A few short news:

1. Since the beginning of the project, I thought it was impossible to use the Raspberry Pi's built-in audio chip, because it always led to stuttering sound. This is wrong, I've now been able to make SamplerBox work with the Raspberry Pi's internal sound chip. Thus, a USB DAC is no longer mandatory. It is still recommanded for better audio quality, but not mandatory. More news about this in a future update!
   _{^{Technical reason: I replaced pyaudio (which has some bugs somewhere, note: this is not the first bug I discover in this library, there's also one leading to crashes on Winows platform, when devicenames use non-standard characters such as é or à!) by the module python-sounddevice, which is equivalent (a python wrapper for PortAudio) but cleaner.}}

2. A RaspberryPi 3 ready-to-use ISO image is now available here.