CDs: More to Talk About (Sony vs. Philips)
Where's the comparison, between the philips and sony tracking, mechanisms, or did I miss that did, I miss it or did you forget to explain the Sony solution, for keeping the laser on track and in focus, how does sony do the tracking the, rest of that comment was really insightful thanks for sharing okay, could I have been a little more clear I'll show you a Sony system later on but if you didn't see my last thing yes, yes, I could have but, this is in fact later on so, perhaps maybe we shouldn't jump to conclusions so quickly tell. You what I'll work on being a little more precise in my choice of words and perhaps you, dear viewer could, refrain from jumping to conclusions, quite, so quickly if we put our minds to it together we can enhance our understandings, through complex, thought both on the part of the speaker and on. The part of the listener and. Alright. This video is coming at you in three parts as we discussed in the last video no wait wait wait, the, ding was way too loud let's tone it down much. Better so. As we discussed in the last video we're, going to take a look at some of the waveforms, coming from the components, of this Magnavox, which is really a rebadged, Phillips, because Phillips couldn't use that name in the US due to its passing similarity to Philco I guess but that's a stretch CD, player that, will be part 1 in, part 2 we'll take a look at a Sony laser pickup and discuss the differences plus, I will tear this one apart to expose the laser diode and photo diodes and in, part 3 we'll discuss why Sony's pickup solution would become the default standard used, to this day and optical drives we'll begin with part 1 and part, 1 will be quite a bit different from most other videos that's, because much of it is unscripted. Off-the-cuff. Just, gonna wing it yeah. But first a few Corrections, as usual, the Internet has provided answers, that I did not find and has revealed some mistakes and false assumptions, from the last video of course. But, that's ok we all make mistakes and, now I'm gonna tell you what we learned thanks to the diligent research of more knowledgeable, people than me remember. It's ok to not know everything and it's, ok to ask for advice from professionals, and that's, let me reveal the most dumb mistake, and it was right on screen the, best, kind of mistake, I had. Been assuming that pin 10 was the output signal from the focus chip and that it, would be a binary stream, from the pits and land boy, was that wrong on many counts first, it's not pin ten that does that it's pin three then it's labeled right here on the datasheet pin. Three is also labeled to decoder which I missed and most. Importantly, it's a sum of the outputs from hall for photo diodes as illustrated, right, here yes, pin 10 also gets the sum of the four diodes but unlike pin 10 pin 3 has an amplifier, equalizer and another amplifier to boost the output. Mm-hmm. I want to give a big thanks and shout out to Zim 0 2 5 6 who not only created the helpful, diagram, that I used on a few occasions but, who also gave more complete info on what is going on the.
Motorola Processor, is a custom, chip based around an H c08, microcontroller. And it is in fact the decoder, that is doing most of the work I couldn't, find its datasheet because the P on the end was limiting my search results, and, to think we just learned about minding, our P's and Q's anyway, in fact the decoder is handling all the raw data undoing, the 8 to 14 modulation, isolating, the sub code and all that it even, digitizes, the output from pin 3 which at this point is still analog, which we'll see in a moment it, sends the extracted, sub code to the processor. So it knows how to handle the disk and respond to user requests, really. The processor, is just managing the living and breathing tasks, of the machine such, as the user interface, display, and other goodies like popping, the disc tray in and out and getting the whole process going speaking of the disc tray a few people had asked how the machine can tell that the disc tray has been pushed in manually, as opposed, to someone hitting the open closed button some. Other people noticed this strange button, switch near the decoder these. Two groups of people are discussing the same thing to. The right of the disk tray is a little series of levers that rest on top of this button when it's assembled little. Nubs on the bottom of the tray will cause this to push down on the button in either the open or closed position this. Not only tells the processor, that the tray has reached the end of its travel in either direction but it also means that it can detect if the tray has been pushed in as, the button will be released and lest the switch open as soon as the tray is moved out of its open position okay, it's time for this script to be put to the side I've got a sort of odd setup here because I need to see both the oscilloscope screen and what I'm poking on the board so we're going to do some picture and picture editing, magic and throw the scope screen up hi, excellent. And you know what maybe we'll throw another camera, up here somewhere so that you can see what I'm doing even, better all of the cameras, all the tripods, while, this is awkward. They. Don't have to do as. Promised, we're gonna poke around on some of the things here now I brought my laptop here so I can actually go and look and see what I'm looking at and you'll, notice these uh wires. That, I've soldered on to chips underneath I'll bring. Up the image of that part, of the issue with this player is that it has to be the. Ribbon, cable between the drive, and the board is very very short and there's, pretty much no way to operate, this unless. It's assembled I really, don't know how people would service these things because it you know a lot, of the a lot, of the stuff. That I want to see is underneath, the CD reader like the the. Tracking and focus chips are basically directly under here that's. Not helpful, but, we could see what else we can take. A look at I did. Find, just, from poking, at one point I found me. The. Raw data stream, I think, it was one of these guys, unfortunately. What, is happening, here Oh. Well, this is kind of interesting what's, I wonder what's on this line let's see if I can figure it out notice. That we're. We're. On a really long time scale I think. This is the sub code if, I can hopefully, get, the triggered. I'm. I'm. Really, I have no experience with a scope so just just, so you know. Let's. Try. Oops. That's what I meant that's what I meant the other way oh it's. Probably you okay. Yep. Okay I found. It so, this, here, is the waveform that's, coming from the.
