La scheda madre è una asus b450 prime plus.
Visto che le caratteristiche di conversione ADC della tua scheda madre sono buone direi di utilizzare la presa microfono di essa per il segnale BF-out che proviene dal ricevitore:
Caratteristiche del chip codec audio della tua scheda madre ALC887 V2:
Hardware Features
DACs with 97dB signal-to-noise ratio(A-weighting)
ADCs with 90dB signal-to-noise ration (A-weighting).
Meets Microsoft WLP3.x (Windows Logo Program) audio requirements
Eight DAC channels support 16/20/24-bit PCM format for 7.1 sound playback
Two stereo ADCs support 16/20/24-bit PCM format, multiple stereo recording
All DACs supports 44.1k/48k/96k/192kHz sample rate
All ADCs supports 44.1k/48k/96k/192kHz sample rate
Primary 16/20/24-bit S/PDIF-OUT supports 32k/44.1k/48k/88.2k/96k/192kHz sample rate
Secondary 16/20/24-bit S/PDIF-OUT supports 32k/44.1k/48k/88.2k/96k/192kHz sample rate