At the top of the Jam+ is a headphone output dedicated for monitoring both your computer playback as well as your direct guitar signal. The mix of the two sources can be controlled using the controls on the front of Jam+ - Click once for a 50/50 split between your instrument and the USB playback, click again for 100% USB playback.
Having the option to select a 50/50 split of your instrument and playback allows the Jam+ to deliver a true, zero latency monitor mix that feeds directly to your headphones. This means that the instant your pick hits the strings, the sound comes out of the headphones with no latency (meaning no delay between hitting the strings and hearing the sound). If your signal was run through the computer first to be processed before reaching your headphones, that extra trip would cause the audio signal to be heard slightly after the initial strike of the strings which can be quite uncomfortable whilst recording. All this means is that with Jam+ in 50/50 mode, you never have to worry about latency issues putting you off recording the perfect take.
You can hear more about the importance of Zero latency monitoring during guitar tracking in this little snippet of the video, where Grammy Award-winning guitarist Brent Paschke writes a ‘Katy Perry-Inspired' track using his Jam+ and an iPad!