A few years ago, I adapted the TZXduino project to work to create master tapes for The Future Was 8 bit cassette range, creating something out of a spare Spectrum +2 case, using it's tape deck to record the tapes.
That turned out to be quite useful, so I ended up fitting the prototype bits into a second spare +2 case to make one for me.
That's been handy a few times, but every time I dig it out, I have to fiddle around a bit as it's still on a breadboard and the switches keep popping out.
I had also used an Arduino Ethernet board because it had an on board microSD card, but was missing the USB serial on board programmer. The last time I dragged it I decided to do it properly. The case was still fine, it was a +2 where the keyboard supports had all been snapped by shipping it with the powersupply sitting on the keyboard.
I went for a standard Arduino UNO, so that it could be powered and programmed via USB. I wired up an Arduino portotype shield with the buttons and connections.
As I wasn't using the Ardunio Ethernet any more, I needed a card reader. Here I used an SD2BBC board, which was adapted to work as a plain card reader.
The final element was the display, here I reused the original one, as that was working fine.
And it is complete. The white plug in the middle is the output to the cassette deck built into the Spectrum +2 case.
I used that to generate the tapes I needed.
A minor modification requested by TFW8b was to create multiple copies, so I added the number of copies required to the menu, used to create multiple copies of the same program on each tape.
I've been getting mixed results from loading vintage ZX81 tapes into the Minstrel 3, some of them have not stood the test of time well, with noise and dropout.
I didn't fair any better loading them into original ZX81 hardware.
I got better results on both from the newly created tapes.
I made up an alternate lead for the TXZduino, with a 3,5mm jack plug on the end, to drive the ear input of the ZX81 / Minstrel 3.
That worked fine, and I have been using that for the cassette loading testing.
That works much better, cutting out the analogue tape middleman.