Amplifier. Chip from me art from the. TDA 808. II I want, that one so, this this, is the amplified. Output of. The. Oops. Of the, pits and land so this is the raw analog, signal, coming from the disk, and if. We look a little closer you. Can. See if I touch the disc, see. How that's, well. I've killed it, great. Great. Job so, if I kind of just touch it you can see the it. Slows down a bit now. You zoom out a bit OOP zoom, out a bit. See. That. Just. Completely it, gave up their that, click sound you heard I believe, is the laser, kicking. Up all the way. But. Yeah so this this, isn't the raw output from the photodiodes but this is the amplified, output coming from pin three going. To the, decoder the, output from the photodiodes is. Very. Very small, this is, and. Take a look compared in the voltage level there's almost nothing there and. It's so noisy I can't see anything these. All should be. The. Same. There's. Nothing, there. Which. Is a shame because I really wanted to show you that oh. Well. I. Wanted. To show you some interesting stuff and I think that we saw some interesting things but. Not. As many as I was hoping well. With that disappointing, segment out of the way let's move on to the part that I didn't forget about to. See how Sony handled, the optical system differently we, need to get our hands on a Sony CD player hopefully, of similar vintage to this Philips one opor. Fect a Sony CD changer, from 1992. Now. It doesn't really matter that it's a changer there's still a standard, CD mechanism, in here it's just on the pivot and will happily pop up and fall down to greet or say farewell to the disc hit plays it. Works in tandem with the disc tray which rather than just being in any Audi operation. It's an inny Audi with rotational, flair now, I embarked, on the frightening task of getting this mechanism out of this player armed. Only with an ordinary screwdriver, I went ham-fisted and, started unscrewing, stuff, before. I realized I hadn't, filmed the close-up segments, of the laser tracking, a disc, after. Undoing, what I had begun I began once more the, screws are the enemy be gone or, be, twisted counterclockwise sufficiently, until such time that they can be gone having. Gained unrestricted, access to our prize I loosened, at the forest bruise holding it in place but, it wouldn't budge, yet, more screws needed liberation, until finally, I had successfully, removed the crown jewel from the temple of forbidden. Technology, and here. It is one, of the big differences you'll see between this and the Phil mechanism, is everything. Is much more integrated, in fact. This one chip here if the datasheet I found is it all correct link below has, 32, K of RAM built-in does, the e FM demodulation as, well as the circ error correction, handles, the focus tracking and spindle motor using, this chip as a driver to handle the power extracts. The sub code provides, a data output for the DAC and can even do such exotic things as double speed playback and variable, pitch playback, assuming, the player it's inside has those functions enabled did, I mention its bilingual, it's interesting how just four, years time managed, to integrate functions, that are spread out via multiple, chips on this Philips machine into, just this one chip on the board of the laser pickup but, that makes a lot of sense see this Philips board only works with one mechanism because. It's driver components, are part of the mainboard design anything. But if philips cdm-t. Some. Modification. But, for the sony machine this, ribbon cable is essentially, just providing a power ground, a communication, bus to the cpu and a data stream for the DAC this. Component, can be completely. Redesigned, and so long as it accepts, the same inputs and produces the same outputs the mainboard really, won't care this. Allows Sony to make production improvements, and even radical changes, to this mechanism and how it works without disturbing, the mainboard you can see how Sony played a modular, approach via the markings on the board this, one board was used in many different players with different components marked, Forex player only by. My count it was used in at least five players really. Sony's, markings, are just a lot more helpful wondering. Which one of these is the DAC Hey look it's labeled right here and you'll, find a pulse chip on the bottom I'm, pretty sure these are one bit Dax based on some vague research I'm sure someone will correct me if I'm wrong and I'm counting on it and the, fact that they've labeled these jumper, connections, on the top of the board for what, they are sure is helpful that.
