how can i protect my soundcard's input

Rixsta · 21st May 2004, 02:46 PM

Anyone know how to protect a soundcard input/output from a power spike while still getting good quality sound ?

Michael Rothacher · 21st May 2004, 03:32 PM

The usual method is a pair of back-to-back diodes.

Rixsta · 21st May 2004, 03:44 PM

Cool nice and eazy cheers do i do that on the ground and the singnal wire or just the signal ?

dont worry you need the ground dont you stupid me lol

dont diodes produce loads of distortion or is it ok because the diodes are back to back.

Also lol are they zeners ?

sam9 · 21st May 2004, 04:03 PM

They will distort as you approach the limit voltage. Lower level signals won't be affected much. The cut-ff is not abrupt and the effect probably won't sound offensive unless a high input is really sustained.

One thing you need to find out is: what is the maximum peak (not RMS) voltage allowed for your soundcard. The zener voltage needs to be a bit lower than that. For example, if the highest peak allowed was 6V, I would use two 4.3V zeners which results in a limit of approximately 5V so that you have a saftey margin.

If someone has a more precise rule or calculation, hopefully they will post it.

Rixsta · 21st May 2004, 04:14 PM

Quote:

Originally posted by sam9

If someone has a more precise rule or calculation, hopefully they will post it.

he he yep

exelent stuff you diy people rule
i take it that they protect against dc too

as iv'e said before on this site "im a bigginer to electronics" but hey im learning.

Thanks

rixsta

tiroth · 21st May 2004, 04:50 PM

I recommend some resistance in series prior to the diodes unless all of your sources are short-circuit protected. You don't want to protect the sound card by blowing out the source component when the voltage gets high enough for the diodes to conduct (or risk frying the diodes).

I used series-connected LEDs instead of zeners, supposedly much quieter.

As long as the series resistance is a reasonable fraction of the input impedance, you should be fine.

sam9 · 21st May 2004, 04:57 PM

"I used series-connected LEDs instead of zeners, supposedly much quieter."

Is there enough cuurent to light the LEDs when overcurrent conditions occur. If so, that's clever - I'm a sucker for flashing lights.

Rixsta · 21st May 2004, 05:26 PM

ok cheers people for now i will try the Led's

tiroth · 21st May 2004, 05:28 PM

Quote:

Originally posted by sam9
Is there enough cuurent to light the LEDs when overcurrent conditions occur. If so, that's clever - I'm a sucker for flashing lights.

Yep.

Just watch out, LEDs are not as robust as zeners--current limiting is mandatory.

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21st May 2004, 03:32 PM	#2
Michael Rothacher www.audiohobby.com diyAudio Member Join Date: May 2001 Blog Entries: 3	The usual method is a pair of back-to-back diodes.

21st May 2004, 03:44 PM	#3
Rixsta diyAudio Member Join Date: Feb 2004 Location: Cornwall	Cool nice and eazy cheers do i do that on the ground and the singnal wire or just the signal ? dont worry you need the ground dont you stupid me lol dont diodes produce loads of distortion or is it ok because the diodes are back to back. Also lol are they zeners ?

21st May 2004, 04:03 PM	#4
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	They will distort as you approach the limit voltage. Lower level signals won't be affected much. The cut-ff is not abrupt and the effect probably won't sound offensive unless a high input is really sustained. One thing you need to find out is: what is the maximum peak (not RMS) voltage allowed for your soundcard. The zener voltage needs to be a bit lower than that. For example, if the highest peak allowed was 6V, I would use two 4.3V zeners which results in a limit of approximately 5V so that you have a saftey margin. If someone has a more precise rule or calculation, hopefully they will post it.

21st May 2004, 04:50 PM	#6
tiroth diyAudio Member Join Date: Dec 2001 Location: Pittsburgh, PA, USA	I recommend some resistance in series prior to the diodes unless all of your sources are short-circuit protected. You don't want to protect the sound card by blowing out the source component when the voltage gets high enough for the diodes to conduct (or risk frying the diodes). I used series-connected LEDs instead of zeners, supposedly much quieter. As long as the series resistance is a reasonable fraction of the input impedance, you should be fine.

21st May 2004, 04:57 PM	#7
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	"I used series-connected LEDs instead of zeners, supposedly much quieter." Is there enough cuurent to light the LEDs when overcurrent conditions occur. If so, that's clever - I'm a sucker for flashing lights.

21st May 2004, 05:26 PM	#8
Rixsta diyAudio Member Join Date: Feb 2004 Location: Cornwall	ok cheers people for now i will try the Led's

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