shielding

S

sonnylarsen

New member
Athlon 900
RAM: 352
sblive
98

So, my sound card ought to have a n2s ratio in the area of -85db, but when I record, I see that i have noise at around -60db. This noise is present all the time, no matter if the mixer is on or not. I have come to the conclusion is is electronic noise and that the card is not properly shielded.

As much as I would like to own and Aardvark, I simply cannot afford any other card and so I had an idea...I could add shielding myself! Why not, people do these sorts of things all the time. Aluminum should work, I think.

My question is, where do I install it? Over the inputs ( I use the line in) or should I shield the entire card? Or, maybe it is simply not possible and I should just continue to save for my new card and make do with -60d noise....

What do you all think?
 
sonnylarsen said:
Athlon 900
RAM: 352
sblive
98

My question is, where do I install it? Over the inputs ( I use the line in) or should I shield the entire card? Or, maybe it is simply not possible and I should just continue to save for my new card and make do with -60d noise....

What do you all think?
Click to expand...

Well, save for the Aardvark by all means! But, in the meantime...what you want to do is shield the whole card or at least where the a/d converters reside.
 
Think this over for a minute there man...you're talking about putting aluminum foil (a conductor) inside your computer. This has bad idea written all over it.

Noise at -60db with a soundblaster is not unheard of. Unplug everything from the soundcard and see where your noise level is at. If it's still at -60 and you can't live with it, try moving the card to a different PCI slot (the slot is not going to be to blame, but perhaps you can find a location where the interference is not so drastic).

Slackmaster 2000
 
I had a very similar problem a while back, so I asked an electronics gugu that worked in the same building.

He said to use a fairly fine metal mesh material (available at an electronics store) to allow air flow, and carefully shield the whole card, making sure it's grounded to the chasis.

Obviously, make sure that it's not touching anything else when you power up :)
 
And make sure it's not touching the CARD itself. The entire back of the card is going to be open solder joints.

Slackmaster 2000
 
Slackmaster2K said:
Think this over for a minute there man...you're talking about putting aluminum foil (a conductor) inside your computer. This has bad idea written all over it.

Noise at -60db with a soundblaster is not unheard of. Unplug everything from the soundcard and see where your noise level is at. If it's still at -60 and you can't live with it, try moving the card to a different PCI slot (the slot is not going to be to blame, but perhaps you can find a location where the interference is not so drastic).

Slackmaster 2000
Click to expand...

Slack,

He asked...I told. I actually work for an electronics manufacturing company. (Im the software engineer geek) I asked one of the double E's here about making a shield for cards using aluminum foil would work for RF problems and got a resounding yes.

But, let me clarify. You cant just wrap aluminum foil around the damn card. Thats not what I meant. You will need to make a metal shield or even plastic. I used a couple of old pcb's laying around for mine. Then line the thing with aluminum foil. Attach it securely to the soundcard. Voila.

With that said, it sure is a whole lotta work for a soundblaster. I did this for a Core 2 I have that was having some RF noise problems. Slack is right...dont just go putting aluminum foil everywhere...if you do...make sure you have a fire extinguisher nearby.
 
And one more clarification. Dont let the aluminum foil touch the soundcard...in fact, once I had my shield built I ran a line to ground which grounded the shield. This helped too.

Maybe I am saying too much.

Slack is going to blast me.

Just buy a new card.
 
I'm not going to blast anybody! Thanks for clarifying what you meant...I just wanted to make sure the guy didn't go wrapping his soundcard in aluminum foil or something.

Also, we need to make sure that he gets a noise floor reading without anything plugged into his soundcard, not even a CDROM drive, before he starts any sheilding project.

Which just reminded me of something....my old soundblaster had a noisy CD port (or the cdrom itself was noisy), and muting the CD Audio channel via the windows mixer took my noise floor down about 15db.

Slackmaster 2000
 
P.S. version2, I started my response before your first post had arrived...so I was directing my initial "think about it man" comments at sonnylarsen.

Slackmaster 2000
 
cool

Everything sounds good.

I want to clarify that my noise floor IS around -60, with nothing plugged into the card. I just checked that out.

Thanks
 
foil...

By the way, I just wanted to clarify that I was not thinking of haphazrdly throwing foil onto the card...some people might, I know, and its probably good that you said that for posterity and so on, but just to clarify...

oh yeah, and should I ground it to my system chassis, or the card?
 
Re: foil...

sonnylarsen said:

oh yeah, and should I ground it to my system chassis, or the card?
Click to expand...

Ground your shield to the system ground. Which, ultimately, is the same as the cards ground. But, you want to NOT touch the card as much as possible. So, make it a system ground on the motherboard. Im assuming you can find that ground! :D
 
Slackmaster2K said:
P.S. version2, I started my response before your first post had arrived...so I was directing my initial "think about it man" comments at sonnylarsen.

Slackmaster 2000
Click to expand...

;)

Well, I once told a guy this same piece of advice and he endedd up frying his mobo. I have NO IDEA HOW. :) So, when you said that I got defensive. Hehe.

Anyway, remember folks...when messing with electronics you can easily screw things up so take care. Make sure to keep your static charge at a minimum and ALWAYS unplug the damn machine before you start working on it.

And dont blame me for the black fingernails.
 
Most has been said, but for good measure you should shield both sides of the card. Go to a modelbuilders shop and look around for thin metal sheet. Brass will do nicely, is easy to work and can be soldered. Make a box for the card, solder all the seams. Then line the inside with plastic foil. After your finished, put also plastic on the outside. Make as much contact with the ground as possible.

Also to try: ferrites clamped over the cables.

Keep in mind that this will only help for radiated electrical interference. So magnetic interference will go right through. It will also not help for noise entering by the power supply of the card. Don't be disapointed if you spend a weekend on it and it does not help.
 
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