WEBVTT - Audio Wars: Analog vs Digital 0:00:04.400 --> 0:00:07.800 Welcome to tech Stuff, a production from I Heart Radio. 0:00:12.160 --> 0:00:15.200 Hey there, and welcome to tech Stuff. I'm your host, 0:00:15.360 --> 0:00:18.240 Jonathan Strickland. I'm an executive producer with I Heart Radio 0:00:18.320 --> 0:00:21.640 and I love all things tech and recently I received 0:00:21.720 --> 0:00:26.200 a tweet from Twitter user Salvatore del Knock, a k 0:00:26.400 --> 0:00:30.320 A non juror, asking if I would do a breakdown 0:00:30.720 --> 0:00:33.840 on how analog to digital and digital to analog audio 0:00:33.920 --> 0:00:38.040 converters work. And that's a great request. Um, it is 0:00:38.200 --> 0:00:41.440 incredibly technical when you really get down to it. So 0:00:41.560 --> 0:00:45.360 I'm going to do a very high level view of 0:00:45.400 --> 0:00:49.360 the concept because otherwise we're gonna have to get into 0:00:49.960 --> 0:00:54.560 the various methodologies that DAC and a d c's work, 0:00:55.120 --> 0:00:58.560 and uh, it would quickly become like a technical manual. 0:00:58.680 --> 0:01:01.600 But if people want that, then I can do a 0:01:01.680 --> 0:01:04.880 subsequent episode and go into more detail. But one of 0:01:04.880 --> 0:01:08.119 the things about this is that lets us talk about 0:01:08.160 --> 0:01:13.160 the differences between analog and digital audio and why converters 0:01:13.200 --> 0:01:15.720 are necessary in the first place, and to open up 0:01:15.760 --> 0:01:19.640 the eternal argument about whether one is inherently better than 0:01:19.800 --> 0:01:22.640 the other. This one goes out to all you audio 0:01:22.720 --> 0:01:26.120 files out there, so get ready to send me angry messages, 0:01:26.120 --> 0:01:28.679 because no matter what I say, some of y'all are 0:01:28.720 --> 0:01:32.040 going to get upset. Anyway, let's start with what it 0:01:32.080 --> 0:01:35.920 means to be analog versus digital. Now, when I was 0:01:35.959 --> 0:01:38.640 a young boy, nobody loved me. I was a poor 0:01:38.680 --> 0:01:43.280 boy from a poor family. No, hang on, that's now, 0:01:43.280 --> 0:01:46.440 that's Queen's bohemian rhapsty Now, when I was a young boy, 0:01:46.560 --> 0:01:51.200 analog was the standard. Digital did not even enter into 0:01:51.200 --> 0:01:54.720 my awareness until I was a teenager, when compact discs 0:01:54.720 --> 0:01:56.640 were starting to become popular. They had been around for 0:01:56.640 --> 0:01:59.160 a while before I was a teenager, but I was 0:01:59.240 --> 0:02:02.680 not really aware of them, because I mean, I grew 0:02:02.720 --> 0:02:05.120 up in rural Georgia. We would get technology a few 0:02:05.200 --> 0:02:09.560 years behind everybody else. Anyway, I grew up thinking analog 0:02:09.680 --> 0:02:13.680 essentially meant old and digital meant new, Like that was 0:02:13.760 --> 0:02:16.280 the sort of the abstract distinction between the two in 0:02:16.360 --> 0:02:20.000 my head. But the differences are obviously more complicated than that, 0:02:20.400 --> 0:02:23.560 and we need to understand how sound works, which I 0:02:23.600 --> 0:02:26.720 know I've covered many many times, but it's important so 0:02:26.800 --> 0:02:29.760 that we know how the analog and digital methods of 0:02:29.840 --> 0:02:35.120 recording and thus reproducing and eventually playing back sound. You 0:02:35.160 --> 0:02:38.760 know how they work with relation to the original sound 0:02:39.000 --> 0:02:43.280 that existed. So sound is, when you really get down 0:02:43.320 --> 0:02:48.720 to it, vibration or pressure waves. Now, we mostly experienced 0:02:48.720 --> 0:02:52.320 sound by hearing these vibrations travel through the air, but 0:02:52.520 --> 0:02:55.840 you can also experience this underwater. Sound can move through 0:02:55.880 --> 0:02:59.600 different media, including solid material. Like if you put your 0:03:00.040 --> 0:03:02.639 ear against a table, a really long table, and some 0:03:02.720 --> 0:03:06.280 one on the other end is tapping very lightly on 0:03:06.360 --> 0:03:09.560 that table, you'll hear it. And it's not because the 0:03:09.560 --> 0:03:12.400 sound is traveling effectively