Can't record output using Quicktime Player.

i used to use QT with soundflower but now i use the combo of QT and the free BlackHole Virtual Audio Driver. i don't know if iShow u capture used to work the same way as BlackHole, so i'll give you all of the steps as if it's new to you.

once BH is installed, in recording options you can choose BlackHole instead of Built-in Microphone.

you will also need to set up a multi-output device in your audio MIDI setup utility to be able to both hear and record the internal audio at the same time.

to set up a multi-output device:

Open Audio MIDI Setup: (found in /Applications/Utilities)

hit the '+' button in the bottom left corner and select "Create Multi Output Device"

then in the panel that appears on the right, in the Multi-Output Device tab, select "Built-in Output" AND "BlackHole 2ch". (and, if you want, any of your other connected devices.)

once you do that, (and BEFORE recording) you can choose "BlackHole 2ch" or "Multi-Output Device" in your menubar "sound options". 

to both hear the speakers and record the audio at the same time, choose "Multi-Output Device". before choosing multi-out, set the internal speakers' volume to a comfortable level first. you cannot control the volume once you are in multi-out mode.

and just FYI, to download BlackHole the developer asks for your e-mail address but they haven't sent me even one spam-mail.

you're welcome. and as far as the difference between 2ch and 16ch, "ch" stands for channel. for most users, 2ch is all that's needed. it means stereo sound. 16ch would be for someone that needs to combine multiple sound tracks, like for instance, a 16 piece orchestra.

no problem. i enjoy being helpful. :)