Alright lady, what is this everybody? It's a tornado warning here in New York state But we're gonna stay nice and dry and doors and get started with a show and tell the most fun You can have for 30 minutes without getting wet. It's me. Lady Ada with me Mr. Lady Ada were in the Aida fruit factory in downtown Manhattan, which is there's lightning lightning There might be a internet internet disruption if there is we will immediately try to get back online But if not, don't worry It's it's the planet is trying to send us some subtle messages. It's Maybe we should look into some things Let's check in with some people from didgeridoo key and from Aida fruit and also from the community to see what they're up to Kevin did you key? You're up first. Okay? How are you doing? I'm doing good. I'm glad to see you guys are safe and the the lightning storm Yeah under storm We finally got rain. We hadn't had rain all summer in Minnesota, which is very odd Our lakes are starting to dry up. There is only like 9,000 lakes instead of 10,000 There seems to be a it's either there's a drought or it's a flood now like pick pick one sometimes the same week Yeah, you know, it's really upsetting. It's the first time in my life that they have banned campfires You know, it's really too bad. All right. Well, so what I'm showing is I showed you a little bit of a digital campfire now You know, I should have done that I should have created a campfire on this Matrix portal instead of what I did. Yeah, you can still do that Yeah, we talked a lot about air quality last week And I spent more time than I'd like to admit researching air quality after realizing how quick my when I start talking You can see the numbers jump up just for me talking and getting close to this It's pretty amazing and then I decided to take this thing and add it and get it internet enabled So it's now reading the time off the internet and I'm planning on continually adding things to this I want to have weather on here so I can tell if it's a thunderstorm like you guys are having or you know It's just one step at a time But air quality seems to be a big thing these days and it's it's really interesting to read How important it is and how quick just co2 can fill up a room if you're just talking Yeah, well, this is you know, if you can't measure something you can't approve it But now you you're measuring something real time so you can actually improve it. Yeah It's it's insane like even now just setting it down it already dropped down quite a bit And if I start talking into the sensor that it'll fill up and Yeah, it sounds like almost no air movement in your room. Yep Okay, so I did a little research and I kind of revamped my room I added more a bigger area intake and you know made sure the vents were open instead of closed and It was really really interesting what you learned from a project that you were not planning on learning Yeah, and and luckily there's not a global airborne virus that Luckily very true. Yeah, but no, this is a side effect Well, there's a good thing with this So we use these air sent we use the same ones. This is a different project and in places that are Have good ventilation and transmission rate is lower Co2 is one of the things that you can look at if there's not a lot of people in a space There's probably not going to be as much co2 and so it's it's it's a way you can't do like You know, COVID testing and the air are quite yet Um, but you could do this Yeah, it's pretty cool. All right. Thanks so much Kevin. Thank you Kevin You guys have a good night. Thank you. See you stay safe. All right next up Let's go to Dylan and then after Dylan will go to Melissa Dylan. Hello, Dylan. Take it away. How you doing? Hey, I'm doing well I have a few things or two things to show Yeah, first, um This which is the little thing I made. Um, or I didn't make it. I designed it. Um but You can it essentially lets you put A keyboard on top of your. Oh, that's a good idea. That's a good idea. Um, well, okay It's not my idea. I stole it from like some Japanese company, but like good stealing. I used to know that Um, I also made one in aluminum because I kind of feel like it like kind of Looks a bit better. Good artist borrow great artist steal and share on show until nice um, and then we also have um, these I made some coiled cables with the like yca connectors that were um Recently stocked in the Adafruit shop Um, a blowtorch may or may not have been involved and I may or not may not have been blowtorching.  So like air quality is the theme Apparently your qualities solves all problems All right. All right. Looks great. You got all sorts of key projects going on. Nice work. Thanks. Thanks so much Dylan All right. Next up. Let's go to melissa. Hey melissa and Melissa Yes, uh, so I've been working on this code editor. I um Took one that scott had actually done and it didn't really have much of the way of style to it and I've been applying this new one and so I have a That's good. Um a clue connected right now So I'm just going to hit connect because I previously appeared it And then I'm going to hit bond and so that'll go ahead and load this and it'll load all the code that's on it currently And then we can also go to the serial to see there And I have it so like you can go ahead and resize it to all sorts of uh, that's nice. This looks great Is there anything browsers can't do? Uh currently I was working on the buttons up here and they're not currently Functional so I'm going to probably just uh Comment those out, but it'll work as it currently was working Which was it would just kind of save the file as you edited it All right. Well looking forward to uh trying this soon Nice work. Thanks. Thanks so much. Melissa. All right. We're going to go to john park next jp How are you doing? Hey, I'm doing well. Thanks. Uh, so I just put out a guide on this little guy It's uh called the deluxe four by four neopixel keypad and it uses this really nice aluminum Keypad case that we have I've got a qt pi m zero in there running some arduino code And this is uh keeping a tempo of 120 beats per minute right now that'll send out little midi clock signals to things And then I'm just using it to run a software synth But the nice thing is you can put like a couple of octaves of a particular key that sounds good. So I like that's really clicky it kind of goes with like the The vibraphone it is. Yeah, you're right Little percussive element to it. So yeah, uh, so that guide is out and uh, you can grab that you can do anything You want with it. Of course, it could be uh usb hid stuff usb midi stuff