through the air, though it is 0:03:12.760 --> 0:03:15.480 doing a little bit of that too, but that it 0:03:15.560 --> 0:03:19.320 travels through the table to you. Sound also travels at 0:03:19.360 --> 0:03:23.000 different speeds through different media, and in fact, stuff like 0:03:23.080 --> 0:03:26.520 air temperature can affect how quickly sound travels, which is 0:03:26.560 --> 0:03:30.240 why when we talk about the speed of sound, we 0:03:30.400 --> 0:03:33.440 technically actually need to be a little more specific than that. 0:03:33.800 --> 0:03:36.480 So the standard way of describing the speed of sound 0:03:36.680 --> 0:03:39.960 is to say that it moves at three per second 0:03:40.160 --> 0:03:44.840 in dry air at twenty celsius, that's about sixty eight fahrenheit. 0:03:45.240 --> 0:03:47.960 And if you start changing those parameters, you know, if 0:03:47.960 --> 0:03:50.480 you introduce, say a lot of humidity into the air, 0:03:50.960 --> 0:03:53.840 or you change the air temperature like it goes up 0:03:53.960 --> 0:03:56.520 or it goes down. Well, sound will travel at a 0:03:56.600 --> 0:04:00.840 slightly different speed than at that standard I was talking about. 0:04:01.160 --> 0:04:04.160 Now I could get into how the vibrations cause air 0:04:04.160 --> 0:04:06.880 molecules to move back and forth, creating little changes in 0:04:06.960 --> 0:04:11.480 air pressure. And it's these pressure waves, these air fluctuation changes, 0:04:11.520 --> 0:04:13.520 that our ear drums pick up and transfer to our 0:04:13.560 --> 0:04:17.200 inner ears. That's where special nerves pick up these fluctuations 0:04:17.200 --> 0:04:19.760 in our inner ears, and then our brains process those 0:04:20.200 --> 0:04:23.120 those nerve signals as sound. But most of this isn't 0:04:23.160 --> 0:04:27.280 important for the rest of this episode, so instead, let's 0:04:27.320 --> 0:04:31.960 talk about sound waves, all right. So we can think 0:04:31.960 --> 0:04:34.599 of a vibration as something in which a particle is 0:04:34.640 --> 0:04:37.960 moved out of its usual place and then it snaps 0:04:38.040 --> 0:04:40.640 back to its usual place, and it might do this 0:04:40.880 --> 0:04:44.279 several times. Think of a guitar string. If you pluck 0:04:44.320 --> 0:04:47.280 a guitar string, you're pulling the string out of where 0:04:47.320 --> 0:04:50.719 it usually sits, and then it snaps back and forth 0:04:51.000 --> 0:04:55.880 and oscillates around its normal position until it settles down again. 0:04:56.240 --> 0:04:58.919 So we can describe the number of times that a 0:04:59.000 --> 0:05:02.440 particle does as a frequency, you know, or the number 0:05:02.440 --> 0:05:05.800 of times a string goes from one point all the 0:05:05.839 --> 0:05:08.960 way across and back to that starting point over the 0:05:08.960 --> 0:05:11.520 course of a second. So with sound, we usually use 0:05:11.560 --> 0:05:16.080 the unit hurts to measure frequency. If a particle only 0:05:16.120 --> 0:05:19.680 did one cycle of vibration per second, if it took 0:05:19.680 --> 0:05:22.560 a full second for it to go from the you know, 0:05:23.120 --> 0:05:29.240 the one crest to the next crest, uh, then it 0:05:29.279 --> 0:05:31.640 would be one hurts. That would also, by the way, 0:05:31.680 --> 0:05:33.560 be a frequency that was way too low for us 0:05:33.600 --> 0:05:36.760 to hear. Typical human hearing has a range of around 0:05:36.839 --> 0:05:40.480 twenty hurts at the low end, to twenty thousand hurts 0:05:40.560 --> 0:05:43.160 or twenty killer hurts, in other words, on the high end. 0:05:43.640 --> 0:05:46.880 So for stuff vibrating in a cycle that's twenty times 0:05:46.880 --> 0:05:50.119 a second all the way up to twenty thousand times 0:05:50.120 --> 0:05:53.320 a second, that's something we could potentially hear. Now. I 0:05:53.360 --> 0:05:57.280 say potentially because that is typical human hearing. There are 0:05:57.279 --> 0:05:59.640 people who can hear outside of that range a little bit, 0:06:00.120 --> 0:06:02.760 and then there are some of us, especially as we 0:06:02.800 --> 0:06:07.080 get older, who can hear a more narrow range of frequencies. 