pc sound card question

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ghostman11

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does anyone happen to know what the max input voltage on the line in socket is on a normal pc sound card, i have trawled a bit and from what i have read it seems to be around 0.7 volts! this seems realy low to me.
the end app is to connect a pic to it so i can amplify sound out put from an alarm.
 
I think the .7 volts guess might be a bit high, line in voltages are supposed to be around 200mv's
 
Be careful which and what kind of attenuator you use, since this are relatively low voltages you could get more noise than signal, so carefully observe S/N ratio. Resistors by themselves always inject electrical and thermal noise.
 
jhanus said:
Be careful which and what kind of attenuator you use, since this are relatively low voltages you could get more noise than signal, so carefully observe S/N ratio. Resistors by themselves always inject electrical and thermal noise.
Click to expand...

It's not any kind of problem, these are line level signals, which are a relatively high level - far, far, above any kind of resistor noise.
 
are there better ways to increase sound output from a pic?? i need a fairly loud alarm signal
 
ghostman11 said:
are there better ways to increase sound output from a pic?? i need a fairly loud alarm signal
Click to expand...

What has a PC got to do with it?.

You just need an amplifier and speaker, of as much power as you require.

How loud do you want it?.
 
the pc idea was purely to plug the output from the pic into the line in or mic of sound card and play the alarm thru the pc speakers, i need it fairly loud so it can be heard at a distance,
 
ghostman11 said:
the pc idea was purely to plug the output from the pic into the line in or mic of sound card and play the alarm thru the pc speakers, i need it fairly loud so it can be heard at a distance,
Click to expand...

How loud, and at what distance? - and exactly what is the signal?.
 
loud enough to be heard from inside one building to another 20-30 feet away and the signal is 5v from a pic.
 
I would suggest you probably need a fair amount of power to hear it inside a different building 20-30 feet away.

Are the PC speakers loud enough?.
 
the speakers i had in mind plug into the mains and when they are on full they are realy loud!! but i have no idea of the specs, i guess my other option would be to lay a cable into the office from the outbuilding and have a smaller speaker with some kind of amp
 

Assuming they are PC Speakers, then they have an internal amplifier, so you can feed them from the PIC via a simple resistive attenuator - try a 10K and a 1K.
 
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