can i change between internal speakers and headphones ?.Thanks

Hi, sorry, but I'm not sure I fully understand the question. The app lets you make any standard audio device the current default (or "system") output. So for instance if you have the internal speakers playing and you have a USB headset plugged into your mac, then properVOLUME will let you switch the output to the USB headphones (and back to the speakers, of course). Is that what you are asking?