0:06:08.120 --> 0:06:11.080 But frequency is just one part of how we describe sound. 0:06:11.440 --> 0:06:14.600 We can also describe sound by how loud it is. 0:06:15.160 --> 0:06:18.640 The volume of sound. So from a physics perspective, we 0:06:18.680 --> 0:06:21.159 can think of this is how much pressure the sound 0:06:21.200 --> 0:06:24.200 places upon our ear drums. You know how dramatic those 0:06:24.200 --> 0:06:28.240 fluctuations and air pressure are. In other words, But loudness 0:06:28.400 --> 0:06:31.680 isn't just down to physics. The way we experience loudness 0:06:31.680 --> 0:06:35.880 depends not just on that sound pressure itself, but stuff 0:06:35.920 --> 0:06:39.479 like psychoacoustics. That's how our brains perceive sound in the 0:06:39.520 --> 0:06:43.360 first place. But now we've got two criteria we can 0:06:43.480 --> 0:06:46.200 use to assign to any sound correct Like, we can 0:06:46.279 --> 0:06:49.440 talk about the frequency of that sound, you know, how 0:06:49.480 --> 0:06:53.120 frequently that those particles are vibrating, And then we can 0:06:53.160 --> 0:06:56.200 also talk about the displacement of those particles vibrating, or 0:06:56.240 --> 0:06:58.839 what we might think of as the loudness or volume 0:06:58.920 --> 0:07:02.520 of that sound. We could then plot a sound wave 0:07:02.800 --> 0:07:06.200 as a transverse wave on a graph, and we could 0:07:06.200 --> 0:07:09.400 have the X axis, you know, the horizontal axis of 0:07:09.440 --> 0:07:13.080 this graph representing the passage of time. So on the 0:07:13.160 --> 0:07:15.800 left side we might say zero, and we say time 0:07:15.840 --> 0:07:18.679 increases as you go to the right. The y axis 0:07:18.760 --> 0:07:22.400 we could have being displacement, which kind of you know, 0:07:22.440 --> 0:07:25.960 amplitude or volume in other words, and we could then 0:07:26.000 --> 0:07:29.360 plot all the points where a particular vibrating particle would 0:07:29.360 --> 0:07:33.400 occupy over a given span of time. If we had 0:07:33.560 --> 0:07:36.880 a sound of a steady frequency, then we would end 0:07:36.920 --> 0:07:38.440 up with a wave that would look a lot like 0:07:38.480 --> 0:07:42.240 a sign or cosign wave. The distance between two consecutive 0:07:42.320 --> 0:07:47.000 crests of this wave would be the wavelength for that sound, 0:07:47.280 --> 0:07:52.080 and the sounds wavelength has an inversely proportional relationship with 0:07:52.160 --> 0:07:56.120 the sounds frequency, So the higher the frequency of sound, 0:07:56.760 --> 0:08:00.160 the shorter the wavelength will be. So deep bay Ace 0:08:00.280 --> 0:08:03.920 notes would have sound waves that have much longer wavelengths 0:08:04.240 --> 0:08:09.120 than very high pitched high frequency notes. Uh frequency relates 0:08:09.160 --> 0:08:12.840 to pitch. There isn't like an easy mathematical way we 0:08:12.920 --> 0:08:17.000 can kind of relate pitch, by the way, There are 0:08:17.120 --> 0:08:20.160 easy ways we can relate frequencies, but it gets a 0:08:20.160 --> 0:08:25.640 little tricky anyway. The reason I even talk about plotting 0:08:25.720 --> 0:08:28.560 sound waves at all is that it makes us easier 0:08:28.600 --> 0:08:31.720 for us to consider the differences between analog and digital 0:08:31.760 --> 0:08:34.760 audio recording. Keep in mind, if we plotted that sound wave, 0:08:35.200 --> 0:08:38.640 that's not that's not the physical sound wave that we've 0:08:38.679 --> 0:08:43.160 just plotted. That's our description of that sound wave, its frequency, 0:08:43.200 --> 0:08:47.439 and its loudness. Um The classic sign wave like depiction 0:08:47.480 --> 0:08:49.840 of the sound wave shows us that there's a continuous 0:08:49.960 --> 0:08:55.199 representation of sound across time. It is unbroken. We can 0:08:55.480 --> 0:08:58.360 put plot, you know, even complicated sounds with changes in 0:08:58.400 --> 0:09:01.640 amplitude and frequency, and the shape of the waves tells 0:09:01.720 --> 0:09:05.320 us a little bit about the tambre or quality of sound. Now, 0:09:05.320 --> 0:09:08.440 by quality, I don't mean, oh, this sound is very 0:09:08.480 --> 0:09:12.440 good quality or this sound is really bad