Sinclair ZX80 / ZX81 / Z88 Forums

updated the above picture.

You are right, the didaktik M is a spectrum clone, not a ZX80 or ZX8 clone, in the didaktik series there is no ZX81 clone. the best, most complete, "list" I could find about ZX81 clones is in the Czechoslovakian wikipedia page here: https://cs.wikipedia.org/wiki/Klony_po%C4%8D%C3%ADta%C4%8D%C5%AF_ZX...

by the way, the very first clone of a ZX-class Sinclair computer was the MicroAce which came out in the USA just months after the ZX80 was launched in the UK, and was clearly a direct copy of the ZX80, even including the original ROM, it later became licensed, but originally it was simply a pirated ...

old cassette players gave out a lot more volume than sound cards of PC do.
Try to output as much signal as possible (try finding mixer options that limit the output level).
My clone has a special input circuit to compensate for the expected lower input level.

a few more, two from the east block, one from china: didactic from Czechoslovakia. P.S. This is actually a spectrum clone, look closely at the top row of keys and you can just make out it lists colours. Didactic ZX81 clone.jpg CZ 1500plus, also from Czechoslovaki. CZ 1500plus in Box.jpg laser 110, f...

Here is the finished and optimized PCB Layout of the PSG expansion board for my ZX81+35:

after a long layout session on the ZX81+35, with which I corrected an error in the expansion port layout I have continued with the schematic and layout of the PSG expansion board for my ZX81 clone:
this is the current schematic:

ZX81+35 revision 4.0 layout is finished. Still have to solve the image stability when running in turbo mode, (another issue, AFAIK the only one remaining) but I have some ideas for a fix. Also, I will now return to work on the PSG board, with a correct edge connector orientation. This is the new lay...

this project was delayed when I found out a mistake in my original ZX81+35 design, in that the edge connector was mirrored when I transposed the edge connector from the top of the PCB to the left side I made a mistake, and pin 1 should be on the bottom (toward the keyboard) but its at the top, So I ...

So here its is, a redesign adding multiple PSG board support, and also support for use with other boards that use address lines as (active low) "chip selects" on A4, A5 or A6. PSG for ZX81+35 REV 1.5.png Note; I also implemented a "audio interconnect" header to mix sound from the second board with t...