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Comment by anfractuosity | Hacker News Reader

I assume this is the project you mean? - https://ofersp.github.io/digital_needle/ it's a shame there doesn't seem to be sourcecode. Very cool though.

You can also get laser turntables - https://en.wikipedia.org/wiki/Laser_turntable which look intriguing

I'm rather curious about these microscopes - https://matesy.de/en/products/magnetic-field-visualization/m... which can visualise magnetic fields, they're very expensive though.

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If I remember correctly, laser turntables were not popular because they also reproduced all the fine dust on the surface of the disk.

Yep. Every tiny dust particle makes an audible pop, while an actual stylus would've just pushed it out of the groove.

So laser turntable needs a leading 'dust plow' ?

That sounds good! Two other solutions:

- low pass filter. Assuming the dust is small compared to the expected movement in the groove, you can filter it out electornically.

- dust detector. Nikon had a cool 35mm scanner... instead of RGB, it had an additional IR layer at an angle just to detect dust. So, automated dust removal tools knew if a black spot in an image was supposed to be there, or if it was actually dust. Here, extra optics would know if the laser was reading dust and could mute/filter the sound during that time.

Interesting ideas!

The 'dust detector' is 'Digtal ICE' that you'll sometimes see labeled on scanners. (https://en.wikipedia.org/wiki/Digital_ICE)

Someone should try doing a dsp+ml hybrid filter that takes both the optical signal and the generated audio into account to filter out the crackling

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