hello @phil, there are several versions of SamplerBox, all of them based on John’s first one.
I recommend you to use this one: http://homspace.xs4all.nl/homspace/samplerbox/ as Hans is continuously working on it and doing improvements.
I am running it on a Rpi3B with Pisound. You will have to disable ALSA mixer / GPIO / serialport midi. Another important thing already said in this thread is that you will have to adjust SamplerBox to work at 48kHz. Change the samplerate in the code.
Give it a try and ask me if you have any question.