This video demos's a RASPBERRY PI using FLdigi which is sending out a stereo signal from the pi's own analogue sound card to 2 individual audio derived cw circuits: see here: http://qrqcwnet.ning.com/forum/topics/what-circuit-for-computer
one keying circuit keys the PTT jack on the K3 , just before and just after the CW JACK is keyed by the 2nd circuit...
both circuits are adjustable in the FLdigi RT CHANNEL QSK control panel, and the FLdigi volume slider, so that you can optimize not only the ability of the K3 to send good quality CW NOTES above 100 wpm, but also improve the K3 CW ELEMENT length variance. NOTE: - the K3 will shorten elements when using FULL QSK...but FLdigi will bring the elements back into their intended timing...by activating the PTT to come into play and help out...
This K3 in the video was using FULL QRQ + mode
a SOFTWARE AUDIO OSCILLOSCOPE LV2 plugin on LINUX was utilized to view the K3 sidetone while making FLdigi cw timing adjustments https://github.com/x42/sisco.lv2