Well that's handy - I can answer Deft and Marcin together in a single post

You can try modifying the USB/Firewire cable by cutting through its outer plastic sheath near the plug at one end and carefully severing the screen connection - this has successfully broken the ground loop and got rid of the nasty background digital noises for some people.


Martin

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

Thank you Martin.

I shall fight with my USB.
If I may...

I need 4 DI boxes, so I thought maybe I get one rackmount.

Is there anything against
RACKMOUNT DI BOX 4CH PASSIVE

http://www.studiospares.com/pd_450840_RACKMOUNT%20DI%20BOX%204CH%20%20%20% 20PASSIVE%20DI%20BOX.htm

What about sound quality??

Any advice will be appreciated

Regards

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

Hi Martin. Thanks for the tip.

I think I have found a solution anyway, which is a bit of a fudge but seems to have worked.

My Mackie d4.Pro mixer has a universal internal power supply that accepts 100-240V with standard IEC socket.
I have now used the US cable that came with it and plugged this into my power strip via a step down transformer. So my UK supply is stepped down to 120V and the Mackie seems happy with that and the noises are gone (presumably because the UK side of the transformer fitting has a plastic prong for earth?)
Does this seem particularly stupid or dangerous? I'm assuming this is o.k. (surely I wouldn't be able to buy something in a shop that was dangerous....erm....)

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http://www.skratchworx.com

Quote Deft:

---

Does this seem particularly stupid or dangerous? I'm assuming this is o.k. (surely I wouldn't be able to buy something in a shop that was dangerous....erm....)

---

By using the two-core US mains cable the metalwork of your mixer is no longer connected to the mains safety earth. Yes, this cures ground loop problems, but in the event of a fault this metal work might become 'live' and be dangerous, or you'll be relying on the earth connection via whatever other gear is connected to the mixer, and might blow that up instead of yourself.

That's why we have a solid earth connection in the UK for safety reasons.


Martin

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

Yeah I got a bit anxious after about an hour of using the transformer, so went back to my noisy (and hopefully more safe) setup.
Seems odd that the transformer allows connection of the US grounded style plugs yet doesn't have the ground connected the other end?
Anyway I have purchased a few Firewire cables to try my butchering skills on.....

Let us know how you get on - it's good to amass some practical solutions that work without having to buy extra hardware!


Martin

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

Cutting the screen around the 4 conductor cores in my Firewire cable doesn't appear to be a workable solution (after a few different attempts).

Yes it definitely removes the noises, but it appears the Firewire connection needs the screen in some way for communication.
So the interface doesn't communicate properly with the laptop if the screen is disconnected (I couldn't find much info on that on the web).
You can get tasks working (like streaming audio) and then disconnect the screen and it keeps going o.k. But then next time you re-initiate communication it will stall.

So it looks like I have run out of options for my ground loop noises.


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

Hi guys.

Since DI box is one of many solution for ground loop I have a question about connecting DI box.

I feed signal from the sub bus of my mixer to line in on my interface.
To get rid of ground loop I connected DI box between.
Is it better to go from DI box to line in or maybe to mic in - as the connection XLR-XLR would be very easy.

What's your opinion?

Regards

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

It depends on the DI box you're using - some are designed for line-level inputs and have a line-level output, and should therefore be plugged into (one guess!) a line in.

Others are designed to increase input impedance and at the same time drop the output level, so you can send a line-level signal into them but plug their output into a balanced mic input.

However, if you have a balanced line-level input then you can normally make up a pseudo-balanced cable and do away with the DI box.


Martin

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

Thank you Martin for very quick answer.

I'm going to check pseudo balanced connection, but I'd like to be sure about DI box as well, so...

I tried to find spec for my DI box (MTR DI-2P, passive) but no luck.

The only thing I know is impedance of it's ins and outs

in - 47kOhm
out - 600Ohm


My interface's (Tascam US-122) ins are:
mic balanced - 2.2kOhm
line balanced - 22kOhm

What's the better connection then?

Regarding levels I found that I have "level attenuation" on the DI box (0dB,-20dB,-40dB) - that's all.

What's the way to follow??

Thank you.

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

I'd plug it into the line-level input, but if that's balanced then you probably don't need a DI box at all - I've always made up pseudo-balanced cables to connect my keyboards to balanced line-level inputs on analogue mixers.


Martin

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

My new Dell Precision M6300 is causing me no end of problems in terms of audio interference, when using the PSU. WHen plugged into any other piece of equipment (even an amplifier) it makes a terrible noise. This disappears completely when disconnecting the PSU and running the laptop on battery power, or in the case of my KRK monitors when activating the ground lift switch.