quality. Instead, 0:09:12.480 --> 0:09:17.960 I'm talking about the elements that differentiate say piano playing 0:09:18.160 --> 0:09:22.480 middle C from a guitar playing that same note middle C. 0:09:23.040 --> 0:09:26.880 Both instruments are producing the same note at the same frequency, 0:09:27.000 --> 0:09:29.719 assuming both instruments are you know, properly tuned, and both 0:09:29.800 --> 0:09:33.000 of them are using the same pitch tuning, but you 0:09:33.040 --> 0:09:36.560 would hear a difference in the type of sound between them, right, 0:09:36.640 --> 0:09:41.199 A piano and a guitar sound different. Otherwise all instruments 0:09:41.200 --> 0:09:44.560 would produce exactly the same kind of sound as each other. 0:09:45.080 --> 0:09:46.959 But you know, you can tell the difference between a 0:09:47.000 --> 0:09:50.439 piano and a guitar, or a clarinet or a flute 0:09:50.520 --> 0:09:54.480 or whatever. The tambre is different, even if the instruments 0:09:54.480 --> 0:09:58.000 are all producing you know, technically the same frequency, even 0:09:58.040 --> 0:10:01.040 at the same volume. This leads us to the fact 0:10:01.120 --> 0:10:05.040 that sound is this continuous thing for us. It isn't 0:10:05.080 --> 0:10:08.720 happening in discrete units. It's kind of like the difference 0:10:08.760 --> 0:10:12.480 between jumping into a pool filled filled with water, which 0:10:12.559 --> 0:10:15.320 is you know, continuous to us because we can't you know, 0:10:15.600 --> 0:10:19.480 experience it down on the molecular level, or jumping into 0:10:19.480 --> 0:10:23.199 a pool that's filled with plastic balls. So to us, 0:10:23.600 --> 0:10:27.440 sound is kind of like a fluid, and analog recording 0:10:27.600 --> 0:10:33.200 captures that. The analog approach to recording is older than digital. 0:10:33.400 --> 0:10:37.320 So way way back in the nineteenth century, folks like 0:10:37.360 --> 0:10:39.480 Alexander Graham Bell, we're trying to figure out how to 0:10:39.520 --> 0:10:43.600 transmit the human voice across great distances using electricity, and 0:10:43.720 --> 0:10:46.679 the microphone was one half of what was needed to 0:10:46.720 --> 0:10:50.000 do this, the loud speaker being the other half. And 0:10:50.200 --> 0:10:54.240 the basic way a standard microphone works is to convert 0:10:54.559 --> 0:10:59.160 sound that continuous you know phenomena of pressure wave changes 0:11:00.080 --> 0:11:03.600 to a varying electric signal, an electric signal that has 0:11:04.280 --> 0:11:08.880 varying voltage. This is another continuous phenomena, right, it's unbroken, 0:11:09.000 --> 0:11:12.440 it's it's like another wave. Here's how it works. So 0:11:12.520 --> 0:11:17.559 inside an analog microphone is a tiny little diaphragm, typically 0:11:17.640 --> 0:11:20.000 made of very thin plastic, and it behaves in a 0:11:20.040 --> 0:11:23.960 way similar to how our ear drums work in our ears. 0:11:23.960 --> 0:11:29.480 So when sound, you know, these pressure waves hit that microphone, 0:11:29.840 --> 0:11:33.240 it moves the diaphragm back and forth, and the diaphragm 0:11:33.280 --> 0:11:37.320 is actually attached to an electro magnet. A simple microphone 0:11:37.400 --> 0:11:40.679 could have a permanent magnet inside it, and wrapped around 0:11:40.679 --> 0:11:43.680 this permanent magnet is a little coil of metal wire 0:11:43.920 --> 0:11:47.160 that connects to the diaphragm. So the diaphragm moves the coil, 0:11:47.320 --> 0:11:50.560 which then moves along the length of this permanent magnet. 0:11:51.280 --> 0:11:54.640 That introduces a fluctuating magnetic field, or rather, you know 0:11:54.720 --> 0:11:58.240 the effect of a fluctuating magnetic field. The permanent magnets 0:11:58.280 --> 0:12:01.920 magnetic field is stable, but moving a coil through a 0:12:01.960 --> 0:12:04.520 magnetic field, it's the same thing as if you were 0:12:04.559 --> 0:12:08.680 to fluctuate a magnetic field around a you know, non 0:12:08.720 --> 0:12:12.640 moving coil, you get the same effect. Now, the laws 0:12:12.640 --> 0:12:16.160 of electromagnetism tell us that if you have a conductive 0:12:16.200 --> 0:12:21.200 material and it encounters a fluctuating magnetic field, that field 0:12:21.640 --> 0:12:25.840 will then induce an electric current in the conductive material. 