Ground Hum when Laptop is Connected to I/O Device.

[named]

Hello,

Sorry for beating the ground hum horse, but I've poured through a ton of posts and read a number of web tutorials on grounding issues to no avail.

When I listen to this laptop with headphones connected to it direct, no hum/noise.

When I connect a M-Audio 410 Firewire device to it, and monitor the laptop through headphones connected to the M-410, no hum/noise.

But.

When connecting laptop to numark dj mixer and/or amplifier via a stereo mini to RCA cable, hum&noise.

When connecting laptop to M-410 and then connecting M-410's outputs to Numark and/or amplifier, hum&noise.

So, the Numark and amplifier do not hum when connected to any other device. Other devices tested; Boss drum machine, cd player, dvd player, Yamaha sampler, Korg drum machine. All of these devices have been tested solo and combined. The buzz only occurs when the laptop is connected. And the notebook only produces the buzz when connected to a third device.

The laptop manufacturer claims no fault. I've tried removing the hum by connecting the laptop to a Behringer DI box that has a "Ground Lift" function. Laptop + firewire out + M-410 + unbalanced output + Behringer unbalanced output + mixer or amp= Buzz/NOIze.

The buzz doesn't seem like a standard ground buzz, as I can here the computer doings its bleeps and creeps.

Any help on what to do, where to start, what the cause is would be much appreciated.


Named

[jpw23]

The laptops disply may be the cause of the hum....much like a florecent bulb...in my studio...the monitor can cause some hum when it is near other audio equipment

[jpw23]

also.....not trying to cut down your equipment...but, numark is not the best in audio......it is meant for dj's and their world is a noisy one!

[jpw23]

by the way.... this is what i do for a living....i install sound systems in churches, schools, ect, ect,....and all i use is sound tech commercial grade equipment

[named]

Jdw & Peeps;

Thanks for the suggestions.

I have tried the setup on more reputable mixers (vestax and pioneer)with the same results. When the notebook is added the buzz exists.

Since the buzz does not exist when the laptop is soloed in the manner I put forth earlier; can I concluded that in any of these various other setups their is another device in the signal chain causing the noise? If that is the conclusion, then why does the buzz only occur after adding the laptop? Shouldn't the setups also buzz when the laptop is disconnented?

Thanks again for help

Named

[wockachucka]

Does the hum go away when the laptop is powered by a battery only? Or powered by AC only?

Do you have a docking station?

Do you possibly have another AC adapter you could try? Or another battery?

What kind of power management settings do you have available in the computer's BIOS?

If it happens when on AC only, does plugging it into a different circuit help?

[wockachucka]

LOL cracker...I guess you took the words out of my mouth, didn't you?

Also....the laptop's display won't couse the interference. Only CRT monitors do that.

[named]

JDW, Ed, Chucka, Peeps;

Thanks again.

Phantom power is disabled. Battery-only power creates a similar result. I do use a USB KVM/monitor switch (do they qualify as a docking stations?). I have tested this at other venues w/o switch, buzz remains.

Is it recommended that all devices be plugged into the same surge protector?

Another thing that perplexes me is that the noise occurs when routed through the firewire device. Can ground/noise/hum be rendered digitially down the firewire cable to an interface?

Named

[This message has been edited by named (edited 01-20-2004).]

[wockachucka]

No, for the purposes of troubleshooting this problem, you want (if at all possible), the laptop to be powered off of a different circuit entirely. However, if it does it on battery power as well, that's not the issue (maybe). Can you take the battery out entirely and run it on AC power only? The battery may have a short.

Do you have a different battery to try?

When I say "docking station" I mean a proprietary shell that you drop the laptop into when you are at "home" or in your "office." It has many extra ports, it's own AC power supply, etc. It's not a port replicator that plugs into a USB cable and gives extra ports....if you're using that, take it out of the equasion somehow. Does your laptop have it's own firewire port? If so, that's what you want to run it through...not a port replicator.

[named]

The M-410 is connected directly to the laptops firewire port (4 pin to 6pin if I'm remember correctly).

I will try removing the battery and run on AC power only. With this setup do you still advise connecting all devices to an outlet on one circuit, except the laptop which connects to an outlet on a different circuit?

Before booting up on this setup I will also subtract the KVM switch from the equation.

Thanks again.

[wockachucka]

If the other devices have worked OK on the same circuit before with no hum, than generally it shouldn't be a problem. BUT.....it may be some kind of environmental thing. Forgive me if you've already answered this, but does it do the same thing with the exact same hardware setup in another location?

What kind of laptop is it? Make? Model?

[This message has been edited by wockachucka (edited 01-21-2004).]

[named]

Hey all check this out!!!!

I've posed this same question on a different board...Galvanic loop??? Read on:
http://forum.cubase.net/forum/Forum2/HTML/060474.html

[named]

I've tested this in different locations with similar results.

brand: Pro Star model:5694.

please also check this link:
http://forum.cubase.net/forum/Forum2/HTML/060474.html

Can anybody expand on this?

