With respect to the first approach, I briefly explored two of the available Raspberry Pi add-on audio boards: If you want better audio quality or need to record an external audio signal, there are two approaches: Raspberry Pi 2 does not have an audio input. Ideally, the speaker should be completely silent. I can hear a loud hiss from my speakers when JACK is running and sending audio through the built-in DAC circuit. JACK seems to modify the audio sample stream as well. (This latter point alone is subject to debate!) There is much on-line debate about further improvements, but the PWM technique seems is limited by the 11-bit quantization. Later RPi models (like the B+ and generation 2) have better power regulation and produce less digital noise at the audio output. The software performs RPDF dithering and noise shaping to improve quality. The PWM technique produces OK audio, but not good, clean audio. Click on images to enlarge and get full resolution.) The Raspberry Pi drives a pulse width modulated (PWM) signal into a passive low pass audio filter. However, Adafruit (and others) claim that the audio circuit is the same as the earlier, first generation Raspberry Pi. The Raspberry Pi Foundation has not yet published a schematic for the Raspberry Pi 2. Finally, I describe my experience bringing up the Behringer UCA-202 USB audio interface on RPi2 and Raspbian JESSIE. Then, I briefly mention a few alternative approaches for high quality audio output and audio input. This article starts with background information about the built-in audio circuit and why it is lo-fi. If you tried this with your own RPi2, you realize that the sound quality is good enough for initial experiments, but not good enough for production - unless you’re into lo-fi. We used the built-in, 3.5mm audio output from the Raspberry Pi 2 (RPi2) to produce sound through powered monitors. Raspberry Pi soft synthesizer: Get started Get started with Raspbian Jessie and RPi2 In the first few articles of this series:
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