Melodik2 AY Interface

This is AY interface based on Melodik from Didaktik Skalica, newly designed by me. It fits to original Melodik case, so you can replace old Melodik PCB with this one. What is new? Logic was enhanced to avoid collision with D40/D80 FDD interfaces, ACB stereo mixer was made by golden ratio principle, clock for AY chip is crystal driven, audio loop-through for Didaktik Kompakt users, power supply for AY chip is filtered for crystal clear sound and I/O gate was bring out to pihneader.

Part list:

1 x AY-3-8912
1 x 74LS00
1 x 74LS02
1 x 74LS74
1 x 74LS138
1 x 100uH / 185mA / 3.5 Ohm inductor
1 x 15R resistor
5 x 470R resistor
2 x 1k resistor
2 x 1k6 resistor
2 x 8k2 resistor
1 x 4k7 potentiometer
1 x 1n ceramic condensador
1 x 47n ceramic condensador
7 x 100nF ceramic condensator
2 x 4,7uF electrolytic condensator
1 x 100uF electrolytic condensator
1 x 220uF electrolytic condensator
1 x 3.57954 MHz crystal
1 x LM386 amplifier
1 x 75R speaker (if you don't have original one), or 8R speaker + 68R compensation resistor
1 x 1x2 pinheader
1 x 1x10 pinheader
1 x slot56 connector modified to ZXS system bus

Download PCB gerber files - 2017 version or 2015 version, both tested with ZXS Spectrum issue3b, issue4a, ZX Spectrum+ issue 6a, Harlequin 48k Rev.f, Didaktik Gama '89, Didaktik M '91, Didaktik M '92 and Timex 2048. Nevertheless I can't guarantee absolute perfection, because I do not have any test equipment and keep in mind, this is hobby project only.

I made also new case which is printable on 3D printer - grab STL files here. PLA material is recommended. The case size respects ZX Spectrum+ dimesions, but it fits nicely with other computers (except Didaktik M because of its case shape).

Pictures:

Schematic.

PCB top layer.

PCB bottom layer.

Ready to use.