8BIT Wave is a project I started in order to build a digital cassette deck for my old 8-bit retro computers, my starting point was the schematic provided as part of the DigiWavuino project by Ricky ElQasem though it's more or less grown towards being its own thing since then. Later versions also support the Maxduino-firmware (includes tzxduino and arduitape functionality), that way I can use it with most - if not all of my vintage computers using one device (refer to maxduino documentation). Anyway, enough of all that - here is a picture of the device loading a game on ZX Spectrum: