LCD monitor produces noise

SteVe · Post by **SteVe** » Wed Dec 08, 2004 2:41 pm

Since I got my new LCD Monitor (acer AL299) I have a disturbing signal on my analog inputs of the scope card. It makes no difference running the monitor in connection with the apple G4 or with the PC. What to do?

interloper · Post by **interloper** » Wed Dec 08, 2004 6:09 pm

Power conditioner with noise filter might do it. It would be advisable to try the conditioner out, if possible, before making a purchase.

Otherwise, you have balanced inputs? If so, try balanced cables.

LCDs produce less radiation than CRTs, so this is pretty strange.

<font size=-1>[ This Message was edited by: interloper on 2004-12-08 18:09 ]</font>

Post by **garyb** » Wed Dec 08, 2004 8:04 pm

gound loop?

SteVe · Post by **SteVe** » Thu Dec 09, 2004 11:41 am

Thanks for your ideas. The LCD screen is connected over the DVI.
The Radiation is not the problem. There are no problems with a ground loop. Even with everything unplugged the noise is still sending its signal to the analog inputs.

astroman · Post by **astroman** » Fri Dec 10, 2004 8:14 am

I assume you shut off the TFT screen and the noise is gone, right ?
In that case you have 3 possible sources of emitting noise:
the (probably) external switching powersupply of the screen,
the DVI output stage of the video card and the connected cable
and finally the screen electronics

for simplicity connect the screen with an analog cable (if it has that kind of input, too) - noise gone ?

is the video card firmly connected to the computer case (which itself should be grounded) ?
Sometimes coloring of the case prevents proper ground connections.

a DVI signal IS a heavy noise source due to it's nature of nothing but 'square waves'.
It doesn't require much electrical power (in watt) as every everyone can check with a cellphone close to an analog input.
The connectors themselves (and the lines on the circuit board) act as antennas when picking up the noise.

cheers, Tom

grabie · Post by **grabie** » Fri Dec 31, 2004 2:12 pm

I got the same problem.
So now I wonder what helped.

SteVe · Post by **SteVe** » Mon Jan 03, 2005 5:17 pm

The Problem is not solved by changing from the DVI to the analog cable. So - what to do?
I dont have the problem with a new EMU sound Card in my PC.
I like the Creamwarestuff a lot, but they sold me a great antenna, called "analog inputs". What to do??

Herr Voigt · Post by **Herr Voigt** » Mon Jan 03, 2005 5:50 pm

I would use only fat protected cables. Or, if nothing helps, mute the analog in and use only the ADAT and SP/DIF ins.

Liquid Len · Post by **Liquid Len** » Mon Jan 03, 2005 6:40 pm

I agree with Herr Voigt. You probably don't want to hear this, but you're better off not using the analog ins anyways. I always use spdif or ADAT in, having the AD/DA convertor right on a soundcard is not optimal design. You want the AD/DA conversion process to take place in a proper shielded environment - that's why cards like the MIDIMAN deltas have breakout boxes, to remove the AD/DA conversion process from the inside of a computer to a less interference-prone area. In fact, they sell a special breakout box that requires a 9v adapter, so the mike preamps and AD/DA conversion process are on an isolated power source, separate from the computer's.

astroman · Post by **astroman** » Mon Jan 03, 2005 8:02 pm

On 2005-01-03 17:17, SteVe wrote:
... but they sold me a great antenna, called "analog inputs". What to do??

I somehow (have to) agree, but it's defininetely not the cards fault - and I disagree about non using the analog ins.
Those have great converters (imho) and I never HAD a problem with them...
until recently, now I do HAVE exactly an antenna problem.

Read the miracle: with nothing connected to the analog ins they show -85db noise floor, perfect for a Pulsar One, same as it ever was.
I plug in a 2m cable with dangling ends and the noise rises a bit (expectable) to -82 dB.
Now if I connect some gear it can go up to -55 dB, no matter if that thing is turned on, off or even disconnected from power.
And it picks up that mouse-fader zipper noise

The observation above refers to a wall-wart supplied Yamaha. I just tried it with a Protheus 2 and a TX802. Similiar noise level, but switching on/off and disconnecting the power cable had a varying influence.

Switching the TFT on and off had no influence at all.

Obviously the card alone behaves well, but depending on what's connected externally it picks up noise from the surrounding.

I recently moved to a new flat in an old house, so I assume it's due to installation peculiarities - I'm not even sure if the thing is grounded at all...

But since I'm already in love with this house, I just overlook this little annoyance and rely on my A16, which doesn't show this behaviour.

Don't take the analysis above for granted - it's just an example that there may be things out of immediate control - I really didn't dig too deep - but at least I can tell that the central heating IS NOT grounded

cheers, Tom

Liquid Len · Post by **Liquid Len** » Mon Jan 03, 2005 9:12 pm

I don't mean to disparage the analog ins on the card, it's just that if you are experiencing noise problems while using them, I think it is somewhat to be expected. Recently I've been forced to use the analog ins, for some reason on my system the left side picks up noticeably more noise (but only when plugged into some piece of equipment). Even the right side has *some* noise, but I can live with it. I've had a number of soundcards that had a convertor built into the card, and they ALL exhibited noise pickup. I'm not saying that such a card does not exist, but I haven't yet used one. If you can live with the noise that the analog ins add, it shouldn't be a problem. As for quality of conversion, it wouldn't surprise me if the quality of those convertors on the card is very good, as I recently A/B'd a Behringer mixer against the convertors built into the Noah, and found the Noah's sounded noticeably better.

Post by **garyb** » Mon Jan 03, 2005 11:06 pm

ground the ac properly and there should be NO analog in problems....