Non usb things you could make some little tic tac toe games on there with the leds, I suppose if you want but it is uh It is a good project for people who want to grab our ortho snap apart keypad and then Place it into a nice case and hook up a little qt pi to it. I like how you made it really easy It's just like you just snap into four by four and because everyone uses the same spacing about 0.75 inches It's like just fits It just fits and uh, I was really impressed because there was something you had said at one point that you had done And with the design which is when you snap off a whole column the Neopixel line and uh continues to yeah No, it does exactly as long as it's it's rectangular or square that you don't have to jump or anything It'll actually do the right thing by by weakly passing the neopixel signal down Um, you can sort of see the design. It was a little bit of a a little bit of a hack, but I thought it was um It kind of does the thing that you want it to do I don't think you realize how That isn't what most Um ortho pads do like usually you do have to do some jump ring But I really wanted I wanted to do it so it's like you can have the minimum number of wires possible Very easy. Yeah, we're great. In fact, I have it open open in the back So you can kind of see the the the wires so Whoa, so the only wiring I have is Rose columns rows are in blue columns are in yellow. There's a green line there Which is my one neopixel line and the rest of it's all PCB and then power and ground. Yeah. Yeah Yeah, I hope people, uh, you know pick these up and and use them to make um pads I'm also going to do you know a version that maybe that already has like a footprint for like a you know a keyboard um Break out, but you know, I'm going to revisit this design this design took so long It was so tedious because you know what any change I made I had to change 30 times Yeah, this design took way longer than I wanted All right. Good work. We're gonna be playing some of the videos that you did during the week on ask an engineer tonight And this also, uh, kind of looks like a night writer prop to like oh, yeah Yeah, man, that was fun to do the little larson scan Yeah, and you can have the musical stylings of David Hasselhoff, okay This website's free everybody All right, thanks so jerry All right next uh Name Pedro. Hello Hey guys. Hello everybody. Here's what we have this week. All right. So this week, uh Still ramping up through the halloween prop project So this was a request from phil you'd really like suicide squad and our task was to build the rat catcher's wand or Communication device and the hard part about this was it I think it was in like three scenes in the entire movie So I had like literally three shots to get of it and most of them she's always covering it up or it's like completely There's like rats. Yeah, there's rats or there's like dirt all over. I think it looks really great That looks exactly, you know, sometimes it's like making a prop look like the movie. It's You know part. I mean again, their thing doesn't work either. It's not real You know, it's a prop also So as long as you can get it to the point where it's recognizable. I mean when I saw it I was like, oh, yeah, this is it Yeah, I really like how they had like the jst wires all hanging out So it was like, oh cool. I get to incorporate that and I don't have to hide it, but yeah, it's all Yeah, they probably built it the same way you did. I mean like Just for yeah, just so for folks know and then also Disclosure by the way, we have nothing to do with dc or marvel or suicide squad or anything We have the movies we happen to like the movies once and all But we saw our stuff in the suicide squad. They used one of our boards And we had a little segment on that before but then when we saw this we're like, oh, this is a really cool project To show people that if they see something in a movie Not only could they make that But um, you know, there's entire careers now just making things for cinema and a lot of these Media places use our stuff. So this was a combination of all that. Yeah, what anyways, we never we don't get paid to do this We had to pay to watch the movie Yeah, I wouldn't be surprised if they used a bunch of the same components Which is literally just a circuit playground express and the 2200 uh, cylindrical battery I like the simplicity of this I'd like I like no solder prop projects, you know, I mean like That's it's I know that it's you know, that's not there there's more elegant ways to build this but I I do like um I do like it and I think you know, it's funny that you The the ball and the circuit playground express fits perfectly in it And I also like that it only shines out the end. I actually kind of like that a little bit Yeah, I kept looking at the scenes thinking. Oh, do I have to put like a ring on the back? But in the end it's like, oh no just use like a the filament that'll diffuse it Yeah, I like it just it seems very directional. I think it's I think it's cool Yeah, so we talked about all the CAD on our 3d hangouts and then you can get all the fusion 360 files Or just the stl if you just want to print it out and a nice little simple assembly You can check out the learn guide for that. All right, great work And we played some of these videos and more on Ask an engineer tonight. That's right. Thanks guys. All right All right, we're gonna go to liz and then we're gonna go to mark liz. How you doing? Good. How are you? Good. What you got going on? Uh, so a couple weeks ago, um, I had bread boarded up a fuzz guitar pedal circuit And I finally did a pcb layout for it Um, so I sent this off to ash park. So hopefully I've been like a week or two Um, but it was cool. I feel like I got to Understand the circuit a little bit more like doing the layout and the schematic and everything. Um, and then on the silk screen I got this, um, like tv white noise Of as a design so that'll be on the back along with the name Kirby I like the kind of like it's curvy But it's like there's curves that don't make any sense and I'm kind of digging that Thank you. Yeah, I I love curvy traces. I don't know why but um Uh, and I tried to keep it really small too like the resistors are actually made so that they'll be standing up for placement um, and Yeah, and I won't like solder the pots like directly to the board like all wires coming out same for the It'll be nice and small. Um, so yeah, it's some of those working on Looks good. All right. Well, good work. Keep at it and keep coming back We'll do once it's also come back. Yeah, once you get the pcb