0:12:25.960 --> 0:12:29.920 So now you've got the microphone producing an electric current, 0:12:30.400 --> 0:12:33.640 and again the voltage of this current varies depending upon 0:12:33.720 --> 0:12:37.679 the sound hitting the microphone. That means the microphone is 0:12:37.720 --> 0:12:41.040 a type of transducer. That's a device that converts one 0:12:41.120 --> 0:12:44.880 form of energy, in this case acoustic pressure, into another 0:12:44.920 --> 0:12:49.040 form electric signals. Now, you could send this electric current 0:12:49.280 --> 0:12:52.680 with varying voltage somewhere to do something else interesting, like 0:12:53.160 --> 0:12:57.040 you could have it go directly to allowed speaker for playback. Now, 0:12:57.080 --> 0:13:01.560 of course, this electric current is really uh there are 0:13:01.880 --> 0:13:04.880 you know, very small elements in your microphone, right, so 0:13:05.840 --> 0:13:10.600 it cannot produce an incredibly strong electric current. So typically 0:13:11.200 --> 0:13:14.520 you would first pass this electric current through an amplifier, 0:13:15.040 --> 0:13:17.840 which increases the strength of the signal. I'm not going 0:13:17.920 --> 0:13:20.560 to go into how amplifiers work. I've talked about in 0:13:20.640 --> 0:13:23.720 other episodes, and it would mean that this this episode 0:13:23.760 --> 0:13:25.760 would go like an hour and a half long if 0:13:25.760 --> 0:13:28.640 I were to to dive into that. The important thing 0:13:28.679 --> 0:13:32.839 to think of is that amplifiers take incoming week signals 0:13:33.200 --> 0:13:36.680 and then push out a stronger version of that same signal. 0:13:36.760 --> 0:13:40.760 Assuming the amplifiers working properly, then that signal could go 0:13:40.880 --> 0:13:44.360 to a speaker and you would have the same process 0:13:44.400 --> 0:13:47.000 that you had with the microphone, only in reverse. The 0:13:47.080 --> 0:13:51.600 speaker also has a voice coil inside it, a coil 0:13:51.760 --> 0:13:56.040 of you know, conductive of metal wire, and also a 0:13:56.040 --> 0:13:59.920 magnet inside the loudspeaker. So the incoming current goes to 0:14:00.120 --> 0:14:02.920 the wire, and we know by the laws of electro 0:14:02.960 --> 0:14:06.960 magnetism that this means the flowing current through the wire 0:14:07.000 --> 0:14:09.280 will also produce a magnetic field. I mean, this is 0:14:09.320 --> 0:14:12.839 how electro magnetism works, and that this magnetic field will 0:14:12.880 --> 0:14:16.439 then pull and push against the magnetic field generated by 0:14:16.480 --> 0:14:20.080 the permanent magnet that's already inside the speaker, and this 0:14:20.160 --> 0:14:24.240 in turn creates the force that pushes and pulls the 0:14:24.400 --> 0:14:28.600 cone inside the speaker that connects to another diaphragm. This 0:14:28.680 --> 0:14:31.480 is a much larger diaphragm than the one that's on 0:14:31.520 --> 0:14:34.280 the microphone on the other side. Right, Because you've boosted 0:14:34.280 --> 0:14:37.360 the electric signal, it can then have enough power to 0:14:37.520 --> 0:14:41.120 move this larger diaphragm. So this larger diaphragm begins to 0:14:41.120 --> 0:14:43.640 move in and out, and it's pushing and pulling air 0:14:44.200 --> 0:14:49.960 and it's just recreating the acoustic pressure waves that we're 0:14:50.120 --> 0:14:53.040 used to go into the microphone and generate the electric 0:14:53.040 --> 0:14:55.360 signal in the first place, so you're kind of preserved 0:14:55.560 --> 0:15:00.800 this experience from sound going into a microphone. The microphone 0:15:01.080 --> 0:15:06.120 as a transducer, transforming that acoustic pressure into an electric 0:15:06.160 --> 0:15:10.520 current with varying voltage, sending that to an amplifier, and 0:15:10.560 --> 0:15:13.760 then a speaker, which then does the opposite. It's also 0:15:13.760 --> 0:15:17.200 a transducer. It takes this electric current with varying voltage 0:15:17.480 --> 0:15:20.520 and converts it back into acoustic pressure and we get 0:15:20.520 --> 0:15:24.680 the playback. That's an analog chain from start to finish. Now, 0:15:24.720 --> 0:15:27.160 if you've got a good quality microphone and a good 0:15:27.200 --> 0:15:31.160 amplifier and a good speaker, you can transmit sound pretty effectively. 