pc sound card question

[ghostman11]

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.

 

[Nigel Goodwin]

Connect it via a simple resistive attenuator.

 

[ghostman11]

cheers nigel at least i now know what to ask google

 

[Sceadwian]

I think the .7 volts guess might be a bit high, line in voltages are supposed to be around 200mv's

 

[jhanus]

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.

 

[Nigel Goodwin]

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.

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.

 

[ghostman11]

are there better ways to increase sound output from a pic?? i need a fairly loud alarm signal

 

[Nigel Goodwin]

are there better ways to increase sound output from a pic?? i need a fairly loud alarm signal

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?.

 

[ghostman11]

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,

 

[Nigel Goodwin]

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,

How loud, and at what distance? - and exactly what is the signal?.

 

[ghostman11]

loud enough to be heard from inside one building to another 20-30 feet away and the signal is 5v from a pic.

 

[Nigel Goodwin]

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?.

 

[ghostman11]

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

 

[Nigel Goodwin]

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.

 

[ghostman11]

ok great i will give it a go later,