Hi All
The following article on Wikipedia gives some information on how the 1530 Datasette worked:
https://en.wikipedia.org/wiki/Commodore_DatasetteSome detail is given on how the analog data on cassette was converted to digital data with which the Commodore 64 could work with.
However some brief mention is also made that when recording data to cassette, the 1530 also contained an audio filter for converting digital data to analog:
Quote:
The Datasette has built-in analog to digital converters and audio filters to convert the computer's digital data into analog sound and vice versa
I could not get much information on the Internet on how this audio filter worked which was harnessed during recording, except a schematic from the zimmers.net website, which I have attached to this post for reference.
On the above mentioned schematic I it looks some kind of audio filter was implemented indeed during the recording process. However, I didn't had any luck figuring out how this filter works.
Can anyone perhaps give an explanation on how this filter works, or give some pointers into the right direction?
Once I have figured out how this filter works, I thought it would be an interesting exercise to implement this filter as a digital filter on an FPGA and take any *.TAP file and see if you can recreate the original sound as heard when you would play the original tape on a tape deck.