to come on back bring your purple purple tv All right. See later. Liz. Good. Thank you, Liz All right mark place out what you got going on this week. Hey mark. That's good Uh, I finally had time to play around with whippersnapper During ask an engineer a couple weeks ago. I actually quickly set it up And I thought I just wanted to see what I could do with it. So I'm going to adjust my camera down to where My fun house is sitting. Sorry um, so right now it's not doing anything but I'll share my screen and There it goes Um And just to show the power that I found and even the minimal functionality in here right now No code and when I say I had a little time to play with it this took about half an hour Now through a different i o I can start controlling the leds. You can't really see the green one. Yeah. Yeah, we can see him and the blue one and the red one And well, this is cool if you want to turn leds on and off which is always fun um The triggers in a to fruit i o already there Is just amazing. So I've got a lot here all these led tests are all what you're seeing in front right now Uh, but speaking of air quality, uh, you can take advantage of your existing feed So I've got a couple triggers set up that is outside monitoring the air quality right now We've had a lot of smoke fire our fire smoke from the fires around us Yeah, and it's easy to set it if it's greater than 50 then set right now. This is just the onboard led To turn on using multiple leds. So you can have a little warning system is the air good green Uh, I don't actually have a yellow led I found yesterday. Uh, so it's blue Uh and red for bad, but this is all off existing feeds that I had already So I didn't have to Do anything more I could immediately build a little display for indoors And as I said, it took about half an hour of time Yeah, I like that I like mqtt and you know one of the things about it if I know that That we did was like it uses an existing standard mqtt and all these feeds That's subscribed and published to each other and so you can take advantage of the fact that you already have this like published subscribe um set up to Have data come in and move around and do webhooks And it's like it's just raw data. I want to say a little bit of like, you know You know like neil stevensons article, you know is early paper about unix It's like if everything's a text file and you can manipulate everything is text files You can have all these little tools in unix where you can pipe data and move it and filter it and have things Connect to other things and so we're that kind of philosophies, you know What we're trying to do with io where you you have these data feeds that are just really kind of plain text And then you can really easily adapt and move them around because they're they aren't Um, they're like bubbles of data. They're just like raw data like the number is the number It isn't like a number that's encoded in base 64 and a thing that's in an envelope. That's pgp signed It's like no it's a number Yeah, and that's exactly what I found. I didn't I hadn't never played with the triggers before And then all of a sudden I was like wait I can take this existing feed and then feed it into this other service that I've just used and It can trigger something else and yeah It It was so simple. I mean it was too easy Yeah, no way We're definitely going to get the feedback that we make we're make we're making uh air quality sensors and iot Too easy. It's kind of a yeah, that's fine. Um But I think that one of the things too is when people think about the things they want to do And they say it in regular human language io kind of helps you along with that like if this thing Is 50 then light up this led Green And it's like a very it's like oh, I understand what that's doing I understand what that is and I and I there's something in my home That's going to light up after the air quality gets to a certain number It seems to make sense for I think a lot of people Yeah, that's what I found as a intro project is something that's new this works great and it's just And it took almost no time to figure it out and yeah for anyone learning It's a perfect system for beginners. I can get started then for experts are like I do not I'm an expert I don't always my remaining years left because it takes took me so long to become an expert So I want that I want stuff to be easy now Well, it's nice. I've got a bunch of things using it a fruit io today. So now if I want to hook up a Display just indoors to show me. It's not like I have to be like, okay Find this find this and just write the same code you've written in 10 000 times before Yeah, that you can't find anymore because who knows where you saved it. Yeah, so I'll keep giving good beta feedback. Thanks for testing it out and showing this off It's all very new and you know, we're in beta and so anything that you find will help us and we're going to You know, we're going to create the same kind of system We have for circuit python where it's it's there's releases and updates and hopefully people can also contribute So if you have a sensor that we isn't supported you'll be able to contribute the code to it We can you know, I mean there's thousands of different sensors and and we'll slowly get there Um, but we're hoping that the community, you know by having an open standard and having all this code be available Hopefully you can get uh people to contribute the code that they need to finish their projects to work together Yeah, I'm really looking forward to seeing when that's out there All right. Well, thanks mark. Sorry. We made it so easy. Um, I could send you some crummy websites Uh, later if you get frustrated about or something. I have a list I could send it sounds great Thanks a lot. Bye. Thanks everybody. All right. That's that's a wrap. We have uh, you know, sometimes it's short and sweet Sometimes we go over super 10 minutes. We're going to be on uh back with ask engineer at eight o'clock. So stay tuned Yeah, and for longtime viewers We'll probably have a guest on show until next week. So we'll uh, we'll talk about that next week So we'll see you all later ask an engineer starts in about 10 minutes. Thanks everybody. Bye. Bye


