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Vinyl records, as well as 78s (with the exception of a very few, and incompatible, records from the very first years), have a V-formed track where the stylus rides. On a stereo record, the sound from the left channel is engraved in the 'hillside' that is the one arm of the V, the right channel sound is engraved in the opposite V arm hillside.
The question: How is the sound 'encoded'?
If the sound in both channels is identical, like mono sound (or the source located exactly midway between the microphones), do the hillsides then move out to each side, and come in from both sides, in identical moves? If so, the bottom of the V, the valley between the hillsides, forms a straight line, but moving up and down, and so does the stylus tip.
Or, do the two hillsides move in parallel to the same side and back again, 'holding hands'? Then the stylus tip moves from side to side, but not up and down?
On a 'true' monophonic record, the V track goes from side to side, with constant depth, suggesting that for a stereo record, the second alternative is the right one, but I am far from 100% sure about that.
Can anyone tell, with absolute certainty, which alternative is right for a stereo record? Does the stylus tip go in a straight line, but up and down, or from side to side, but at the same vertical depth, when a stereo record plays exactly the same sound in both speakers?
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It's left/right encoded: How stereo phonograph records work
About 2/3 of the way down the article there's a highlighted photo showing different frequencies on left and right channels.
Keep Calm and Carry On
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Very cool - never gave it much thought before. Just yesterday I brought a couple Weather Report albums circa 1970's up from the basement to play this week. 
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Craig Robbins wrote: Weather Report albums
Guess what I'm going to listen to when I get home?
"the debugger doesn't tell me anything because this code compiles just fine" - random QA comment
"Facebook is where you tell lies to your friends. Twitter is where you tell the truth to strangers." - chriselst
"I don't drink any more... then again, I don't drink any less." - Mike Mullikins uncle
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I had the Heavy Weather album, hat with lightning on the sleeve. Favorite tune, "Birdland". Just looked it up, it's the Indiana Jones Fedora!
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Yep, first track on side 1. My favorite tune of theirs as well. I turn up the volume for that one. Their albums have great cover art.
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When I was a boy, in the 1970, our neighbor shipped some old, worn records across the pond to have them photographically read/restored - he got the results as an open-reel magnetic tape. Today, I am quite sure that must have been 78rpm records - I very much doubt that the technology of the 1970s was good enough to do it on 'microgroove' vinyl records. He was very satisfied with the results, claiming to hear instruments (he specifically mentioned triangles) that he had never heard from the mechanical record. The stylus rides down in track, not touching the edges between the 'land' and 'valley' surface areas, so these edges are not worn with use. In stray light almost parallel to the surface let the original, the original, unworn edge could be read with an optical pickup, as the borderline between the lit land and the dark, shadowed valley.
I was considering if a similar technique would be possible on 'modern', stereo vinyl records. Some simple back-of-envelope calculations did tell me that it is not a project for your hobby workshop in your basement.
Say that you use a microscope with an image area 0.2 to 0.1 mm wide - vinyl grooves are typically packed 7.5/mm, on some records up to 10/mm. Assume the microscope ocular is a high-res 8K video sensor. Since the image must capture both sides of the groove (on a stereo record), there are 4K pixels to each side. This is to capture the amplitude of the signal: 12 bits of resolution at the very most. More like 11 bits on the average. Maybe you can steal an extra bit of resolution by looking at the bit on the edge: is it almost white, light gray, middle gray, dark gray, almost black?
What about the microscope optics? Can it, for an image area, 0.1 mm wide, provide a resolution of 8K pixels? That is pixel width of approx. 0.01 - 0.02 µm on the record surface. The traditional resolution measures, such as line pairs/mm is not directly transferable to sensor pixels, and I am by no means an expert in the field anyway, but from what I read about microscopes, that is significantly beyond the capabilities of traditional optical ones. The wavelength of the light limits the resolution. Maybe you can get closer by using short-wave UV?
... What fascinates me is that what I want to read out are no smaller details than the pickup stylus manages to read out! From a top quality, factory new vinyl record, it can deliver at least 60 dB S/N. That sure isn't more than 10 bits, but it does it almost without any effort. Why should it be so much more difficult to trace the edge optically than with a needle?
