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Minidisc Player Diode?!

Helios

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I was thinking just now about the old portable minidisc player I bought some years back and how pitiful that technology seems today when I realized the unit burns discs!

Now mine could burn MUCH more information on a tiny disk than can be held on a CD so im curious as to what diode lays inside :thinking:

Anyone know anything about these? Im going to try and see if I can dig it up
 
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Helios

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Those make excellent concert recorders. Do you have a bilateral mic?
no and I cant seem to find it anyways. It was one heck of a device in its day even though so few people seemed to know about it. Way back when they were able to both play and burn up to a gig on 3" diameter disc!



on further investigation its seems that most (probably all) were 775-785nm as listed on the spec sheets I found so I am less upset about losing it.
 

Tech_Junkie

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I'm missing the mic too. You got my hopes up for a second. They are not easy to find, and when you do find one you pay for it.
 

Tech_Junkie

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1. Its small, and easy to hide.
2. Its digital, and gives you high quality audio if you have the right mics.
 

Helios

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interesting I did not know there were stereo mics for portable players
 

Tech_Junkie

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I found my in a trash pile. I cruse the rich towns on Saturday, and Sunday afternoon. They usually leave what they didnt sell at their yard sale on the side of the road. Mine was mint, in the box, with a pile of blank disks. No mic though.
 

aryntha

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Minidiscs don't actually hold more information than a CD.

There's two versions; Minidisc and Hi-MD.

Regular MD holds around ~250 megabytes, compared to CD's ~650 megabytes; and uses a 780nm (cd-style) laser and a magneto-optical head to enable recording. The way it gets more music onto the disc than CD is because it uses compression, similar to MP3 (ATRAC and ATRAC-3.) There are a few different compression settings the more modern ones can do, standard ATRAC v4 or v5 (~60-80 minutes per standard disc) or ATRAC-3 v1.0 or v2.0 (often called MD-LP) that can hold ~240 minutes per disc.

But because it's using compression, the actual data written to the disc is less, compared to CD's raw PCM.

The laser frequency and pit pitch on a standard minidisc is the same as that of CD; simply with reduced storage and compressed audio vs raw uncompressed linear PCM.

Hi-MD uses the same codecs (ATRAC/ATRAC-3) but uses a 650nm laser and DVD's pit-pitch to give approximately 1GB storage per disc, vs 250mb. Some Hi-MD recorders will allow you to record raw uncompressed PCM, like CD; giving you ~100 minutes of CD quality audio on a small disc.

So, think of it this way:

CD/PCM/780nm/650mb::MD/ATRAC/780nm/250mb
DVD/(lots of codecs)/650nm/4.7gb::HiMD/ATRAC or PCM/650mb/1.0gb.

Both use magneto optical recording; where the laser, similar to a CD burner, heats up a spot on the disc; but instead of the laser actually writing to the disc, a magnetic field is switched to change the polarity of the crystal structure. (versus something like CD-RW or DVD-RW which uses different temperature points for phase change and write.) So basically to be written to, the heat *and* magnetic field both have to be there. That means they're rather durable; as to erase such a disc, both the optical heating and magnetic field have to be present.

To read, however, all you need is the laser. MO discs (such as Minidisc) can hold archival data a lot longer than standard writeable/WORM or rewriteable optical discs. (This is less true with BD-R/BD-RE blu ray discs as they use inorganic dyes, vs CD-R and DVD-R's organic dyes; but MO still outlives them.)

It was actually a really cool technology but was too expensive too late.
 

Helios

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Ok yes mine was Hi-MD because all my discs are 1 gig. Is there any potential for that diode?
 

aryntha

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It'd be a "moderately" powered red (650nm.) 100mW maybe. Nothing to write home about. Minidisc usually ran at '1x'. Though magneto optical power requirements aren't the same as DVD-R requirements, at those speeds, it doesn't have to be very powerful to 'open up' the MO layer for a magnetic shift.
 




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