0:15:31.560 --> 0:15:34.120 And because the whole process is using that continuous and 0:15:34.200 --> 0:15:39.120 varying signal, it is analogous to the experience of hearing 0:15:39.160 --> 0:15:43.200 the sound itself. We've transformed the energy from one kind 0:15:43.240 --> 0:15:49.200 to another, but apart from that, it is an unbroken chain. Now, 0:15:49.240 --> 0:15:53.640 analog media includes stuff like magnetic tape and vinyl records, 0:15:54.160 --> 0:15:58.360 which are produced in a way where you are transmitting 0:15:58.400 --> 0:16:02.520 analog signals and they are effectively carved into a surface 0:16:03.320 --> 0:16:07.000 that then can be picked up with a stylus on 0:16:07.120 --> 0:16:10.920 a turntable and then converted back into an electric signal 0:16:11.000 --> 0:16:13.800 that then can be sent to speakers. So either way 0:16:14.240 --> 0:16:20.000 you are preserving that analog signal with magnetic tape. You've 0:16:20.000 --> 0:16:22.320 got a recording device set up that takes that varying 0:16:22.320 --> 0:16:26.320 electric signal from the recording and then creates a magnetic 0:16:26.440 --> 0:16:30.920 field with the the writer the right head. Uh, And 0:16:31.000 --> 0:16:33.760 you've got a little electro magnet in this thing, and 0:16:33.840 --> 0:16:38.120 that magnetic field rearranges particles that aren't a strip of 0:16:38.320 --> 0:16:42.000 plastic tape. That's how cassette tapes work. That's all VHS 0:16:42.080 --> 0:16:46.160 tapes work. So attached to this strip of plastic that 0:16:46.400 --> 0:16:50.040 is the actual tape in a tape, are these tiny 0:16:50.120 --> 0:16:53.920 magnetic particles that are bound to that plastic. And by 0:16:53.960 --> 0:16:56.640 applying the magnetic field to the tape, using in a 0:16:56.640 --> 0:16:59.520 tiny electro magnet, you can change the direction that these 0:16:59.560 --> 0:17:03.840 particles are facing on the tape itself. So this process 0:17:03.920 --> 0:17:07.280 arranges particles on magnetic tape in a specific way to 0:17:07.440 --> 0:17:11.360 record that original electric signal you were using. The magnetic 0:17:11.400 --> 0:17:15.000 particles represent the original signal and then in turn represents 0:17:15.000 --> 0:17:18.320 the sound that was used to generate the electric signal 0:17:18.480 --> 0:17:21.200 during the recording process. So when you play a tape back, 0:17:22.160 --> 0:17:26.400 the tape passes underneath an electro magnet at a distance 0:17:26.440 --> 0:17:29.280 that's close enough that the electro magnet is picking up 0:17:29.280 --> 0:17:32.600 the magnetic fields of all those tiny particles, and the 0:17:32.680 --> 0:17:35.960 particles have been arranged in patterns because of that, you know, 0:17:36.040 --> 0:17:39.960 recording process, right. So the fluctuating magnetic field that is 0:17:40.040 --> 0:17:43.080 created because these particles are now passing by an electro 0:17:43.160 --> 0:17:47.800 magnet are again reversing that process. The electro magnet starts 0:17:47.840 --> 0:17:50.919 to generate an electric signal because of that magnetic field, 0:17:51.400 --> 0:17:53.600 and then can go to an amplifier and then go 0:17:53.640 --> 0:17:55.960 out to speakers. So again we use a lot of 0:17:56.000 --> 0:18:00.480 transformational processes to record this sound, right, because you're in 0:18:00.520 --> 0:18:05.080 this case, we took pressure waves, vibrations, The sound went 0:18:05.080 --> 0:18:08.360 into a microphone, creates an electric current with varying voltage. 0:18:08.480 --> 0:18:12.840 That electric current then goes to a tape recorder essentially 0:18:13.359 --> 0:18:17.560 that uses magnetic fields to record onto tape. We take 0:18:17.560 --> 0:18:20.639 that tape, we put that tape into a tape player, 0:18:21.160 --> 0:18:25.879 and that magnetic record then produces an electric current in 0:18:25.920 --> 0:18:28.760 our tape player, which goes to an amplifier and then 0:18:28.800 --> 0:18:31.240 goes to drive speakers and replicate the sound that we 0:18:31.320 --> 0:18:33.920 record in the first place. So again we transformed things 0:18:34.000 --> 0:18:41.200 multiple times, but the analogous sound process has remained stable. Now, 0:18:41.400 --> 0:18:44.560 there's a lot in this process that I have not covered. 