So I cannot let go the idea of reading the edges of the groove optically, as well as the simple mechanical stylus does it. Hoping that there will be some way of doing it, the next step is how to decode the waving edge forms to proper music. Even if we call it 'analog', it isn't as identical to the sound waves as we are led to believe; you need do correct for various curvature of the grove, various linear speed, separate the stereo channels, do proper de-emphasis, and then noise removal which might benefit a lot from the direct microscope images to identify e.g. dust particles ...
At the moment, the real show stopper seems to be how to read the curves optically with the same precision that we can to mechanically. The subsequent steps are, essentially, not that advanced math. I just would like to have it ready when the imaging problem is solved ...
(No, I am not expecting to be able to build such an optical pick up; I just use the problem as a mental toy.)
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Fascinating solution!
However, the guy in the video seems very focused on 'no digitalization', direct to analog. That means you have no option to use digital techniques to e.g. handle scratches, dust particles etc.
The video doesn't tell anything about how the laser beam is read. The simple 2D figure shows two laser beams perpendicular to the sides, but how do you then detect how far away the side is? How is the amplitude measured? I wouldn't be surprised if that is a business secret ...
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If he is really determined to stay analog, I'm betting you could get an analog signal from the laser reflections. Just raise the price even more -- all of those analog-loving audiophiles will still beat a path to your door!
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Mono recording uses 90/180 degree wiggles. In other words, left to right wiggles. Stereo uses 45/225 degree wiggles for one channel and 315/135 degree wiggles for the other channel. So if a mono record is played on a stereo cartridge, the same signal appears in both channels. If a stereo recording has a perfectly centered sound, it would be (almost) 90/180 degree wiggles. This is one of the reasons why exact cartridge alignment makes such a difference in sound quality.
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#Worldle #278 2/6 (100%)
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https://worldle.teuteuf.fr
"A little time, a little trouble, your better day"
Badfinger
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I'm using a Dockteck 7-in-1 USB C Hub Multiport Adapter connected to a Dell XPS 17 9710 laptop.
The ethernet cable from the Dockteck, and the ethernet cable from another laptop, connect to my 24 port router and then the cable modem.
Now here's the fun part. During "heavy" upload, copying files to a server or sharing my screen in Teams, Dell XPS loses internet occasionally. The only thing that restores the hardwired connection is a full reboot.
Now here's the weird part. The other laptop also loses its hardwired connection! Rebooting the first laptop restored the other laptop's internet connection.
WTF? Why is there a dependency? I suppose I could try plugging in both cables directly to the modem box as it has enough ports, or maybe the modem box is barfing for who knows what reason and that affects everything?
Gremlins, I say.
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connect both laptops to modem. mine has 2 available ethernet ports on modem. I have seen such weirdness when I used multi-port adapter. I use 2 desktops.
"A little time, a little trouble, your better day"
Badfinger
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jmaida wrote: connect both laptops to modem
Done!
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I almost always blame the elephanting all in one wireless router/modem boxes ISPs saddle you with. They are dodgy as heck in my experience.
To err is human. Fortune favors the monsters.
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I agree. I have gone through several in last 3 years. Last one is Xfinity's top of the line. Better but dodgy at times. I bought one (cisco modem) with separate wireless interface and it worked good until Comcast decided they were no longer compatible. Grrr.
"A little time, a little trouble, your better day"
Badfinger
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1. See if the USB/Ethernet device is getting real hot.
2. I have 2 USB3 to Ethernet "dongles", both have 3 USB3 ports. One works on Windows/Mac/Linux/Pi. The other "sort of" works on Windows and Linux. It also gets very hot.
I have never had a disconnect due to the cable companies router, I have had them die and Comcast decides to unplug stuff from time to time, but they always admit it and reassure me that their techs are "working very very hard" to fix it. I tell them they should work smart, not hard
>64
Some days the dragon wins. Suck it up.
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theoldfool wrote: See if the USB/Ethernet device is getting real hot.
Yes it does, and I also have a monitor running off the HDMI connector, so it's a busy little beast.
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Possibly the 24-port hub/switch has a problem. I’ve seen only one in 25 years have a problem, but it happens. But as another person said, plug the Dockteck into the modem and see if that solves it. At least you’ll know.
Good luck.
Time is the differentiation of eternity devised by man to measure the passage of human events.
- Manly P. Hall
Mark
Just another cog in the wheel
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Mark Stars post inspired these additional thoughts.
Try a different port on the switch, Try a different cable (if you are plugged into modem and still have problems)
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