So, what we want to do or well look at briefly is what I do in my adaptive control course and this is back stepping adaptive control, okay. So, you already know what is back stepping. So, it turned out that actually the name back stepping I told you right it came from the KKK Kanalakopolis Kokotovich Kristic actually Kristic I guess named it as back stepping the method was sort of known before that so and he is one of the one of the key researchers in the area of adaptive control, okay. So, the entire concept and utility of back stepping came from adaptive control, yeah. So, not the other way around although it seems like we are doing the other way around. So, we already did for the non-linear system case back stepping ideas very powerful, yeah. You can easily construct sequentially CLFs and do a lot of things, yeah. In fact, even automate it if you can I mean you can do symbolic, symbolically keep generating new functions if you do not want to keep track of the complicated terms, yeah. So, back stepping like I said came from adaptive control. So, obviously it makes sense that it is very applicable in adaptive control. So, modern adaptive control is uses a lot of back stepping, okay. So, what is this we will not look at all these I mean what they mean and so on. So, I am not going to sort of worry about this, worry about trying to explain this because this is an adaptive control course so obviously there was more material here. So, back stepping obviously is a method for generating strict Lyapunov functions or the way we said it is control Lyapunov functions, okay. Control Lyapunov functions and strictly Lyapunov functions sort of the same things, yeah. Basically V dot is negative definite, yeah. For any CLF you will see V dot is negative definite that is how it is defined in fact. So, that is what is called strict Lyapunov functions. When you take a V it is nice and positive definite and all that and the V dot is negative definite then it is a strictly Lyapunov function, yeah. And we just saw a spring mass damper sort of example where even though we know that the system is asymptotically stable the V that we designed or chose, yeah did not have a negative definite V dot, okay. So, those are not strictly Lyapunov functions, okay. They usually give trouble in adaptive control. They are not nice for adaptive control, yeah. So, which is why backstabbing is so popular because adaptive control requires CLFs or strictly Lyapunov functions, okay, great. So, suppose we have this non-linear double integrator. We saw a double integrator. Now we have a non-linear double integrator and this is where we have the unknown appearing, okay. You see that this is only one function. This could easily have been summation of theta i star fi plus u, okay. It could have been very easily that. So, that could have been like a function approximator if you may, yeah. So, it does not matter if there is 1 or 10 or 100 and so on. You can still use adaptive control ideas for this, yeah. But this is the unknown, yeah. This would be again, inertias or parameters for identifying the general function, yeah with these f being the basis functions and so on, yeah. But what we want to do is we want to achieve some kind of a tracking for this system. We want to achieve some tracking results, all right. So, that is what I say. So, everything is in real. So, I am keeping the presentation simple, of course. So, everything is real numbers. F is of course a map from the state and the time to the state again, yeah or whatever or the vector, the derivatives again, all right. So, what is the objective is tracking, right. What is tracking? It means that I have a signal r and the position follows the r, velocity follows the r dot because I have this matching kind of a requirement, okay. So, the trajectory also has to satisfy this, okay. The velocity is derivative of position, all right, great. So, what is the dynamics for the errors now? This is what we have been doing for the tracking problem, right. We construct an error, we write the dynamics of the error. What is the error dynamics? Even dot is e2 comes by virtue of the matching condition, right. And e2 dot is just x1 double dot or whatever, x2 dot minus r double dot, right. So, x2 dot is this minus r double dot, okay. So, this is my new dynamics that I am working with, right. I still have an unknown. If I did not have an unknown, I would simply cancel this guy, cancel this guy, introduce the nice terms that I wanted, okay, all right, all right. So, I already say that this is a bad Lyapunov function for this system, right. It leads to what is called detectability obstacle. So, we will try to use back stepping to construct Lyapunov functions here, yeah. Because you know that this is a non-strict Lyapunov function even for the known case, yeah, you have seen the spring master. All right, what do we do? Standard back stepping, right. We have even dot is e2. We assume that the e2 is the control. So, we design an e2 desired. What is the e2 desired in this case? Just a minus k1 even, right.  Then this is a good enough system to follow, okay, all right. So, if I did that great and what would be the corresponding Lyapunov candidate Lyapunov function, it is half even square, right. Because it is half even square and this dynamics, right. I get v1 dot s minus k1 even square, yeah. This is what, yeah. This is for the first stage, for the first system. This is the Lyapunov function, right. Now, I will augment it, right, using the back stepping error and so on. So, what is it? All of this happens when e2 is exactly equal to e2 desired, which is not possible, yeah. We do not control e2 itself, yeah. So, we construct the back stepping error, okay. What is the back stepping error? It is this, e2 minus e2 desired. Because we cannot make e2 equal to e2 desired, we try to drive e2 to e2 desired. This is the idea of back stepping, okay. So, what is e2 minus e2 desired? It is e2 plus k1 even, yeah. And this is why denote as psi 2, okay. This I denote as psi 2, psi 2. So, now one of the questions that I asked, which anyway we also answered in back stepping, I believe, that does this mess with the original control objective. The original objective was to drive e1 and e2 to 0. But now with the new dynamics, my objective will be to drive e1 and psi 2 to 0. So, what happens is that if indeed e1 and psi 2 go to 0, e1 goes to 0 and psi 2 goes to 0. But in inside psi 2, I also have e1, which is going to 0. Therefore, e1 and psi 2 going to 0 is the same as same, e1 and e2 are going to 0, okay. And vice versa, you can check, yeah. Because this transformation is sort of a non-singular transformation. It is a nice transformation, yeah. Nice value transformation of the states, okay. All right, great. So, you have the first state e1 and you have the back stepping error state psi 2. And I take the derivative of psi 2 to find the dynamics, yeah. And I get this guy, yeah. It is just e2 dot plus k1 e1 dot. So, that is this