0:18:44.760 --> 0:18:47.480 The equipment and methods you use in recording and playback 0:18:48.080 --> 0:18:50.240 determine whether or not the copy you have is a 0:18:50.320 --> 0:18:54.200 really like accurate representation of the original sound like does 0:18:54.240 --> 0:18:57.560 it sound like you were actually there? Or is the 0:18:57.640 --> 0:19:00.320 nuance lost? And the same is true for a back. 0:19:00.400 --> 0:19:04.119 Playback on a really sophisticated system will likely sound better 0:19:04.320 --> 0:19:07.920 than one that's played on some super cheap stereo. Though 0:19:08.280 --> 0:19:11.080 pretty quickly you do reach a point where the returns 0:19:11.240 --> 0:19:14.520 are harder to detect, right like where you might listen 0:19:14.560 --> 0:19:16.640 to something on a good system, and then you might 0:19:16.680 --> 0:19:19.720 listen to that same thing on what's considered like the 0:19:19.800 --> 0:19:22.800 highest of high end systems, and you might not be 0:19:22.920 --> 0:19:26.000 able to tell a whole lot of difference. But the 0:19:26.040 --> 0:19:29.119 basics for analog recording and playback are all there. Now. 0:19:29.200 --> 0:19:32.200 When we come back, we'll talk about the digital approach, 0:19:32.480 --> 0:19:42.720 but first let's take a quick break. Okay, So now, 0:19:42.760 --> 0:19:45.959 we've got an idea of how the analog process of 0:19:46.040 --> 0:19:49.880 recording and playback works. We transform stuff, but we still 0:19:49.920 --> 0:19:53.960 have a continuous signal that represents sound, which is, you know, 0:19:54.000 --> 0:19:57.959 a continuous phenomena as sound changes, as the pitch and 0:19:58.040 --> 0:20:01.120 the frequency shifts, or as the volume changes, or as 0:20:01.160 --> 0:20:05.080 different instruments or voices produced sounds. All those subtle and 0:20:05.160 --> 0:20:08.680 maybe not so subtle shifts are part of that recording method. 0:20:09.040 --> 0:20:13.840 It's an unbroken wave. Digital recording uses a different approach 0:20:14.119 --> 0:20:17.760 in a way. Digital recording is like taking snapshots of 0:20:17.800 --> 0:20:21.480 what is going on during a recording session. And I 0:20:21.560 --> 0:20:23.720 thought of a kind of goofy analogy to sort of 0:20:23.760 --> 0:20:27.119 explain what I mean. So imagine for a moment that 0:20:27.200 --> 0:20:30.720 you are in a soundproofed room and you cannot hear 0:20:30.760 --> 0:20:34.760 anything that's going on outside of this room. However, you 0:20:34.760 --> 0:20:37.200 do have a little panel like almost like a hatch 0:20:37.440 --> 0:20:39.959 in this room, and it happens to be facing a 0:20:40.000 --> 0:20:43.840 really big orchestra pit, and the orchestra is playing. And 0:20:43.880 --> 0:20:45.600 you know this because there's a light in the room 0:20:45.640 --> 0:20:47.439 that lights up when the orchestra is playing. But you 0:20:47.480 --> 0:20:50.960 can't hear anything because the rooms sound proved However, next 0:20:51.000 --> 0:20:52.840 to the panel is a button, and if you press 0:20:52.880 --> 0:20:55.280 the button, the panel opens up, but only for a 0:20:55.320 --> 0:20:58.560 split second. Next to the panel, you have a table, 0:20:58.680 --> 0:21:01.080 you get some paper, you got a pen, and your 0:21:01.200 --> 0:21:04.560 job is to press the button, listen for that split second, 0:21:05.000 --> 0:21:06.959 and then write down what you think is going on 0:21:07.040 --> 0:21:10.480 in the orchestra. You know, like you could write down 0:21:10.560 --> 0:21:15.840 everything from the specific instruments that you're hearing, the relative 0:21:15.920 --> 0:21:19.359 volume of those instruments, any sort of harmonies you're hearing. 