Laptop Line-in vs. Microphone-in

Great forum here. I’m new to most of this; please bear with me.

After searching the forums, I’m still somewhat confused regarding laptop input(s). In my specific case, I have a Compaq Presario CQ50 with of course 2 front panel 1/8" (3.5mm?) mini jacks. One for output / headphones, one as microphone or line input.

Here’s where my questions start:

  1. Is the input line or microphone or both?
  2. If microphone, can I assume that it’s only monaural / single channel?
  3. If line, will it accept a stereo / 2 channel signal (assuming I have a TRRS mini plug)?
  4. If both (mic & line), is the electronics smart enough to sense the signal being low as a microphone (and hence amplify the signal) or high as a line (and hence not amplify the signal), and switch accordingly? Is Audacity smart enough to “know” if I choose line over mic that it expects line?

Seems like I read on Shure’s site that most laptops have a line input, but I can’t remember the page. On this site, it seems like most agree that laptop input (when only one) is a true microphone input. On Campaq’s site, it’s listed as a microphone input. Yes, I’m confused.

  1. If a mic input, would a recorded signal distort badly if a line input is fed? Or, would it depend on the line signal strength?
  2. Since a microphone input is approximately 3 orders of magnitude less (voltage) than a line input, is there ever any overlap? I.e. is the greatest expected microphone input still less than the least expected line input? In this case, I could understand the electronics being smart enough to know if mic vs. line.
  3. Finally, would I just be better going with a USB input device like the Behringer UCA 202 and not even worry about the front built-in jack?

Thanks men. Sorry for all the questions.

Some Windows laptops have one audio input that can switch between two different services – Microphone and Line.

You need to go into the laptop hardware services to figure out what to do. Some of these services allow you to change the hardware in the Windows control panel.

Line-In typically is high level, stereo and takes a Tip/Ring/Sleeve connector (one ring). The headphone out of an iPod is line level as is the audio output of most CD, DVD, and Cassette players.

Mic-In is very low level mono, but still takes a TRS connector with a variation.

Mic-In connections typically have software arrangements where the one microphone appears on both left and right. Some just give you mono and have a happy day. These connections were designed for a communications system like Vonage or Skype. Most communications headsets will plug straightaway into a Windows machine.

Macs don’t work that way.

You know immediately if you get the wrong one because you either get no sound or hideously distorted sound. In rare cases you can damage the computer by picking the wrong one. Start the computer expecting Stereo Line-In. That’s harder to break.

<<<Shure’s site that most laptops have a line input>>>

Most Windows Laptops have a Mic-In. Macs have Stereo Line-In. Most Windows Deskside machines have both.

We use the thousand to one rule. Microphones generally are a thousand times quieter than line connections. There are hot microphones out there and low level Lines, but that’s good to go on. The problem with trying to hit it in the middle is the microphone. Microphone level is roughly the same level as noise generated by electronics. You can’t mess around much without killing the microphone quality.


Thank you for taking your time to reply in such detail. I appreciate it very much.