[Neil Wilkes]

This noise is induction related, and is caused by the transformer in the Power supply unit.
There is no way around it, short of a much better quaslity PSU with an isolating transformer.

[named]

Thanks for the additional info...

Should I assume that this is a design flaw in the PSU, and that replacing it with the same model PSU would yield the same result?

Can I use a 3rd party PSU with an isolating transformer without compromising the laptop?

[bubba freaktree]

laptop displays do *not* cause hum. they are lcd. that's one of the huge benefits, and why any self-respecting daw owner/operator will have their displays 100% lcd.

ground loop hum is often caused when you have two different circuit breakers in your electronic loop. if you plug into two different outlets and those outlets are on different circuits, you can often get hum because the ambient current will flow in a loop around and around the whole circle.

so put all your stuff on one outlet, one strip if you can. it is highly unlikely you will overload your breaker, because audio stuff is really mild compared to power suckers like electric heaters, vacuums, hair dryers, table saws, etc.

also, 1/8" stereo mini to spread rca is not a great connection at all from a noise standpoint.

Originally posted by jpw23:
The laptops disply may be the cause of the hum....much like a florecent bulb...in my studio...the monitor can cause some hum when it is near other audio equipment

[wockachucka]

"Should I assume that this is a design flaw in the PSU, and that replacing it with the same model PSU would yield the same result?"

As stated earlier, if it does the same thing whether powered by battery alone or by AC alone, then neither is the contributing factor.

[named]

Ohhh yeahhh...forgot about that whole battery thing for a second, guess I was a little to excited about finding a possible fix. Thanks for getting me back on track Chucka, but I'm still stuck on how I should move forward.

The board linked above suggested:
"A transformator linebox for every output on the 410"

I have no idea what that is. Can't find one internet searching... any ideas on what they were getting at?

[jpw23]

american music supply sell a handy dandy little tool for just such situations, it's called " hum eliminator" or " hum exterminator" or something like that....just route the offending device through it and no more hum..........musicians friens also has this product.

[wockachucka]

Still wondering if you've set up the exact same hardware in the same configuration in a different place.

It could be some bizzare environmental electrical interference specific to the location that you're in.

[named]

Peeps.

Thanks for checkin' back Chucka.

I tested the laptop last night, battery- powered and got the noise. I tested it tonight on a club system, battery-powered with no noise. When I added the PSU the noise resurfaced. So it looks like I'm back to the PSU suggestion.

But. I'm wondering if their is any other options aside from the new power supply, as new one's are $90.

Other than the noise, the power supply seems to check-out ok (not that I have any idea what qualifies a PSU to check-out ok, but it hasn't seemed to cause any noitceable issues). And I don't want to buy another power supply to find the replacement doing the same thing due to a design flaw.

That said, would you buy the power supply first or try a different device to eliminate the noise. (have already tried ground lift option on DI).

Thanks again for the helping.

[named]

Chucka, earlier you asked about my power management settings in the BIOS.

Do you have any links handy on how to setup BIOS power management settings correctly, or if it's simple could you post directions?

I run PHOENIX BIOS.

Thanks.

[wockachucka]

Originally posted by named:
1. I tested the laptop last night, battery- powered and got the noise.
2. I tested it tonight on a club system, battery-powered with no noise.
3. When I added the PSU the noise resurfaced. So it looks like I'm back to the PSU suggestion.

Now I'm confused....hehe

So in the first location, with AC power only, noise or no noise?

Depending on how you approach the tech support guy from your computer manufacturer, you can probably convince them to send you another AC adapter for free (assuming it's still within warranty). I'd try to eliminate that.

[Afrotronic]

Have you tried external power on the M-Audio interface?
What about better, i.e., balanced cables?

[named]

Hey Y'all;

The noise is present at all locations with the AC connected.

I've tried the M-410 with its own power, and balanced cables, the hum still exists.

I guess I'll give the new power supply a try, and post back.

Thanks,

Named

[ducktail]

I believe the problem is due to your laptop having a switching power supply. Had exactly the same problem. Lift the ground. Simple

ducktail

[kinky]

i have already have had this problem: your hard drive has no ground. and when you connect to external gear which are connect to AC, they have a gound so noise appear!!! and the best is just that there is no solution... in fact i haven't fount it right now and i'm still looking. good luke

[named]

Peeps,

Ok so I'm back to report that I've tested a new power supply, and am getting the same results.

Please help with any additional ideas.

Named

[brzilian]

Originally posted by named:
Peeps,

Ok so I'm back to report that I've tested a new power supply, and am getting the same results.

Please help with any additional ideas.

Named

Doe the laptop have a 3 prong grounded plug? If it doesn't thats probably the cause of your problem. Not much you can do to fix it either.