plus k1 e2, all right. Clear? Okay, fair enough. Now, what do we do? What do we add as the new term is the square of the back stepping error, right? Every time when we do back stepping, all we are doing is taking the original Lyapunov function and adding to it the square of the back stepping error, always. This is how we come up with the CLF, right? This is what we proved in our back stepping result, okay. Great. So, what is e2? e2 is half psi 2 squared. And what is e2 dot? It is this guy. Psi 2 times the derivative of psi 2, yes? All right. So, right now, the way this is done is we are not looking at the v completely as of now. So, as you understand, the v for the entire system would be v equal to v1 plus v2, right? We have chosen a control even before we did that analysis. We are choosing a control right from here, yeah. And how do we choose it? Basically, cancel this guy, cancel this guy, cancel this guy. And introduce a good term, okay. That is all we are doing. This is used, this is cancelled, this is cancelled, this is cancelled and a good term is introduced in the psi 2, okay. This control works. Ideally, I would not recommend doing like this. I would say you first do this v equal to v1 plus v2, take its derivative, then guess the control. Okay. So, what is, let us see. What is v equal to v1 plus v2? v1 was e1 squared by 2, right? And v2 is psi 2 squared by 2, right? So, v1 dot is e1 e1 dot, v2 dot is psi 2 psi 2 dot, okay, all right? So, what is e1 e1 dot? E1 dot is e2 and psi 2 psi 2 dot is because of this choice. It is minus k2 psi 2 squared, yes? Okay, because I cancelled everything. All I am left with is minus k2 psi 2, okay, okay, great. Now, I get this variable e2 which is not my variable anymore, right? Because I did a transformation. So, I want to write e2 in terms of the new variable which is psi 2 and e1. I do that, right? Psi 2 is just e2 plus k1 e1, right? So, I have just written e2 in terms of the new variable, yeah? And once I do that, what do I get? I get this nice negative term in e1 minus k1 e1 squared. I already had the nice negative term in psi 2 minus k2 psi 2 squared. And I also have a mixed term, e1 psi 2, right? But I already know what to do with this. We have done this before. We use this, that 2ab less than equal to a squared plus b squared for this mixed term. So, this mixed term is basically going to become less than equal to half e1 squared plus half psi 2 squared, which is this, yeah, okay? So, instead of an equality, now I move to an inequality. That is it, all right? Because I am less than equal to is always fine. We are doing the Lyapunov analysis, right? So, I have minus k1 e1 squared minus k2 psi 2 squared and then this additional term, okay? But that is pretty straightforward. I mean, I can always use k1 to dominate the half, k2 to dominate the half and v dot is negative definite, right? This is what the entire trick of Lyapunov analysis is all about, all right? And once I do that, what happens? I know that I have v dot negative definite. What does it mean for v dot to be negative definite? It means that both e1 and psi 2 are going to 0, right? Whatever is in v, basically v is going to 0. So, whatever is in v, that is e1 and psi 2 are going to go to 0. And we have already proved that e1 psi 2 going to 0 is equivalent to saying that e1 e2 is going to go to 0, okay? So, done, okay? Now, great, excellent, yeah? We have got a strictly Lyapunov function. Why? Because v dot became strictly less than equal to 0, yeah? Unlike if I had taken e1 squared plus e2 squared by 2, instead of e1 squared plus psi 2 squared by 2, I would have landed in trouble. e1 squared plus e2 squared by 2 will only give me v dot negative semi-definite, okay? So, we have something nice here. Now, but there is a problem. In the control, yeah? Although here if you see the way this is written, it is written as theta hat, but you see it says theta hat is theta star. Basically, this is a known case, what we call as the known case. If the parameter was known, you can cancel this exactly, okay? If the parameters was completely known to you, accurately known to you, then obviously you can do this cancellation, yeah? But now we are in the adaptive framework. We do not know this parameter, okay? We know nothing about this, okay? Then what do we do, okay? So, great. So, one nice step is done. We have constructed a CLF, yeah? And this is critical for adaptive control. Without a CLF, you cannot do adaptive control, okay? Remember this, yeah? For the known case, by the way. I am not saying CLF for the entire system after adaptation and all that. I am saying if you, if the, if even when the parameters are known, you do not have a strictly appano function or a CLF for your control system, then you have a problem. You will not be able to use that to do adaptation, okay? So, even in the known case, if it is non-strict, then in the unknown case, it becomes even worse, okay? That is essentially the idea behind detectability obstacle. So, even at least for the known case system, you must have a CLF. And that is why you use backstabbing, okay? If you have a CLF in, by some other means, feel free to use it, no problem. You can guess it without doing backstabbing, no problem, yeah? If you can guess the control appano function without using backstabbing, not a problem. Absolutely feel free to use it, yeah? But more often than not, you will not be able to guess it. All right, great. So, what happens when theta star is unknown, okay? I have already sort of given a glimpse. What we do is instead of theta star, we use what is called theta hat, okay? So, this is the estimate of theta star. This is called the estimate of theta star. So, basically we try to estimate theta star, okay? We do not because we do not know the value. So, what is the best thing we can do? We try to get an estimate. This is what control folks do. What is an estimate? It is like if you have seen Kalman filtering, you have a state estimate, right? You do not have the true state, but you use some sensor data and you feed it into a filter, yeah?   It is not the true state, yeah? Because you are seeing the world through the sensors, okay? So, there is no real concept of true state, yeah?  