getting to know your read/write heads

Re: getting to know your read/write heads

Postby cosmochaos » Mon Jun 06, 2011 5:23 am

Hello,

i am not familiar with the electronics but based on the post of this forum I achieved to control the spepper (using an arduino board) and to spin the motor! Now i want to read from and write on the floppy disk. I wired the floppy head but I don't know which of 5 wire wires are going where! I am waiting for your reply!
(Sorry for my bad english)

Thank you
dimitris
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Re: getting to know your read/write heads

Postby mcanulty » Tue Jun 07, 2011 9:37 pm

Hi Dimitri, you can try to follow the diagrams in the earlier post in this category, or you can just pick two and give it a shot. I'd say pick two of the inner ones and you should have a good chance to being able to read and write. Let me know how it turns out!
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Re: getting to know your read/write heads

Postby cosmochaos » Tue Jun 14, 2011 6:46 am

Dear Dan,

Thank you very much for your reply.
I recorded on floppy by mistake! I can playback the recorded data using 2 and 3 wires.
Do I have to use the same wires for recording?
I would like to use it with a guitar.
Any ideas of how can I improve the sound quality?

Thank you again,
dimitris
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Re: getting to know your read/write heads

Postby mcanulty » Tue Jun 14, 2011 11:57 pm

So far I've had to use the same wires, so I set up a system with multiplexers and stuff to use three different drives. If I find a better method I will write about it! As far as audio quality, you can always try changing the loudness of how you write it, maybe more loud or less loud is better. And for reading off, I made my own amplifier system, and I'm thinking of trying a new system for the next version though that might get rid of the RF interference.
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Re: getting to know your read/write heads

Postby mitcho » Wed Sep 07, 2011 6:02 pm

Hello!
I need some help to get the audio signal recorded on the floppy. I drive the audio signal directly into the r/w head through the 2. and 3. wire and also tried with the 1. and 2. on another floppy drive. I chose those because they have the lowest resistance in between (4ohm - 14ohm), similar to the resistance of the speaker (8ohm) of the amplifier that I use to drive the signal. I tried with a low signal and slowly raised the loudness throughout the recording. When I read from the head I connect the same wires from the r/w head to my PC's mic input and boost it as much as I can, but nothing but noise comes out. I noticed that since I've soldered the wires on the r/w head between the 5th wire, the one that should go to GND, and the others there's around 140K ohm of resistance instead of infinite. I don't think this should be the problem. What should I try now?
Thanks a lot for this forum and all the information you're providing.
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Re: getting to know your read/write heads

Postby mitcho » Thu Sep 08, 2011 1:17 pm

Hi, here's the schematics of what I did. Could anyone please tell me what I did wrong?
I even measured the voltage out of PIN 2 and 3 from the r/w head and there's nothing...
Thank you!
Image
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Re: getting to know your read/write heads

Postby guest » Thu Sep 08, 2011 1:54 pm

i dont know too much about the floppy audio
but maybe the signal is very low
and the computer can not amplify it enough

if you have a phono amplifier
give that a try

also check that the head still has the same resistance
its posible the coil got burnt out
if your amp drove it too hard
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Re: getting to know your read/write heads

Postby mitcho » Thu Sep 08, 2011 6:53 pm

Yes! I tried with the phono preamp and I'm beginning to hear something... still very low and in a buzzy noise, but enough to motivate me to go on. Seems like I have to find proper cables or ground better the ones I'm using. The noise is lower when I take the cable in my hand.
I found the max loudness to record before the signal gets distorted. While testing I drove it a lot and heard the distortion in the playback. The head still works, so the r/w head isn't that fragile.
What preamp are you using? If I can't get rid of the noise I'll try to find a preamp of the tape recorder.
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Re: getting to know your read/write heads

Postby guest » Thu Sep 08, 2011 11:20 pm

the phono preamp should have a ground point
if you are not using it yet
you should connect a cable from that
to the case of the read head
which is most likely ground of the whole thing

i havent built one of these myself
so im not speaking from experience
but i think dan may have used a microphone amp
on a mixing board
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Re: getting to know your read/write heads

Postby mcanulty » Fri Sep 09, 2011 12:32 am

Yeah this is all exactly correct it's what I would have recommended as well. I found I had to drive the r/w head fairly loudly, although I was always hesitant as I didn't want to burn it out, but the only time I burnt a head out I had accidentally run DC through it instead of something AC like the output of an amplifier. I wouldn't worry too much about 4 ohms vs 14 ohms, in fact maybe the 14 ohms side would work better, it's worth a shot.

The computer amplifier might not have been powerful enough, the phono amplifier is a much better thing to try, I also had a lot of early luck taking a tape head amplifier, basically taking the wires that normally connect to the tape head on a tape player, and instead running them to the floppy head. Then I hit play on the tape player and listened back to it. It's a little better than a phono amp, but they're very similar, so they ought to perform similarly. The signal coming out of the r/w head is very very small, so you might not see it if you are looking at it without amplification.

Now, on getting rid of the buzzing, there's a lot of black magic involved. Sometimes connecting the shield line on the head with the ground of the amplification circuit helps, sometimes disconnecting them helps. But play around with it, you can get relatively clean signals, and it will be a blast when you do! I remember the elation I felt when I heard the sound coming through after bashing my head against this for so long, it was totally worth it.

If you're using a tape player for your amplifier, a lot of times the tape head has a shield line connected to it (like a bare wire normally), this is what I connected to the shield of the floppy drive. It also matters how long your wires without a shield are. If you think of the shield as a little faraday cage around everything that you care about, then where it is broken you will get noise from the outside world into your audio lines. Since the signal off the magnetic media is so so quiet, all of that noise from the outside world creeps in. So the fewer opportunities for noise to invade your audio wires before the amplification happens, the cleaner your sounds should (hopefully!) be. As far as writing the signal goes, you don't have to worry too much about shielding there because your write signal is waaay louder than the noise being picked up on the wires, so its effect will be negligible. Readback though is very sensitive, so that's where you get to learn the most about shielding and stuff like that.

Thanks for posting your schematic, it really looks like you are on exactly the right track!
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