check this out, a use for all those cassette walkmans found in thrift stores and garage sales:
http://brokenpants.com/?page_id=211
this one i just made, quite easily... i find it perfect to use in conjunction with a contact microphone, suprisingly it creates a nice heavy and pretty useful distortion i suggest trying to keep the volume knob intact on the walkman when doing this project, as it is useful tool in manipulating the volume level (because to me this thing is LOUD at max volume). it also does some changes in tone when there is heavy feedback, awesomely loud when plugged into my fender twin tube amp. the key is to connect a wire between the one channel of the headphone output to the contact point for the right channel (or ring) of the input jack, this allows an internal loop to occur and the input signal to go through twice creating double the distortion... i haven't done it but it was mentioned in that link that adding a spdt/spst switch between these contacts will allow for switchable less and more distortion which may also be handy. disconnect the connections to the spring mechanism that operates the tape player functions (play, f. forward, rew., stop) and put a spdt/spst switch so you can easily turn on and off the circuit, a useful kill switch.
p.s. there is also a link on the above page about making a contact mic. though its not the most recommended way of doing it (i highly recommend removing those super flimsy wires connect directly to the piezo and solder the contacts of your new wire to the piezo disc and then using a hot glue gun, add glue to keep the contact joints attached, that will make it much more durable and less likely to break in mid use, whcih is very annoying)
this is the next project:
http://ofsoundmind.wordpress.com/200...ing-a-walkman/