and where my live rig is also hooked up to) using a TRS 8-way snake from Thomann. From the IN5, a XLR-XLR cable goes to each of the KRK monitors. So in theory, the signal path should be fully balanced.

But i'm hearing the classic noises when the laptop is plugged into power. As soon as I disconnect the power, it is gone.

I don't hear any noises on the headphone output of the mbox2pro, but they do appear on the headphone output of the IN5, so the ground loop must be between the IN5 and the MBOX2, not between the monitors and the IN5 (which I knew since I didn't have it before).

Since i'm allready using balanced cables, what could be the source of the ground loop? Are the IN5 inputs not balanced, allthough the manual says they are? Would cutting the shield in the balanced cables do it?

Any input would be greatly appreciated.


P.S. : is it me, or do sony vaio laptops appear way too much here?

--------------------
"Do not fear mistakes. There are none."
Miles Davis

Yes, you ought to be OK with balanced cables throughout, but life's not always totally accommodating

The problem might be that one of your gear items is not internally grounded properly, and cutting the shield at one end of the balanced cables might help (preferably at the receiving end).

The classic reference wth lots of details is here: www.rane.com/note110.html

And as for Sony Vaio laptops dominating this thread, I suspect Dell would come out on top in that contest


Martin

--------------------
YewTreeMagic

Wonder if folks can help me - simple system just set up.
Acer 6492 laptop, USB audio interface Alesis IO2, Edirol speakers.

Just started playing some notes on virtual instruments in Cubase LE4 - Halion and Arturia Factory SE.

I don't get a hum but after releasing a note I get a "ffffffT" sound. ie a kind of hiss for a second or 2 then a click, then the hiss is gone.

It does this in both instruments.

Adjusted latency all kinds of ways but it did nothing.

Turning up main level on audio interface and reducing level of speakers reduces the sound - doing the opposite - audio interface low, speakers hi - makes the sound much louder - so I guess that's it?

Any thoughts?

cheers

Christo

Edited by unclechristo (18/04/08 01:16 AM)

Welcome to the SOS Forums Christo!

If this sound disappears altogether a couple of seconds after you release a note, I doubt that it's a ground loop problem, since the noises resulting from this tend to be there all the time (although they do tend to vary with hard drive, mouse, or graphics activity).


Martin

--------------------
YewTreeMagic

Hello everyone,

I also have a problem whereby I have a hum that goes away when you unplug the adpater from the laptop (Amilo pi 1536) or touch strings on a guitar or the metal work on Rig Kontrol 2.

Similarly to the previous poster I also only have Laptop, Soundcard (X Station or RK2), Guitar and Headphones.

Martin, If I used a Universal AC Adapter (with a metal earth pin) do you think this would resolve the issue? I've struggle to find one that states compatibility with the Amilo pi 1536 - would a universal one with 20v 4.5a be suitable even if it's not listed on the suppliers web page?

You mentioned earlier a Earth wire attached to the earth pin of a 3 pin plug and connected to the laptop - is this 100% safe for the laptop?

Best regards, Paul

Welcome to the SOS Forums Paul!

A laptop mains adaptor with figure-of-eight mains cable (i.e. two core) should be double-insulated so that any exposed metalwork on the laptop can't come into contact with either of the mains wires.

If this is the case then you can safely earth the laptop elsewhere - after all, this is exactly what will happen if you connect one of its ports to another mains-earthed device, such as a desktop PC, or if you plug an audio interface into your laptop and then plug its outputs into a mains-earthed amplifier or active speaker.


Martin

--------------------
YewTreeMagic

I connected the DV Socket of my DVD Recorder to the Firewire connector of the laptop and the noise went away.

Thanks.

I'm glad you're sorted

Next!


Martin

--------------------
YewTreeMagic

Excellent stuff! I know a lot of people who get this problem.

No one's mentioned filters, so just wondering what everyone's views on these are.

As I wrote here , I've successfully used surge protectors with noise filtering in the past. I don't know the technical ins and outs of how it works, but it seems to do the trick.

Any thoughts, Martin? Would be good to get your point of view and experiences on these.

Alex

--------------------
Audio Support - Experts in Music Technology
The very best in music technology tuition and support for musicians, producers and schools

Hi Alex!

Well, mains filters are designed to filter out RF interference that's already on the mains supply, as well as deal with mains spikes.

I've got one of those Belkin distribution boards with such filtering built in, and it ensures that my mains signal is relatively pure, as wll as providing some protection for the gear connected to it in the event of lightning strikes and suchlike.

However, ground loop problems are an entirely separate issue that can't be solved by RF filtering and spike protection - to do this you must break the loop, which generally means a DI box with transformer-coupling so there's no direct connection between one audio item and the next.


Martin

--------------------
YewTreeMagic

Yes, another laptop noise issue here!
I am running an Acer Travelmate laptop using a Mackie d4.Pro mixer with built in Firewire audio interface.
Typical ground loop style noises, when moving graphics / windows stuff etc. Beautifully silent when running off battery power.
So far so typical.

However, the noises are audible via the mixer headphone socket as well as at my Alesis powered monitors (i.e. the connection between mixer and monitors is fully balanced).

Am I right in thinking something like the Cleanbox II is not going to help. If i put it between my main outs and monitors it's not going to get rid of the noises as they exist before this point? Is that the right way of thinking? i.e. the noises are still there in the headphones when nothing else is connected to the mixer and I am streaming audio via the Firewire interface into the mixer.

As essentially the Firewire interface could be thought to be separate from the mixer and just intimately joined and this is where the A/D/A conversion happens and the signal is joined with the otherwise analog mixer. So i need to break the loop there - but that seems practically impossible.

Am I totally wrong? Anything else I can do to test? Don't seem to have the same noises when using headphones direct on the in-built soundcard on my laptop, but the output is a bit feeble so hard to tell.

Thanks

--------------------
http://www.skratchworx.com

Just follow this step-by-step guide I wrote for SOS July 2005 and see when the noises stop. Then you'll know whether or not a DI box will help:

www.soundonsound.com/sos/jul05/articles/qa0705_1.htm

In your case I suspect the problem may be because both your laptop and Firewire mixer are earthed, and the ground loop is created when you connect the Firewire cable between the two. This is a tricky one to solve (although several people here have cannibalised their Firewire cables to remove the earth connection).

Good luck!


Martin

--------------------
YewTreeMagic

Yep it appears the noises materialise the moment the firewire cable touches each piece of equipment (i.e. even at the edges of the socket so it isn't inserted fully).
I've tried another firewire cable hoping it may be a one off, but still the noises.
I take it there is no easy way to solve this? I may drop Mackie support a line and see what they think.

--------------------
http://www.skratchworx.com

Hi there.

As I'm going to try work out my ground loop problem (another one ) using DI boxes I have one quick question:

Is there any chance to break the loop inside USB cable??

Thanks

--------------------
www.myspace.com/biczmusic