Would Have been nice, Philips anyway. Back to the laser because that's the real difference first. Gone is the swingarm instead. The laser is mounted on a sled which moves linearly, with, the help of this rack and pinion drive now. You might suspect that this drive arrangement, does not have the precision to track the disc the, floating arm of the Philip system means it can move subtly, and precisely to track an off-center. But this brutal, in elegant plastic gear train can't possibly, be used for the tracking and. It isn't just, like the Philips system this lens is floating, and can move up and down but, unlike, the Philips system this, lens can also move left and right with. The help of a diode I have lying around you can see that the laser can move quite a bit to either side, let's. Take off this plastic shroud to get a better look this, one is perfect. For showing this yes, okay. I'm sure, you can see these rectangular, coils, surrounding, a vertical structure these. Coils will push the lens upward if a voltage is passed through them but. If you look very carefully you'll also see a pair of circular. Coils on the outer edges when, a voltage is applied to these depending, on the polarity it will attract itself to these handy, magnets, placed on the sides or it will push itself away, this, causes the lens to pivot either left or right depending on which way you slice it the best part of this setup is that the lens is completely. Independent, of the sled that it's riding on if the sled moves a bit it doesn't care they will just react to that movement as though the track of pits it's tracking. Has moved slightly that. Means that the sled only has to move in course steps and the lens will take care of the rest but that's just one significant, difference the, other is in the photodiode arrangement, you, may have seen the term three-beam. Laser tracking. Before. Or something like that in these, systems rather than using only for photo diodes, like in the philips system we use six in, the middle our four cells arranged. Actually. Exactly like the philips system these are used in an identical fashion for, focus an elliptical, reflection indicates an out-of-focus beam and as orientation indicates. If focus is near or far but. To correct tracking, errors two additional, diodes to either side are monitoring, for an off-center being in these systems a diffraction grating splits, the laser beam into three in reality. It splits into two infinite beams of increasingly, weak intensity as they deviate from the center but we only care about the center beam and the two immediately surrounding, it now. When, tracked correctly the outside, beams shouldn't, land on the stream of pits they, should instead land just outside of them which, will that's caused them to reflect the featureless, boundaries, the, reason this works to track the stream is that if the track deviates, suddenly. One of the tracking diodes, will start seeing the data stream that's. Not supposed to happen, so the player will react by nudging the lens in the direction of the activated, tracking diode this system is certainly more complex, on the hardware side but, given how simple the trigger is no, need to compare ratios simply see if a single, thing is happening it's, probably, a lot easier to implement however. This, makes me wonder if the system is fundamentally worse, at tracking, disks see. I've heard anecdotal, evidence that the original Philips single beam tracking, is superior, at tracking scratched or damaged, disks and with. The knowledge of how the three beam tracking works that. Kind of makes sense, imagine, a scratch appears, just next, to the data stream if that, scratch is bad enough it might Bend one of the tracking beams toward the raw data stream causing, the lens to deflect for a defect that isn't really there what's, the Philips system it wouldn't see this scratch because it only has the one scanning, beam it, would ignore it and thus be unaffected now. Of course these conventional, systems aren't remarkably, inferior, they can tolerate scratches, pretty well too but. It makes me wonder if there is truth to the anecdote, that the swingarm servo, Phillips single beam tracking whatever is, indeed superior one, last thing before we answer why this became the standard I'm, not afraid to tear this apart and find what's inside so first, you can see the actual laser diode here as opposed to the Philips machine where it's housed in this plastic this, like in the Philips setup projects, the light sideways, where it hits a prism gets, shot up at the disk surface which the floating lens helps to keep tracked and focused and it gets reflected back goes straight through the prism and lands, on this little chip here now.
