Dave.. .just noticed that your callsign mirrors your initials.. way cool.... Yes, I have Built-In Input selected .. and yes, I see the bar-graph responding the audio out from the KX3.. I have been keeping it on low side.. midway and below... is that a mistake? I am able to delve deeper into the MBP - navigating to Applications / Utilities / Midi sound .. where I can open sub menu and further adjust the attenuation / boost of the input signal. Yes, Built In Input is selected in FLdigi as well. On the KX3 - I am using the Phones output with the level set at around 25 .. .on a scale of 0 to 60. As aforementioned I have tended to keep the audio down around the mid level and lower.. as you say .. I should look at boosting this up some either on the radio or some radio and some on the MBP so that the bar graphs comes up to around the 75% area. Squelch level on FLdigi is very close to the bottom .. I will move it to the bottom.. until I start getting something decoded . .and will tweak from there.. Yeah... I think that you have homed in on the most likely cause... audio level too low! .... I have been over cautious in that regard... will boost and report back. thank you, so much, Dave for walking down this path with me... I appreciate you. God bless, - David KM4QVM, Macon Ga.