Diy BBD possible?

[amptramp]

Remember the early Xerox copiers with the rotating selenium drums?  These use a selenium-coated drum that is charged up to a high voltage then the image of a document is placed on them and lit up with visible light.  The light discharges the drum where it hits it and the charge left on the dark parts of the picture are carried onto toner that is printed onto the new page, making a copy.

We could use the same technology to load the selenium drum with a light level proportional to the audio voltage and pick it off with a capacitive sensor at a variable angle from where it is introduced.  We would not need the full width of a Xerox drum but with some width, we could use this as a delay for multiple independent channels.

Old Xerox machines must be cheap by now.