There are a number of ways to do it. I was mainly limiting my initial experimentation to 'junk box' parts at this point and then maybe if things work out well I'll do some actual engineering The TIP-125 came to mind as you can drive it with a PN2222 and not have any issues switching a higher voltage than your logic voltage. The component cost is also low. A 1A~2A logic level mostfet would also fit the bill. There is something in the back of my mind about using them to switch a higher voltage than the logic voltage though, I'll have to think on that some more.

While a bit late to the party here, I can't help but think that using one of the portable "walkman" style MiniDisc recorder/players could be a nice fit for using the old cassette interface. The frequency response, distortion, wow/flutter are all far better than the typical cassette machine. The audio in/out would be the same... just that the remote control would need to be changed.

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Regards, KM
https://github.com/floobydust

It would be worth trying, but beware: it's not a linear format:
https://en.wikipedia.org/wiki/MiniDisc# ... ompression
unless it's 2004 or later, using Hi-MD format:
http://www.minidisc.org/hi-md_faq.html#_q87