I have several types of Raspberry Pi boards. The Raspberry Pi board is probably one of the most sold boards in recent years. Raspberry Pi boards are inexpensive and have great performance. The best thing is that you can use Linux. The figure below is a collection of RPI V1 to V4. It is RPI V1 The board on the right in the photo below is a recent RPI V4. Already, amateur radios are using a variety of Raspberry Pi boards. I am trying to make something new. For example, network radios for amateur radio, Devices using Wsjt-x I experimented with cheap USB sound cards for the new project. All are USB sound cards under $4. The sound quality was all poor. However, the RPI's fast CPU will enable DSP functionality. Below is a $2 USB sound card with a cable attached to it. All are compatible with RPI. Below, I thought it was possible to input a 2CH microphone with a $4 USB sound card. However, it was only 1CH microphone input. The first project