I needed a method of easily loading games for the ZX81 and buying original cassettes wasn’t really on the cards. Normally I look for some sort of native SD Card solution and even though one exists for the ZX81 (ZXpand), it wasn’t easily available to purchase and was probably a bit overkill for my needs.
So instead I went for a slightly different method, and although it is still SD card based, this unit actually reads TZX files from the SD card and then plays them back as sound files out the headphone jack.
The obvious disadvantage is games load at the same speed as they did from tape. But the advantage is this unit is compatible with many of the older computers that used tape as their medium.
It’s actually a really nice little device and since the games for the ZX81 were quite small anyway, they don’t actually take that long to load. 1K Chess for example took about 30 seconds (An entire Chess game fitted within 1K of memory, crazy!)
I purchased this unit from eBay for £24, but you can find them in various different shapes and sizes. I’ve even seen a project where someone built one into an empty cassette tape.