The problem is, I need to use my laptop in a live situation. I recently purchased an ART DTI Dual DI box. This *greatly* reduced the level of the unwanted noise, but unfortunately *didn't* get rid of it completely. There is still a faint whine and chirping noise present in the audio signal

Whilst this might now be much of a problem when listening at home, I'm going to be using this laptop as the centre of my live rig, and will be performing at festivals on some pretty big sound systems, which will make the background noise much more noticable

At the moment the best solution i can think of is to run the laptop on battery power for the duration of the set. It *should* have enough juice to run for 90 inutes without the PSU but as I'm sure you can appreciate, this is hardly an ideal situation

Do any of you have any other suggestions? This is driving me crazy!

Much appreciated

Just to add my twopenneth here - for people looking to buy new laptops but worried about audio interference - get a Macbook. It's good reliable hardware, and even if you're a Windows user, you can now run Windows natively on a Mac - and it performs very well for audio.

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

Quote Mudchild:

---

Just to add my twopenneth here - for people looking to buy new laptops but worried about audio interference - get a Macbook. It's good reliable hardware, and even if you're a Windows user, you can now run Windows natively on a Mac - and it performs very well for audio.

---

I have to agree if anybody's looping for a new laptop get one which doesn't have the ground connected. You can tell by looking at the charger. It will have the square in square symbol on it and also have a 2 pin fig 8 cable / socket. If a macbook is above budget have a look at the samsung range of laptops. Most of the ones that are 14" and below come with 2 pin chargers. I'm currently using a samsing x10plus which can be picked up second hand for under £200. Some other models off the top of my head are q35, q45, r20.

Edited by Plexman (21/06/08 09:21 AM)

Yes my music partner just got a macbook and it seems to work very well. I'm thinking I should have spent a bit more and opted for a Macbook Pro now, but it's too late

Are there any other solutions? I'll buy a new PSU if necessary...

Quote Domsmart:

---

I recently purchased an ART DTI Dual DI box. This *greatly* reduced the level of the unwanted noise, but unfortunately *didn't* get rid of it completely. There is still a faint whine and chirping noise present in the audio signal

Whilst this might now be much of a problem when listening at home, I'm going to be using this laptop as the centre of my live rig, and will be performing at festivals on some pretty big sound systems, which will make the background noise much more noticable

---

Are you sure you haven't still got another ground loop? Remember that any two mains-connected devices connected via a screened audio cable will create such a loop. Check also that the laptop PSU isn't inducing noises by being in proximiity to audio cables.


Martin

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

Positive. The laptop is connected to the interface (novation NIO) via USB, and the interface is bus powered. With no other equipment connected and the interface connected to the amp (or whatever) via the DI box, there is still interference, however as I mentioned the level of this is MUCH lower than without the DI box, and seems to be mostly HF. As before, it disappears completely if I disconnect the PSU and run the laptop on battery power.

I contacted Dell and they told me that they'd need to replace the laptop's motherboard, however I'm doubtful about this and in any case I've got some big gigs coming up in a matter of weeks and can't be without my machine...

I guess I'll just have to live with it for the moment

I'm afraid Dell laptops (and in particular the Latitude-D and Inspiron ranges) have caused lots of problems over the years for musicians. See here for instance:

www.soundonsound.com/forum/showflat.php?Cat=&Number=318

Hmm... In that case it does suggest a problem with the Dell PSU perhaps injecting noise into your laptop. Like you I'm aso doubtful that replacing the motherboard would help - unless there's some sort of PSU stabilisation/smoothing circuitry on there that they have improved since you bought this model.

Some laptops allow you to fit two batteries for longer life - is this an option on your model that would give you greater confidence live?


Martin

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

Hi,

I am no stranger to ground loops on my Dell laptop with 3 pin PSU, I cured it with a Behringer DI as outputs were just going to active monitors, which worked fine but now......

I've now started doing live recordings at gigs and am running mic's through my Firestudio interface, then out to a mixer, I've got a ground loop on the whole connection, on all 8 channels.

The 8 outs on the interface are balanced and the line inputs on the mixer unbalanced, so am I right in thinking if I buy a balanced 8 way loom, then replace one end with unbalanced jacks, it will solve the problem?

Unfortunately not - if the mixer offered balanced inputs everything would be fine (use balanced cables throughout), and if your interface had unbalanced outputs but the mixer offered balanced ins you could use pseudo-balanced cables to avoid ground loops.

However, if you connect balanced cables from balanced outs to unbalanced ins you lose the balanced nature of the connection.


Martin

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

The desk has XLR in's too,

could I use a TS to XLR or TRS to XLR to solve the ground loop? the only other thing I can think is more DI boxes?

You'll need balanced line-level inputs to do the job properly. If those XLR inputs are mic inputs then you probably won't be able to turn the gain down sufficiently to run line-level signals from your interface without running into clipping. You might get away with it if you built in attenuators into the XLR end of each cable to drop signal levels right down, but it's still not an ideal solution.

