Another SD storage solution for PET computers.

Seeing this made me wonder if anyone had ever attempted or succeeded in making an "SD to IEEE-488" type device for the PET series? I used to run a lot of IEEE drives with my SuperPET 9000 and C64 with a Buscard ][ when I was building my BBS on Image 1.2a. At that time anyway, software like Image really didn't work with things like the Epyx Fastload cartridge and I had tried almost half a dozen different IEEE interfaces made for the C64 but the Buscard was the most compatible with the most software (including Image) so it won the day. I was never able to afford JiffyDOS, and by that time had invested so heavily in IEEE drives that it wouldn't have made much of a difference anyway because I only used one 1541 on the board for booting it and as a UX exchange. To my mind, IEEE would have been much faster than tape loading anything into a PET, but maybe that was more a limitation on the cassette medium and not so much the tape interface itself, though looking at that circuit diagram it looks like he is just switching 5v / gnd to the cassette read pin and the write pin from the cassette port drives a transistor to ground against a 3.3v pullup so this would clearly be a straight 1 bit at a time connection. Actually, thinking about this raises another question; If you are toggling a data line between 5v and ground when "writing" to a dataset, presumably the dataset must modulate a tone to be recorded onto the magnetic tape in order to record it as audio, would it not? Or does it just literally pull the magnetic head between 5v and GND and the resulting magnetic "pattern" that produces on the tape is enough to distinguish a 1 bit from a 0 bit? I've never really thought about it but I kind of assumed it worked somewhat like a modem, generating two tones - one to represent a one and the other to represent a zero, because I remember listening to dataset tapes on a Hifi stereo and they sound awful! haha But to my aging memory it did sound somewhat resembling that noise of a modem, if not quite so "static-y" sounding and more tonic? If that makes sense? Hmmm.