I don't think my internal mic is disabling when I use the line in mic socket

related to my issue with speaker feedback. I have reason to believe that it is because my internal mic is not disabling correctly when I switch to line in mic socket.

It sounds as if as well as picking up my guitar from the mic socket it is also picking up sound from elsewhere.

How can I locate the internal mic and block it to test?! Or any other solutions??

My 13" MBP disable internal Mic automatically whenever I plugin iPhone's headphone or iRig adapter

BTW I need more info

Which mac do you use?

How you connect your guitar?

Which software do you use to record?

Hi, thanks for the response. I use an imac G5 1.6ghz, 1gb ram 150gb hd. using garageband to record. I connect my guitar through a 6mm to a 3.5mm cable from guitar to mic socket on back of mac.

like your mbp when i go into audio settings in sys preferences my inernal mic disables as it should. when i go onto garageband to record it sounds like it re enables itself because of the feedback i get and its not only when guitar is plugged in. even if there is no cable plugged in at all but the garageband monitor is on i get the feedback.

i have a youtube video demostrating what happens

Mac speaker feedback issue in garageband - YouTube.

hope to hear from you soon.

Normally it shouldn't act like that. The internal mic should disable automatically when ever line in is plugged with right type of connecter.

The only reason that your iMac didn't disable internal mic because you use 1/8" TS to 1/4" TS adapter. The 1/8" TRS input jack of your iMac didn't detect all three-conductors (Which are Tip Ring and Sleeve) that's why it didn't tell your machine to turn off internal Mic.

You'll have to get Y-cable that split from 1/8" Stereo TRS to 2 mono 1/4" TS Jacks. It looks like this.


Be careful don't buy headphone splitter. They look very similar to each other.


Or 1/8" TRS to 1/4" TS Cables like this is OK to use too. This is 'Monster iStudioLink Instrument Cable' cost around $26


Y-cable or Instrument Cable can be DIY but you should use high standard cables and connecters such as Canare, Mogami, belden, Neutrik, and etc... It's a lot better than cheap pre-assembled cables and cheaper than expensive cables such as belkin, monster and etc...

I've been using Canare cables with neutrik connecters in my studio for more than 10 years and all my cables still working fine.

btw after you've solved Feedback issue with these cables you might get another issue because plugging in Hi-Z guitar's output in to Lo-Z computer's input might cause 'Impedance mismatch'.

Impedance mismatch can be acceptable to some people, So you might be OK with it. But If you'd like to get better matched signal you may consider to buy mic preamp or audio interface that have mic preamp at later time. (most of them have instrument inputs as well. So you can record both mic and instrument. Well... I think it's good investment though.)

cheapest mic preamp that I can think of is 'SM Pro Audio XPM1 Single Mic Preamp' $49.99


or Audio interface like this one 'Focusrite Saffire 6 USB' $199.99