Magnetic reader

thanks a lot for the reply, in this project I've to use a magnetic head, not a pre-built reader so I'll have no clock data but that on the track itself, the encoding that I'll be dealing with (when I'm able to retrieve the F2F signal and the binary from that) is the ABA of the middle track of a credit card, however I've assemble the circuits on this forum and the one of this application note:
http://www.eettaiwan.com/ARTICLES/2001OCT/PDF/2001OCT04_AMD_CT_AN2112.PDF
However with both I'm having problems, the first (the one on this forum) the output changes from 0 to 1 even though I'm not swiping and when I pass the card it does nothing, the second one stays low all the time, and the voltages that I get are not the ones for the stable state presented in the app note, but I've built it three times from scratch with the same result every time
My magnetic head is working 'cause if I swipe it i can see the signal after amplification, however I'm unable to transform that signal to a F2F encoded wave :frowning:

any help??

thanks a lot