Do we have sample code on USB Headset application on KL series.
1. USB Audio Class Example for Headset application
2. Combine existing usb_speaker and usb_generator demo in KSDK USB stack
3. Expand the sample rate and bit depth to adapt to customer case
There is a complete USB headset solution integrated in the uTasker project, usable on all Kinetis devices with USB. Using ADC/DAC or PWM output (when no DAC available) or I2S based audio device (with asynchronous synchronisation for zero drift and proven in product operation).
Eg. http://www.utasker.com/kinetis/BLAZE_K22.html#AUDIO where it is combined with CMSIS FFT for spectrum and waveform display at the same time.
If you have a real requirement, tell me which KL part you use I can configure it so you can see it in operation on whatever board you have - configuration for custom HW on any chip usually takes about 10..15 minutes. For special audio processors the audio processor may need to be set up specifically so may not be possible without more details.