Hi, I encountered this strange behavior when running fl2k_test on Windows 7: basically after a while the sample rate drifts and speeds up considerably. Sometimes it even starts up directly like that. In the command prompt I get: C:\Users\Francesco Gugliuzza\Downloads\Sviluppo\FL2000fl2k_win_2018-08-09>fl2k_test.exe -s 138e6 Reporting PPM error measurement every 10 seconds... Press ^C after a few minutes. real sample rate: 146656386 current PPM: 62727 cumulative PPM: 62727 real sample rate: 150803676 current PPM: 92780 cumulative PPM: 77858 real sample rate: 149716182 current PPM: 84900 cumulative PPM: 80218 real sample rate: 150107883 current PPM: 87738 cumulative PPM: 82104 real sample rate: 150526750 current PPM: 90774 cumulative PPM: 83843 The same thing happens if I compile the latest osmo-fl2k myself using Cygwin. I'm running everything on a laptop with an i7 4710HQ CPU and 8 GB of ram, and I'm using a RayCue HDMI+VGA box. Do you have an idea why the real sample rate drifts so much? Thanks! Francesco -- Francesco Gugliuzza M.Sc. in Computer Engineering Ph.D. Student at DIID, Università degli Studi di Palermo Qualified to practice as a Professional Engineer E-mail: fgugliuzza.mail(a)gmail.com PEC: francesco.gugliuzza(a)pec.it