This is a tested working project. It will add stereo AY sound capability to your 48K ZX Spectrum.

A decent sound was missing from the ZX Spectrum computers until ZX Spectrum 128K was launched, which brought the use of AY-3-8910 three channel audio synthesis IC in games. Quite a number of games (not all) that were written for the 128K Spectrum could also run on the 48K but without the required AY sound chip, they ran silent. This board fixes that. If the game can run on a 48K Spectrum, it will find and use this card automatically, no mods to the 48K Spectrum is needed, just plug and play. (never plug this card, or any other peripheral to the ZX Spectrum when it is powered)

Although original ZX Spectrum 128K provided mono sound, this card will output a stereo sound thru a 3.5mm regular stereo earphone jack. You can connect any kind of amplified PC type speakers.

All the part numbers are clearly indicated on the PCB silk screen, SMD passives can be 0805 or 1206 size, pads are designed to accommodate both sizes, and suitable for hand soldering. Logic ICs are 74LS type, 74HCT types will most probably work too, but I wouldn't recommend using 74HC type, they don't play well with the TTL logic levels of the ZX Spectrum.

The board is tested with an original AY-3-8910 IC from Microchip as well as its Yamaha made clone YM2149. It should also work with the Taiwan made clone "File KC89C72" and some MCU/CPLD based modern replicas of the AY-3-8910

You can find a list of games that support AY sound and work on a 48K Spectrum here:

zxspectrum48.i-demo.pl/48K_AY_games.html