[Bops2000]

I'll give it a shot
perhaps a preamp is needed,
like a radio shack thing....
(I applaud your patience, as that laptop
would be in the neighbors yard by now if mine..)

[named]

Kink,

Is it technically feasible to ground the hard drive? Have you tried it?

Thanks,

Named

[named]

Bops!

Thanks for your suggestion...I've tried using a Behringer DI with a ground lift function; but that didn't do the trick either!

I'm taking it to a local tech today...will post results for all you with similar issues.

Named

[This message has been edited by named (edited 03-10-2004).]

[melloman]

Here's something to try...
The Numark has a grounding spot, and while the laptop doesn't actually have one, there's a spot that will probably perform well enough as one. Your connections for serial and parallel on the back have holes for the cable mounting screws, that connect to the I/O shield. If you connect to that, then connect to the Numark, this might allow both of them to share ground. If you have tried 2 power supplies to the same result, then your grounding for the laptop is probably what will need help.

[rumba]

Hello named!

If you search the forum, you will see that I posted a question that noone answered and I could solve it myself concerning the same problem you have.

There is no problems with laptops or whatsoever but problems using the m-audio external cards ->(drivers). In my case; I use a Toshiba Satellite P20 304 and a friend of mine has a different Laptop from SONY with same problems of noise with a firewire m-audio card.

Read below! First M-Audio told me to ask Toshiba if these laptops are well grounded; result: YES, they are well grounded.

Except your laptop is not well grounded, thing that i don´t believe, m-audio USB cards and firewire cards have extrem problems with its drivers.

I had tech support from the m-audio and they finnally recognized to me by email that the drivers don´t work well in every system.

In the shop where I bought the M-Audio DUO USB Card, they saw by themselves that it was not possible to tune anything with these drivers from m-audio. Bad installation process, sometimes the drivers don´t install and so on. The card DUO sounds very good for sure but the drivers destroys the whole product.

We made a whole installation of XP 2 times and one time win98 to instal only these drivers and to make sure the drivers install and work ok, but it was not possible to do so.

I solved the problems by leaving the m-audio DUO card back to the shop and changing it for a TASCAM US 224. All the hum and noise problems I had, are totally gone, in other words, I am very happy that I changed for the better and all goes so good. This card is a great one with great sound full of options and very robust drivers. No delays or whatsoever using the USB Tascam with the laptop. The laptop goes so quiet that it seems nothing is turned on.

My tip: Chage the m-audio card due they are not ok with those drivers.

Sorry that it sounds a little brutal against a branch (m-audio) that i really respect. Maybe some people in the forum have no problems using these usb/firewire m-audio, but, the info I have, and I repeat is: DRIVERS ARE NOT OK!

rumba.

[This message has been edited by rumba (edited 03-07-2004).]

[named]

rhumba;

Thanks for that, unfortunately this noise occurs in the analog output of the laptop as well as the M-Audio/

mello;
That's a tasty suggestion, will I be compromising the hardware by doing this? I've heard of 'ground lifting' were you go from 3 prong -> 2 prong, and that it's very dangerous...


kink;

Have you tried grounding your hard drive? Was it sucessful?

Peeps;

The local computer tech is still diagnosing the problem, will post results.

Named

[named]

Peeps,

The computer tech has confirmed a faulty motherboard, and I'm sending it in to get fixed...will post results, hopefully this resolves the issue.

NAmed

[jpw23]

Going from 3 prong to two prong is not dangerous...the nuetral wire on your recpticle goes to the same buss in your breaker box as does the ground wire, the third prong is a redundant ground....the only problems you might face with 2 prongs is that your surge protector reads the potentia to ground from that 3rd prong...therefore....surge protection is no longer valid....btw....surges rarely smoke a pc....it's the low voltage conditions that take out pc's and other devices, spikes will do the same but, they are rare as well....you get spikes from god almighty...lightning bolts!

[named]

JW,

Thanks for the clarification-

Named

[named]

Peeps,

Got the notebook back from the manufacturer with a replaced motherboard, and the noise is completely gone.

So, in summary. If you're notebook computer audio output creates excessive noise that can't be resolved with standard troubleshooting, ask the computer manufacturer to do a motherboard diagnostic...If they play games take it to a local computer tech and get a second opinion. It cost me $35 to have them test it, I could've saved alot of doe in shipping had I taken it to them in the first place. And always buy the extended warranty...

Thanks again for everybody's help....

[Soulja]

Maybe you've long figured out your problem, but I had the exact problem. It's the mixer or the AMP. Maybe both. The FW 410 is a bit more powerful and top of the line. I just ridded of my crappy mixer and amp set-up and invested in some Powered monitors. OFF THE HOOK!!!! I've since, hooked my 410 to other set-ups and with a good mixer, NO HUM. Anyways homey, I know I'm late in the game but better late, than never. Later

[whizz]

if you get a earth loop isolator from either halfords, maplin etc for each channel this should cure the problem. They cost around £10 - £15