hello maybe sound crazy but i wanna make a cassette recorder .... i have some passions for ocult and paranormal activity and i wanna make a cassette recorder with arduino ... but somehow to can manipulating the frequency and the power of the head ... i wanna see if the voice of spirits can be recorded for real ... and after that i wanna try to researching and decode the sound in many ways even for hidden message. have somebody any ideea how can i make this ?
Start with researching how a tape head works.
If you are wanting to record audio, why tape? There are newer technologies available.
Weedpharma
I assume you want to modify a cassette recorder? Or, do you have a machine shop? About a million years ago I built the record/playback electronics for a cassette recorder, but I didn't build the mechanism.
but somehow to can manipulating the frequency and the power of the head ...
That sounds more like an analog project than a digital-hardware project. Changing the frequency of an audio signal can be done digitally but it's really beyond the processing power of the Arduino. In analog you can only change the frequency/pitch by changing the playback speed.
A recording amplifier (driving the recording head) has two "features". It applies [u]NAB Tape Equalization[/u] which boosts the highs and cuts the bass. (The complementary EQ curve is applied during playback.) It also mixes-in an ultrasonic [u]bias signal[/u].
It would be easier to record digitally with a computer. Then, you can manipulate/process/filter the digital recording in all kinds of ways with an audio editor. [u]Audacity[/u] is a popular, FREE, (open source) audio editor that can also record.
Audacity can also generate white or pink noise and people sometimes "hear voices" or other meaningful sounds in the noise.
If the tape noise is of any importance to this project, pink noise is similar to tape noise.
You could also "fake it", by mixing a faint audio signal (such as a voice) with a strong noise signal. It's also possible to bury a "subliminal" voice message down in the noise where it cannot be heard at all.
i wanna see if the voice of spirits can be recorded for real
Of course not! 
I'm a TOTAL skeptic... If "the spirits" want to speak to me, they should speak loudly and clearly so I don't have to use any tricks to hear them. And if they don't want to be heard, I doubt there are any tricks to hear them.
weedpharma:
Start with researching how a tape head works.If you are wanting to record audio, why tape? There are newer technologies available.
Weedpharma
because i readed about spirit ... ghost hunting and they say the spirit voice can be recorded on magnetic tape because are some kind electromagnetic fields
because i readed about spirit ... ghost hunting and they say the spirit voice can be recorded on magnetic tape because are some kind electromagnetic fields
An [u]inductor[/u] (coil) will pick-up magnetic fields and convert the magnetic energy to electrical energy, which can then be converted to sound (if the signal is in the audible frequency range). If you connect a coil in place of a microphone you can record magnetic fields digitally or with an analog recorder. Or, you can actually just use a length of (unshielded) wire. (The wire can be insulated, but don't use shielded audio cable which is designed to block electromagnetic interference.)
The main thing you'll hear is 50/60Hz power line hum because that's the strongest electromagnetic field around you. You can filter that out with a notch filter. Again, a notch filter is easy in an audio editor.
Or, you could try simply disconnecting the wires from the cassette recorder's head and let it pick-up electromagnetic signals without any other signal/sound, but the signal strength will be so small you won't record anything. The electromagnetic field will need to be amplified (electronically) before being sent to the record head.
Hoo haa, that's a good one! Unless the spirits are able to get themselves amplified and out to the recording head, I doubt you'll hear them. And if the spirits are strong enough to go right to tape, what is to keep the whole tape from picking up the same thing at any one time? In which case the only heard will be the last warble made while in the vicinity.
There is only one spirit I believe in and it comes in a bottle. 
Weedpharma
weedpharma:
There is only one spirit I believe in and it comes in a bottle.Weedpharma
Not the one I had in mind but I am willing to compromise.
Weedpharma
jacoblast:
because i readed about spirit ... ghost hunting and they say the spirit voice can be recorded on magnetic tape because are some kind electromagnetic fields
If one accepts that such things can only be recorded on magnetic tape, one could still copy the audio to digital (via a sound card) and do fast/slow/reverse/frequency shifted playback using the wealth of available PC based audio processing tools.
weedpharma:
There is only one spirit I believe in and it comes in a bottle.
There are several different spirits that come in bottles, no belief needed.
Henry_Best:
There are several different spirits that come in bottles, no belief needed.
I believe that the spirit of that dead worm is very real and evil
too many time he has made me sick.
Delta_G:
With this beautiful spirit, Id rather use a video tape.
jacoblast:
hello maybe sound crazy but i wanna make a cassette recorder .... i have some passions for ocult and paranormal activity and i wanna make a cassette recorder with arduino ... but somehow to can manipulating the frequency and the power of the head ... i wanna see if the voice of spirits can be recorded for real ... and after that i wanna try to researching and decode the sound in many ways even for hidden message. have somebody any ideea how can i make this ?
you should be able to buy a casset tape recorder. check flea markets
tape should not be needed.
the microphone is the primary element.
record to an SD card and then you should be able to compare sounds.
dave-in-nj:
I believe that the spirit of that dead worm is very real and evil
too many time he has made me sick.
Not as sick as Spirits of salt would make you.