For example, if I have a bunch of vision sensors, with which I am trying to identify my current location, my current position XYZ position, okay? And I do a pretty good job, okay? But that is still a sensor data, right? But the real, what a lot of folks who do is they would try to compare this vision process data to say GPS data or very accurate GPS data. If you have say military-grade GPS data, it will have some, you know, submillimeter accuracy and then you can compare that, yeah? With your position given by GPS with your vision-based data, okay? So, there is no real true, so all the data everything, you see the world through the data, right? Through the sensors. So, therefore, there is always an estimate involved, yeah? In the states also, in fact, yeah? Although, we do not talk about it in this course, yeah? But so, the idea is here also what we do is we create an estimate for the parameter, not for the state, but for the constant parameter, okay? This is what is the adaptive control idea, okay? This part is called adaptive estimation, but it combines with the control, so it is called the adaptive control. It shows up in the control, all right? Okay, great. So, we replace it with an estimate, we replace the true value as an estimate and then we try to figure out how to calculate the estimate, okay? Because just like in a Kalman filter, there is a particular logic by which you update the states of the Kalman filter, yeah? Comes from some kind of an optimality, right? Kalman filter is basically coming from an optimality result, yeah? So, similarly here, it is not coming from an optimality result, I can tell you. It comes from a stability result, okay? This is also an estimate, typically in deterministic systems that is where there is no probabilistic quantities coming in, estimates or observed states, sorry, actually I would say estimates come from stability requirements, yeah? Not optimality requirements, all right? Okay, great. So, what is the stability requirement? We want to drive the even e to do 0, okay? That is our stability requirement. We want to be able to track even if we do not know the true value of the parameter, okay? Great. Now what? We create a slightly modified candidate Lyapunov function for the unknown case. We already have a strictly Lyapunov function for the known system v1 plus v2. We add to it a term in the parameter error. I do not know the parameter. Best I can do is try to drive my estimate to the true parameter, right? Again, same logic by which most of control folks will work, yeah? What is this? I define this theta tilde. This is a notation that we very standardly use in adaptive control. Tilda denotes the parameter error. Theta star denotes the true value. Theta cap denotes the estimate, okay? Standard in even in nonlinear control for that matter, okay? Now we take time derivative just like we were doing earlier. What is it? v1 dot is even even even dot. So, e1, e2, v2 dot is okay. Now I have to write some terms I guess, sorry. So, if you remember, this is e1 squared by 2 plus psi 2 squared by 2, right?  So, this gamma is some positive quantity. Gamma is just a positive scaling called the adaptation gain, okay? So, basically controls how fast you will update the parameters. That is it, okay? So, if you notice the last term had a negative here. Why? Why does the last term have a negative sign here? Yeah, theta minus theta hat and this is a constant. So, the derivative values to 0. So, this is minus theta hat dot, okay? Simple, alright? Nothing too complicated. Now I am going to write the terms, right? This is e1 dot, e1, e1 dot is e1, e2 just like before plus psi 2, psi 2 dot. Psi 2 dot was what?  And I keep the last term as it is, as it is. Now what did I choose my control as? I chose it to cancel these terms, tried to cancel this term by saying theta hat f x t, yeah? So, these two terms I can still cancel, right? If you see the control, yeah, it is this, right? So, this term will still cancel, this term will still cancel. The nice term will still appear, yeah? But this term will not cancel, right? So, what will I be left with? Correct. So, this is where the theta tilde shows up. This is basically, yeah, that is basically how I get from here too, yeah? Because the control will have a theta hat.  So, theta minus theta hat f is theta tilde f and that is this k, okay? Yeah? Any confusion you can just do it on your own and see, yeah? So, that is it. From here I go to this step, all right? Now what? Now it is not that difficult. Now what do I do? I of course substitute for e2 because I want to write everything in terms of the new variables just like I was doing earlier, right? So, I am left with e1 psi 2 minus k1 e1 square minus k2 psi 2 square. And I do one more thing. I, you see that now this term theta and this term both are theta tilde common, right? So, I take the theta tilde common and I use this theta hat dot to cancel this. I can, if I choose theta hat dot as gamma times psi 2 f, yeah? Absolutely. That is our estimate, right? So, I have just written it here if you see. All I have done is I have taken these two terms and I have taken theta tilde common, right? And this gives me an e, and something in theta hat dot, right? What do I do? I cannot make this negative definite. Remember, I do not know theta tilde. So, I cannot give something like minus k theta tilde or anything like that because theta tilde contains the unknown. That is a parameter error. I do not know it, okay? So, the best I can do is make this 0. That is the best I can do. I will try to make this 0 because I cannot make this negative definite, right? And how do I make this 0? By this choice, okay? Yes, cannot make this negative definite in adaptive control because theta tilde is unknown. Otherwise, you will have to have a minus k theta tilde which is not allowed, right? It is an unknown. So, that is not possible. So, the best I do is I make this 0, okay? So, this is gone. And what do I have here on the right-hand side? You see I have all known quantities, right? Gamma is known to me, some adaptation gain. This is why I said it is adaptation gain because it sort of gives you a rate at which you are adapting. And then psi 2 is the second state. It is just e2 plus k1 e1. So, I am assuming that you are measuring the state. So, you know this. And then f is just some function. Equal thinking in neural networks is just basis functions, some basis functions. So, known to you obviously, even if it is time varying, it does not matter. But it is known to you, okay? So, once you have cancelled everything, you are left with what? k1 e1 square, k2 psi 2 square, e1 psi 2. Notice, v dot looks exactly like the known case. Yes, I started, I mean even though I started with a more terms in v, I ended with the same v dot. This is why starting with non-strictly appano functions will land you in trouble, okay? If only e2 was appearing here, then you will have something like this. This will be a big problem for