Mic vs. Line Input Impedance

[pietro79]

Hello

I'm trying to clarify for myself the relationship between Mic inputs and Line inputs and their impedances.

My logic is that because a mic gives out a low signal (compared to the higher signal of a line level), then it should mean that a mic input is expecting a low signal and therefore has a low impedance, to try and facilitate the reception of that low signal. Is this correct?

If so, then Mic inputs have lower impedances that Line inputs, right?

Are there standard input impedances?

Any good websites for beginners?

Thank you for you patience!
pietro

 

[ciminosound]

Well I'd certainly recommend you click on the Meta-Meta at the top of the pages here and get reading. Lots of info in here. And use the SEARCH function up on top too, you can answer a lot of your own questions. Welcome!

Gerry

:sam:

 

[ciminosound]

My logic is that because a mic gives out a low signal (compared to the higher signal of a line level), then it should mean that a mic input is expecting a low signal and therefore has a low impedance, to try and facilitate the reception of that low signal. Is this correct?

No, there are high impedance mics too. Level of signal and impedance are different things. Not exclusive to each other.

If so, then Mic inputs have lower impedances that Line inputs, right?

Balanced mic inputs for lo-z mics are. They tend to like to be loaded with around a 150 ohm source. Modern line level inputs are 10k thru 47k ohms generally speaking.

Are there standard input impedances?

Sort of. Ususally within a range. Old transformer based gear is different than modern gear, again generally speaking. Modern gear tends to be "bridging" inputs which should be at least 10 times the output imp. of the gear inputing to the device.

 

[CJ]

Level differences are important when looking at input transformers.

Condenser mics send out a hot signal, so you will see large input transformers on the modules meant to handle them. Look at the input for the V-72. 625 EI! Massive! 20 db all day long. Not a problem. Line or mic.

SM-58 putting out 20 db? Not unless your Pavarotti or an F-14 afterburner.
So you will see smaller input iron on the more "normal" types of mic pre's.

You want to match the level with the transformer so that you do not waste anything, like signal level, or Supermalloy.

Here are three cores being worked at zero level, 1/2 throttle, and full throttle.

You would like to get at least half the core working at nominal input levels, I would imagine.