If you do have balanced line-level inputs then TS to XLR cables would work if you wired them as pseudo-balanced, while TRS to XLR would be the perfect and easiest solution.

Otherwise more DI boxes is indeed the best solution


Martin

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

Hi there. I had a ground loop problem on my old rig
Sony Vaio TGN duocore 2gb ram XP PRo SP2 running traktor 3.3
EKS XP10 midi controllers (with soundcards)
Ecler SMAC 70i Mixer
Mackie SRM 450s
I solved it with a RCA ground loop isolator.

I have now changed my set up
same laptop
Mackie d4 pro mixer (with firewire soundcard)
Allen & Heath Xone 1d midi controller
same 450s.
Now I have nowhere to put the ground loop isolator and the hum is there with laptop power supply on. There has been mention of swapping the 3 pin Sony power lead for a 2 pin one. Is this reasonably safe can I ask?
I also know of another Mackie d4 pro user who disconnected the shield on his firewire cable. No hum but the cable didnt work properly or at all afterwards.
Any thoughts anyone would be gratefully appreciated.
Cheers Rob

Quote Deft:

---

Cutting the screen around the 4 conductor cores in my Firewire cable doesn't appear to be a workable solution (after a few different attempts).

Yes it definitely removes the noises, but it appears the Firewire connection needs the screen in some way for communication.
So the interface doesn't communicate properly with the laptop if the screen is disconnected (I couldn't find much info on that on the web).
You can get tasks working (like streaming audio) and then disconnect the screen and it keeps going o.k. But then next time you re-initiate communication it will stall.

So it looks like I have run out of options for my ground loop noises.

---

I have the d4 pro also with same issue Deft. Did you get any joy from Mackie Tech Support?

Quote RobHirst:

---

I have the d4 pro also with same issue Deft. Did you get any joy from Mackie Tech Support?

---

Nothing sensible, we went around the issue on a couple of exchanges and eventually he just said to buy a mains power conditioner. It is still really annoying. I'm probably going to get a desktop at some point in the near future and hopefully it won't have the same problem.
Finding a safe alternative 2-pronged power supply may be a good option, assuming such a thing exists (some laptop power supplies must be like this?)

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

Finding a safe alternative 2-pronged power supply may be a good option, assuming such a thing exists (some laptop power supplies must be like this?)

---

I will have a look too. What is really bugging me is that I had an old model d2 with f/w and it worked perfectly with the same Sony Laptop. I just sold it cos I wanted a scratch certified mixer with 4 channels. If it works etc etc !!!!

Hi Deft. Good news which I hope will help you too. I got a 120w Taurus Universal Power Supply off ebay for £24. It looks pretty solid spec. It had a figure 8 cable going out to usual 3 pin wall socket plug. Lo and behold Silence is golden!!!!! So it was clearly an issue with my Sony Vaio power supply. If it worked with mine may be a good chance it will sort your problem as well.
Best Rob

Quote RobHirst:

---

Hi Deft. Good news which I hope will help you too. I got a 120w Taurus Universal Power Supply off ebay for £24. It looks pretty solid spec. It had a figure 8 cable going out to usual 3 pin wall socket plug. Lo and behold Silence is golden!!!!! So it was clearly an issue with my Sony Vaio power supply. If it worked with mine may be a good chance it will sort your problem as well.
Best Rob

---

Cheers Rob - I think I will chase this solution too, as I have just got a 22" TFT hooked up to my laptop which has visual ground loop interference too! Double annoying.
I have found a universal supply at Maplin which looks like it doesn't use a 3-prong safety earth fitting*, so should probably do the trick.

*Edited to say, yes - it is a double-insulated variety not some cowboy adaptor fitting (i.e. has the double sqaure logo)! Actually I don't know why I didn't just buy one of these sooner......

Edited by Deft (22/08/08 05:34 PM)

This sounds good - universal PSU's with figure-of-eight cable will certainly cure many laptop ground loop problems without removing a vital mains earth connection (as they will be double insulated, you don't need one)

This Taurus one looks well built too (although it does have a built-in cooling fan). Here's a link with some spec details:

http://cgi.ebay.co.uk/120W-Universal-AC-Power-Supply-+USB-Laptop-iPod-Mobi le!_W0QQitemZ310076580631QQcmdZViewItemQQimsxZ20080820?IMSfp=TL0808201928r19667


Martin

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

Just wanted to finish off the saga by saying that as expected, my new double insulated laptop supply cured the ground loop issues evident from my attached Firewire mixer and TFT monitor.
So nice to not see / hear the loop!
I got a "Trust" generic adaptor. Not too bad but the actual adaptor doesn't fit amazingly snugly in the laptop socket, so probably not great for those who move around a lot.