you, okay? So, in adaptive control, the way we do it, the v dot looks exactly like the known case, okay? So, looks exactly same as known case v dot, okay? Even if you started with a additional term in v, okay? Now, what can you say about this v dot now? Definiteness? Of course, you can do this a, b less than equal to a square b square and all that, right? What about this definiteness? Negative definite? Is this v dot, is this v, so is v dot negative definite? Maybe time you guys make the same mistake. What? I added a new state, theta tilde is now a state. It is not a, right? It is a new variable there. So, v is now a function of three variables, but it contains only two in v dot. It is only negative semi-definite, okay? So, even if you started with a nice CLF with a negative definite v dot, for the known case, as soon as you move to adaptation, your v dot will become negative semi-definite. Why? Because you had more terms in the v, which are new variables, okay? Yeah, this should be very clear in your mind, okay? When you go to the adaptation, you add an adaptive control part, your v dot will become negative semi-definite and that is what I have written here, right? So, the v dot is negative semi-definite, right? So, what does this give you? As always from the Lyapunov theorem, all that you get is uniform stability, nothing more, okay? Then of course, now we are left with trying to use Babelatz lemma and so on. So, of course, you get from this step to this step also using this sum of square type of result, which we have been using regularly, all right?


Hey everyone, good morning. Once again, thanks for joining in. Welcome. I hope you're nice. Thanks for joining. Alright guys, let's pray and we'll get started.  We'll come and have your way. Jesus, even as we learn about ministry and worship ministry, God, I pray that you will continue to pour out your wisdom, your knowledge, your understanding, your insight. Over us, Father. In Jesus' name, amen. Amen. Awesome. Okay, I hope you all are doing well. Today is an exciting class, a more practical, more practical, not hands-on class with Sib. So we look at chapter six in your notes, in your content. All about today is going to be about music and technology, worship and sound and technology used in worship ministry, the importance of it. So you can follow along in your notes, but I'll also share my screen. Oops, sorry. So I'm sure you can all see the image. What I'd like to do is just before we go ahead and start talking about all the gadgets and whatnot, so can any of you share the importance of worship technology in ministry and worship ministry in general? Would you say it's important? Yes, no, maybe. That question is for all of us. How important do you think sound and technology is important in ministry and then in our context when it comes to worship ministry? Yes, okay. All right, so here's the next question. Why is it important?  It depends because I have a friend who knows how to worship. But for excellence's sake, I think it's also important. But for worship's sake, we have to come to a place where we know how to worship, whether it's good or bad. I'm not saying you should not go for excellence. I'm saying that he taught me something very different, whether the sound was good or the sound was bad, he just knew how to connect and worship. So he didn't disturb his flow of worship. Invariably, he comes from a place, or he comes from an altar that has worship. So when we come into a couple of settings, whether it's good or bad, he just connects. He knows how to connect. It depends on everybody from a pastoral point of view, that's only a pastoral fact. With good sound, they flow better. It helps with their grace and their knowledge. Some other people might just don't need the sound. And also under the husband, when he's ministering, he likes sound, he likes the noise. And if it's the wife ministering, she doesn't like this thing. So it depends on different people, have different graces that helps them. Like the prophet said, I need a mistral. So it means for the prophetical at that time, he needed a mistral. The Bible says David was skillful. He was handsome and rude, but he was skillful on behalf. So for different things. But I just learned invariably that most times, in the place you're going for excellence, you should know how to get the core of worship, even from a place of our heart. Right. Thank you, sir. Right. Yeah, thanks, Louis. Yeah, thanks for explaining that so much and so well in detail. Yeah. Okay, Susan shares, lyrics should be clear what they're singing. If it's a large congregation, whole church should be involved in worship. Yep. Yeah, that helps. What is this? Yeah, please talk to me. Why do you think the sound and technology is important for a ministry, for a church ministry and in our context, worship ministry? Feel free to unmute and speak. Christopher, would you like to add anything as in just respond to that? What are your thoughts on sound and technology? Sir, a small thought. Yes, go ahead, Rupa. Sound and technology is also made by God and we are using it to enhance and worship Him with it. And it makes it so beautiful, this sound when it is in harmony and in symphony. It really brings alive our spirits in His presence. It's very useful, this one, for all the whole congregation. All right, yeah, thanks. Yeah, so anybody else? Can you hear me? Yes, go ahead, Christopher. Yeah, sorry. No, I just wanted to add that, I think any industry that has to keep up with the times and digital technology has also evolved so much over the years. So I think it's important to have worship ministry also keep in line with other music industries that are using the latest technology. So I mean, for example, if worship ministry has not kept up to the current times and the technology that is used, then people who hear it may feel that it's not sounding as good as it should. So why not use the best and the latest technology for worship ministry also. That's why I think it's most important. Yeah, thank you. Just keeping up with times, keeping ourselves updated. But also, I mean, I think, if anything, in the last two and a half years, the church has understood the importance of technology in general, overall because of the pandemic, isn't it? This whole online e-learning courses and online classes for Bible college was initiated because we were pushed to a corner and we had to improvise and thank God for technology. It's made it possible for us to connect with so many beautiful people from all the different parts of the world, isn't it? So there's technology