Line level input?

[airman00]

Over here by the DTMF  decoder  it says the following
" Onboard RCA audio input jack for line level inputs "

Now what exactly does that mean ?

I want to connect the decoder to the headphone jack of an MP3 player  using this adapter


Do MP3 players give out line level outputs, or would I need an amp for it?
I have a feeling I would need an amp , but if I do need one , can I just use a standard op amp?

[AndrewM]

http://www.transom.org/tools/basics/200207.analogbasics.html

Most electronics, except for standard microphones, output at line level.

[Admin]

if I do need one , can I just use a standard op amp?

There are op-amps specifically designed for audio applications. When you browse the digikey selection, it will have that option.

[Soeren]

Hi,

" Onboard RCA audio input jack for line level inputs "

Now what exactly does that mean ?

Line Level used to be a standardized measure (although different in the consumer range and eg. broadcasting) - for consumer goods, which this project is probably referring to, Line level is 775mV RMS.

These days, the term has been watered down to the point of near distinction, trough the multitude of far east products where "Line Level" can be anything from 100mV to 2V.

Even so, when you meet the term, at least you know that a microphone won't do