This Is interesting because on this machine we can actually see the backside of the photodiode, array unlike. On the Philips machine where we could only see the board if I keep going to remove the lens and get everything apart you can see the prism in here take, a look it does a great job of reflecting light at a 90 degree angle and now, let's see what we can see of the photo diodes well. Don't get your hopes up they are pretty much microscopic. To, be fair we are dealing with laser light focused, on microscopic. Pits so it stands to reason that these are probably, pretty small I don't have a microscope, handy yet. But. I do have my ridiculous. Macro lens set up so I could get these extreme, close-ups, you, can definitely see, that these are three clusters with one used for data capture and focus, control, and the to to either side for tracking to. Show how small this is I've placed a dime next to it for scale for. A more international perspective, how about a microSD, card and just, for fun here's the point of a safety pin these, really, are tiny, so, now why did Sony's floating lens and stepping platform, become the de-facto method, of reading optical, discs with. More photo diodes and greater mechanical, complexity, you, might think it to be inefficient well. It may be inefficient, in some ways but, in most ways it's in fact much more efficient. First. Let's take size if, we look at the Filip system you'll notice that the entire laser, pickup is essentially, behind, the disk the. Pivot point for the swingarm has to be farther to the rear of the player otherwise. It would simply rotate around the circumference, of the disk and that, would it be very helpful this off the bat limited, its potential to miniaturize, and boy, did this get smaller quickly, portable. CD players burst on the scene in 1984. And they would only continue, to get smaller with, one CD, player featured by tech Mon actually, being smaller than a CD, and that was in 1988, the same year as this Philips machine was made in fact, this very mechanism is larger than it needs to be if these, parts were shifted downward, it could be no longer than the distance here and this. Laser platform, could get smaller and smaller and smaller until, eventually you're, into modern, slim drives for pcs which have the tiniest, of lenses and thinnest, of assemblies, and the PC, market would only continue, to make this Philips system harder to justify in fact, one fatal flaw of the Philips reader would make sure it fizzled into obscurity its, mass, imagine. In a portable player which can be set in any position or even moved around while playing that, it had this swinging, laser pickup it's, so loosey-goosey. That it's doubtful that will track very well and its. Mass also limits how quickly it can move when. Cd-rom, drives appeared, and getting, faster, and faster and faster the. Laser would have to be able to wiggle itself back and forth at frequencies, in excess of 10 kilohertz. That's. Easy if you're just wiggling a small piece of plastic back and forth but, a lot harder if you're wiggling this big swinging, thing and so, Sony's three-beam, laser tracking, would be miniaturized and improved over the years developments. An anti skip functionality, meant that CD, walkman, could be tossed around without fear of skipping, or glitches or getting, stuck repeating a bit of the track that. Was accomplished, simply by reading the disk at faster, than normal speeds creating, an intermediary, data, buffer, between the disk and the processor, the, DAC could have upwards of 40 seconds at its disposal for the laser to get back on track and resumed the data stream which, thanks, to the timecode is easy to piece together if a problem does arise thus, eliminating, the effects of skipping and of course later on the wavelength of light would change to read packing, the pits closer together and creating the Meuse high-definition, laser disk and then, later the DVD, and obscured digital format you might have heard of later. We'd say enough, with the read in with the blue and, we'd be packing upwards of twenty five gigabytes, unto a slightly different silver, plastic thing after.
We Briefly, re-enacted, the videotape format Wars of the 1980s, because, why not but, we're getting ahead of ourselves there's, lots, more to talk about when. We next check in on optical disk technology will. Discuss the yellow book the standard published in 1988, that defines the specifications. Of the cd-rom, then. We'll talk about some writable, dis technologies, like CDR, and cd-rw and. Then, if interest persists, we might dig a little deeper into the DVD and some of the follies of its development such, as how this logo mysteriously. Features a disk for, a solid-state. Memory format. Hmm. Thanks, for watching I hope you enjoyed the video if you missed the first two videos on the compact disk you can check them out in the playlists on digital sound that will quietly, pop up above me so. Serene, as always. A great big thank you to everyone who supports this channel on patreon, especially. The fine folks that are scrolling up your screen if you're, interested in pledging some support to the channel to help it grow please, check out my patreon page thanks, for your consideration and, I'll see you next time. Hey. One thing my most viral, video to date was about how Sony used the tracking servos, and a CD player to create the copy protection scheme, in the original PlayStation, you, might want to check that video out but be, warned that there are a number of annoying, things, about the flow of information over, there it. Goes into a lot of detail, about the PlayStation, and some of its history and the comments, on there if you dare to look at them indicate, that many people were, not. Happy about it so if you haven't seen it check it out and apologies. In advance and. Another, thing, so, if you didn't know there's a second, channel technology connections. To where, I upload weird. Stuff from time to time and I, just uploaded, a video of a couple of CD players that, are very similar but have some unique differences, so if you want to check it out please, feel free to click the link down below or, up above.