One of the first difficulties I had with my K2 when I wanted to go digital was a constant-level audio.
Problem: If I ran the audio from the speaker or headphone jack, when I adjusted the AF control for comfortable listening, it changed my waterfall.
Solution: I needed a constant-level audio that didn’t change. There’s a “line-out” available as Aux AF at J5 on the K2’s RF board. It’s near the front center, and should be 3 empty holes without a connector. It’s the output from the product detector, which should be adequate for most audio uses.
What I did: I connected a small 8″ stereo wire from J5 to a 3.5 mm stereo jack (Elecraft E620027) mounted in an empty hole on the back of the K2.
Wiring in photos above: P5-1 = Ring (black), P5-2 = Ground (shield), P5-3 = Tip (red)