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floppies as analog audio media

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Mike Chambers

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not sure why i thought of this, but i had kind of an interesting idea. i was thinking about modifying a 3.5" floppy disk drive to record/play analog audio using floppies. as in, wiring the read/write heads directly to an audio source/output using regular RCA jacks.

the index pulse that the drive makes for each full rotation of the motor could be wired to automatically step the head to the next track. i don't think you could get too much recording time if the drive motor uses the normal 300 RPM, but if it's dropped down to say 25 RPM - should be able to fit a few minutes of sound.

this is possible, isn't it? anyway, it would let all of the old worn out floppies that are not reliable enough to store data anymore have a new purpose. :)
 
Dwight Elvey said:
Hi
Just needs a large bias signal added to the audio.
Dwight
Click to expand...

it does? i wonder how much would be appropriate. watching that video that linuxlove pasted, that overdriving effect is interesting. i suppose the signal can't be too strong if you want it to sound good. what sort of voltage does the floppy drive output to the head? any idea?
 
Silly people! The floppy disk was invented in 1946. By the 1950s, it had reached the low-end mass consumer market.

I laugh at "authorities" who claim that IBM invented the floppy disk. They didn't--they invented the digital floppy disk.

I'm surprised that Jeri wasn't aware of the analog technology.

If you want to goof around, consider lowering the speed of the drive to 50 RPM or so for more time.
 
of course, magnetic recording has been around for ages but i thought it would be fun to make something designed for binary storage do it instead of what it was intended to do. i might sacrifice a floppy drive this weekend and give it a go. yes, i really have that much time on my hands. could put it in a little makeshift case with some control buttons, a cheapo audio amp IC and/or and some RCA jacks.
 
Yeah, I've wondered about this myself - it's kind of a fun notion. A two-sided floppy should fit a total of (80 * 2 / RPM) minutes of sound, so that's 3.2 minutes a side at 25 RPM, or 6.4 total if you can play the sides seamlessly. (Wish I knew more about floppy drive hardware.)

It'd be amusing to pair up a microcontroller board with the mechanism from one of those USB floppy drives and have a portable audio player ;)
 
To avoid the index-step issue, you might investigate an Epson SD-320 3.5" drive. Instead of a stepper motor, this uses a voice-coil positioner in sort of a closed-loop servo. It should be possible to get a smooth spiral track on a drive with some tinkering.

Don't the early 650MB MO disks record using a spiral servo track, like a CD-ROM?
 
I know the Mitsumi Quickdisk format (used in the Famicom Disk System) was a spiral-groove approach (way to utterly negate the big advantage of disks over tape, guys...)
 
i found a floppy drive here at my shop i'm going to use for this. the PC interface circuitry is hosed on it, so it's a good candidate. i'll take it home tonight and give it some quality time with a multimeter and a power source to figure out which connection points do what i want. the motors will be easy enough to figure out of course, but the two heads each have a 5-wire ribbon cable going to them. i'll have to do some experimenting there.

i'm assuming the 5 wires would be for: ground, read +, read -, write +, write -? i've never messed with recording heads before, so that may be totally off..
 
Mike Chambers said:
it does? i wonder how much would be appropriate. watching that video that linuxlove pasted, that overdriving effect is interesting. i suppose the signal can't be too strong if you want it to sound good. what sort of voltage does the floppy drive output to the head? any idea?
Click to expand...

Hi
It needs to be strong enough that the audio signal modulates it. Even over driving a little
with the bias. It needs to be enough to overcome any magnetism so it need to
be quite large.
You'll also need to use deemphasis as well or the low frequencies will saturate.
Then play back will also need emphasis to restore the bass.
You could use the amps of a cheap cassette recorder. Most use a cheap magnet
to bias the tape. It is OK to do this, it just looses about 50% of the potential
dynamic range.
Dwight
 
Yeah, they're pretty much a total loss as far as useful media formats go. Even Nintendo only used them because they got a bargain on the drive mechanisms. The FDS was a nifty peripheral, but it could've been a hell of a lot better with a real disk drive.
 
commodorejohn said:
Yeah, they're pretty much a total loss as far as useful media formats go. Even Nintendo only used them because they got a bargain on the drive mechanisms. The FDS was a nifty peripheral, but it could've been a hell of a lot better with a real disk drive.
Click to expand...

Mine are on, respectively, a Smith Corona PWP word processor and a homebrew rig set up for reading and writing them. Pretty simple, just a data separator (9216) and a USART (2650). Does the job.
 
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