[crazygringo]

> it seems intuitively obvious to me... you can encode "more" data in an analog way than digital

It doesn't seem obvious to me, because I'm not talking about encoding distinct symbols into the medium. I'm talking about using the entire available frequency range to encode digital information the way a modem does. And I'm talking about using lossless compression as well. And as you say, if an LP can encode ultrasonic information, that opens up all sorts of extra space for information that is useless in analog.

It may very well be the case that an LP couldn't record CD-quality audio, but I do very much wonder what kind of bitrate would actually be achievable. A dial-up modem is 56 kbps, using the frequency range 300 hZ to 3.3 kHz. CD audio is 1,411 kbps, but vinyl frequency range is from 7 hZ to 50 kHz, which is 16x wider than a dial-up modem. And you can pack much more data into higher frequencies.

So on the face of it, digital CD-quality audio seems like it might be very much achievable in theory on vinyl. But again, when you account for error correction and degradation and particularly distortion, I wonder if you could actually get it reliably in practice.

[dweymouth]

Hmm that's a good point, that you can use the ultrasonic bandwidth of the LP, which is useless for analog audio, to increase the bitrate. I'd say it's a bit generous to give an LP a bandwidth of 50 kHz, especially in the inner tracks though. I think what I was getting at would apply where the bandwidth of the analog signal you want to encode is as wide as the bandwidth of your media though. Take compact cassettes, let's say they have a bandwidth of 18 kHz and a dynamic range of 60 dB. If you want to encode an arbitrary audio signal with a bandwidth of 18 kHz and with 60 dB dynamic range, you could only do that in the usual analog way. But if you wanted to encode a digital telephone signal (say at 8 kHz bandwidth, 30 dB dynamic range) maybe you could use the 18 kHz cassette bandwidth to encode that signal digitally.