0:21:19.640 --> 0:21:23.080 Maybe you're even just trying to play name that tune. Now, 0:21:23.160 --> 0:21:26.360 let's say there's some other rules in place too. If 0:21:26.359 --> 0:21:28.440 you push the button, you are not allowed to push 0:21:28.440 --> 0:21:31.680 it again until five seconds have passed. So every five 0:21:31.680 --> 0:21:34.919 seconds you get another instant of sound as the panel 0:21:34.960 --> 0:21:39.080 opens and closes. This is that little snapshot of what's happening. 0:21:39.080 --> 0:21:43.240 It would be really hard to accurately describe the music 0:21:43.320 --> 0:21:46.640 because you wouldn't have a lot of information to go by, right, 0:21:47.119 --> 0:21:50.360 you would just have this instant of sound every five seconds. 0:21:50.520 --> 0:21:53.119 It might as well be noise at that point. But 0:21:53.240 --> 0:21:56.480 then let's say we start to decrease the delay, where 0:21:56.600 --> 0:21:59.000 you get to have the panel open so that you're 0:21:59.040 --> 0:22:03.960 getting these instants is of sound more close together. As 0:22:04.040 --> 0:22:06.200 that gets closer and closer, it will start to sound 0:22:06.200 --> 0:22:10.600 more like uninterrupted music. Maybe we even rig up the button. 0:22:10.640 --> 0:22:13.120 We tape down the button so it's always pressed down, 0:22:13.560 --> 0:22:15.600 and the panel still has to open and close, but 0:22:16.040 --> 0:22:19.240 it can open immediately after it shuts, so it's effectively 0:22:19.280 --> 0:22:22.840 a shutter. At a fast enough rate, you wouldn't necessarily 0:22:22.920 --> 0:22:26.359 even notice the shutters effect on the music. To you. 0:22:26.560 --> 0:22:30.240 It would sound unbroken if it were fast enough, And 0:22:30.280 --> 0:22:33.600 then you could accurately describe the music you could write down, 0:22:34.040 --> 0:22:35.919 you know, depending on how quickly you can write, you 0:22:35.920 --> 0:22:39.080 can write down a really accurate explanation of what is 0:22:39.080 --> 0:22:42.080 going on with the music, or maybe you're just identifying 0:22:42.320 --> 0:22:46.040 what pieces playing. But uh, you know, in this case, 0:22:46.200 --> 0:22:49.000 if you've got that shutter going at a high enough rate, 0:22:49.720 --> 0:22:53.080 it's almost like you're not in a soundproof room at all. Well, 0:22:53.160 --> 0:22:57.800 this kind of is how digital recording works. So rather 0:22:57.840 --> 0:23:02.760 than preserving an unbroken sign Knoll, the digital process breaks 0:23:02.840 --> 0:23:07.160 up a signal into discrete units. It has to because digital, 0:23:07.160 --> 0:23:10.040 when we get down to it, we're talking about binary 0:23:10.160 --> 0:23:14.320 data zeros and ones. You cannot use zeros and ones 0:23:14.880 --> 0:23:18.560 to uh to to do anything other than talk about 0:23:18.760 --> 0:23:22.320 discrete units. It can't be a continuous thing. Now. As 0:23:22.359 --> 0:23:24.400 I mentioned earlier in this episode, there are a lot 0:23:24.440 --> 0:23:27.680 of quantifiable elements we can look at when it comes 0:23:27.720 --> 0:23:30.800 to sound. We can describe how loud it is, or 0:23:30.840 --> 0:23:34.320 what frequency or pitch it is. We can describe the 0:23:34.359 --> 0:23:36.760 timbre or quality of the sound. That that kind of 0:23:36.760 --> 0:23:39.360 gets us into areas that are a little less concrete 0:23:39.400 --> 0:23:43.480 at least in human language and digital equipment like computers 0:23:44.119 --> 0:23:48.359 are pretty good at handling things that are discrete and quantifiable. 0:23:48.520 --> 0:23:52.480 This is the realm of computers. And remember, ultimately computers 0:23:52.480 --> 0:23:55.360 are relying on those zeros and ones to describe everything. 0:23:55.680 --> 0:23:58.159 Just to be clear, to get to this point, we 0:23:58.200 --> 0:24:01.600 would need to use an analog to digital converter, but 0:24:01.640 --> 0:24:04.720 I'm actually gonna circle round back to that later on. 0:24:05.000 --> 0:24:07.040 For now, we're just going to focus on the basics 0:24:07.040 --> 0:24:11.119 of digital recording because understanding that makes the whole you know, 0:24:11.320 --> 0:24:14.600 a D C and d a C stuff way more 0:24:14.600 --> 0:24:18.960 easy to understand. So, the way digital recording systems work 0:24:19.440 --> 0:24:23.960