Re: Acceptable voltage levels in Line-In and Mic inputs

There are two issues to acceptable input voltage levels 
- possible damage to the input circuitry
- possible damage to the output device and your ears

Input

The likely maximum required input to the analogue amplifiers will be a few 
hundred millivolts (there used to be some form of standard that defined 0dB 
(maximum input) as 775mV (i.e. less than 1 volt)

Since whenever operational amplifiers have been able to cope with inputs of 
several volts (one device IIRC could cope with +/- 15 V - for those that care 
the input is clamped using "zener diodes"

so probably no need to worry too much unless you've got plans to shove 110 V 
into the input

Output 

Well before you can damage the input circuitry you will "overdrive" the input 
(it's how fuzz pedals for guitars work, for those that care)

This will cause the circuit to both go non-linear (produce high frequency 
harmonics) and produce clipped waveforms at the output. (the power supply 
cannot produce big enough voltages for the required gain)

This is a fantastic recipe for executing tweeters in hi-fi loudspeakers or for 
causing pain to those of you wearing headphones

HTH  

 


On Monday 30 August 2004 22:51, Rafael E. Herrera wrote:
> Hello,
>
> What are acceptable voltage levels, max an min, for the audio inputs of a
> typical sound card.
>
> I'd also like to know what kind of protection a sound card may have for
> overloading.
>
> Thanks.
> --
>    Rafael