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

Now this seems very interesting!
I also have a sony vaio laptop with hum problems. They dissapear as soon as the laptop is running on batteries. The standard power supply that comes with it has an earth connection (i'm in belgium, so different plugs here), but am I right that you guys are saying I could get one that is as safe but without the earth connection (just a two pin lead)?

My system never hummed untill I introduced the laptop and the mbox2 pro. The mbox isn't causing this hum, I also have this when connecting the standard audio out to my mixer. All my connections are fully balanced between the mbox pro and the sm pro audio IN5 that serves as mixer and monitor controller. but no luck yet.

P.S. : would it be interesting to know that my old desktop computer with an unbalanced connection from the internal m-audio 2496 soundcard to the M-audio In5 never had any ground loop issues? Both the new and old computer are plugged into the same socket.

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

Edited by Dunewar (07/09/08 07:43 AM)

Hi Martin.

I am yet another Sony Vaio user (a VGN model) plagued with noises when using a USB song card or Firewire connection (although only when the PC is connected via its normal earthed psu - it works fine with batteries). Isolating the computer using the ART Cleanbox II didn't help much so I am seriously thinking of trying out your suggestion of using a double-insulated psu which isolates the PC from the mains (SOS December 2008).

Rob Hirst mentioned, in August last, use of the Taurus psu for a similar Sony notebook, but I note that this unit does not produce exactly the correct voltage - the Sony notebooks require 19.5v, not the 19v or 20v that could be supplied by the Taurus. Maplin psu's suffer from the same limitation and Maplin do not advise using psu's with different voltages from that required by the computer.

Do you happen to know of any universal power supply that can supply 19.5v? Do you think it is worth risking the Taurus - if so I presume you would recommend the 19v rather than the 20v setting? Do you know of anyone who has successfully used such a power supply with my particular range of Vaio (the VGN range)?

I would appreciate any help you can give me. Many thanks for all your excellent articles in SOS over the years (it is a sign of the times that I always turn first to your series when I open SOS!)

Best wishes

Ian Jenkins

I upgraded to a new Toshiba Satellite Laptop recently, and unfortunately i also got a very invasive ground loop with it!! After trial and error i found the problem was the laptops PSU. I tried various ways to stop the 'noise' and the best solution i found was this:

http://www.maplin.co.uk/Module.aspx?ModuleNo=46830

Its a tad pricey for a 6 way plug! but its virtually irradicated the noise in my monitors =)

Hope this helps someone!

Welcome to the SOS Forums JKD Productions!

I'm glad that sorted out your problems, but I'm surprised it did, since most laptop ground loop problems are related to the laptop PSU ground connection, while that 6-way mains conditioner only deals with RFI problems, and is unlikely to do anything to ground loops at all.

Perhaps you simply rearranged all your mains connections and reduced the problem.


Martin

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

Thanks for the reply Martin

I took my laptop, along with my mains filter to my friends studio today. The ground loop was there with me, the filter made no difference at all! Which confirms what you have said!

I do understand what you are saying, but at my studio at home it clears up almost completely? The only reasonable explination is that i run all of my gear through this one 6-way socket (2 monitors, 1 display, laptop and mixer)

Strange old thing groundloops. Iv done a bit of research and it seems thers not really a solid cure.

My only thing is that if the problem has been isolated as the PSU, surely you must be able to switch to a different model PSU??

--------------------
http://www.myspace.com/jkdmuznic

Hi JKD!

Ground loop noises can be greatly affected by how everything is plugged into the mains supply (different wall sockets, distribution boards, and so on, length of individual mains cables, audio cables between the different items of gear, etc. etc.) Your approach of a single 6-way dis board into one mains socket is always the best way, since it minimises the 'size' of the ground loop.

As for switching to a different model laptop PSU, you are quite correct, which is why I wrote a FAQ on this very subject entitled 'Curing Laptop Ground Loops with a Universal Power Supply':

www.soundonsound.com/forum/showflat.php?Cat=&Number=690190


Martin

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

Thats great, Cheers!

I have just one last thing to ask you on the subject that would apply to everybody with my problem!

My previous laptop's PSU didnt do this, so is my new one faulty? If this is a fualt, surely this would be covered by my warranty?

--------------------
http://www.myspace.com/jkdmuznic

No, it's not a question of being faulty - many modern laptops have metal cases, so I suspect this is one reason why they are invariably shipped with earthed PSUs.


Martin

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

In fact a lot of the noise appears if I haven't even got them plugged into the mixer and just have the mains pluf of those keyboards plugged in (yet the powered off!!).

--------------------
MAC DVD to AVI

Yes, ground loop problems can occur even when gear is plugged in but not switched on - as long as the loop has been completed the annoying noises can be there


Martin

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