involved, so many things that goes into it, and then there's sound is also involved, isn't it? The clarity. So for us to understand each other, it's one thing to connect and it's another thing to just being able to be very clear and what you want to convey, isn't it? So that in general, I think, I would say it's very important. And so another important, it's very important for churches to understand the importance of it, especially most of our churches in India, I mean, we don't seem to have a budget set aside for sound and technology. Investing in sound and technology has seemed like investing in a liability and not as an asset. Is it worth the investment? Should we have a budget to invest in a good sound equipment and whatnot, right? So there's that kind of a mentality, at least from the churches that I've come and grown up or seen as well. So we'll have to wait for a while before we could get a gadget because it seemed that it was not worth it. So that's the whole point of this chapter, at least, is the importance of the sound equipments, the technology and why we need to keep ourselves updated, right? So here are some of the things that, see, if you absolutely have no idea about sound and technology, you're not technically savvy when it comes to all of these equipments and some of the gears that we will be talking, it's absolutely fine. Okay, so don't get too overwhelmed by some of the technical words that might be used in this session. But these are some of the basic things that you will have to keep in mind if you're leading a worship ministry or if you're leading a ministry and you have a worship pastor under your supervision, right? So just so you understand the language that is being used, right? So some of the terminologies that will be used so you need to be aware of certain things. That's very important. So there are many things to consider, but first thing that we talk about or that comes to mind at least when we talk about sound is the microphone. Microphones, right? So what it does is when you speak, the volume is amplified, isn't it? So this is one of the examples of the microphone that you are seeing in the picture. It's from a brand called Shure, S-H-U-R-E, and the model number is SM58. So before I continue, go ahead, I want to also do something a little different in this class or this for this chapter is I also have my colleague, Rohit, who we worked together at APC. He's a sound head, so to speak. So he's in charge of all the sound and technology that goes behind it. And if you are able to hear the live streaming of our online services clearly, it's because of this dude. So I thought I would have him over for the session as well. He can add some of his insights, his thoughts, and if you have any questions, you can also post it in the chat section. So we'll have like a Q&A kind of a session and something kind of an impromptu kind of a class today. Yeah, I hope that's all right. So we have microphones. So very quickly, Rohit, what are some of the different kinds of microphones that one should be aware of? Basic idea. So what you see as SM58, that comes under what kind of category. I know there are different categories of mics. So for the most part, I think the most common is a dynamic mic and a condenser mic. So dynamic microphones are mostly used for vocals and condenser mic is used for instruments. Instruments or if you're going to record vocals, it'll have to be in a very controlled environment like a studio setting. So you get very clear vocals. So the main difference, a condenser mic is more sensitive. But those are the two broad categories that you will see anywhere you go. So one is the dynamic mic and the other is the condenser mic. Yeah. Okay, so condenser mic, I mean, you see it cap, it's more easy for it to capture all the other sound that's happening in the environment. Is that what it does? It's more sensitive. It picks up a lot more. There's a lot less rejection. A dynamic mic only picks up something that's close range. Like a condenser would be, you would use it for like a choir. Use it like you would have seen mics used for symbols. So it picks up everything in that range. But a dynamic mic, anything further than like a foot and you'll probably lose it. So the mic in the image is that's a dynamic mic. It's very directional. So you have to point it at the right direction so it picks up the sound. Is that it? Okay. The condenser is the one that, okay. All right, cool. Right. So that's what a microphone is. We've all seen one. We've all used one. Okay. And the other thing, after the microphone to add to the sound arsenal, so to speak, is this mixer board or mixer, you know, also known as, they come in all different shapes and sizes. You would have seen these huge ones in big studios and concerts and whatnot. Right. Christopher, I see that you raised your hand. Oh, yes. No, I just want to, just from the mic, I just want to, I just confirm that, you know, the mic that is used by, for example, the pastor, you know, when he's doing the sermon, the one that's on his, you know, connected to his face, that would be a dynamic one. Is that correct? That's actually a condenser. That's a condenser with a unidirectional pickup pattern. So it doesn't pick up too much. Okay. What's the reason why, why, I mean, we just know you mentioned that a dynamic one is very focused on the voice, because it's very close to his mouth. Wouldn't it be, wouldn't it need to be a dynamic one? I'm just curious. Okay. So condensers give you better clarity. So as you go further advanced in the chain, there are people who have made directional condensers as well, because why not benefit from the extra clarity, right? So that's one variant of a condenser. Okay. But as a baseline, that's why I said dynamics as a baseline are very unidirectional and close range more importantly. Yeah. Okay. Thanks. Yeah. Thanks, Christopher. Yeah.  For example, you see at least three microphones, three vocalists and drums, then the bass guitarist, electric guitarist, acoustic guitarist keyboards. And so there are at least say, let's say 10 of them on the stage, right? And you see all wires going through their instruments and all these cables running on the stage. And they all need to go somewhere and get connected, isn't it? So it's not just cables on the stage going behind the stage endlessly. And so all of those cables are routed to this device, a thing called a mixer. And this is where all your, your mics are connected, the instruments are connected and whatnot, right? So, and they come in different shapes and sizes, as mentioned, you know, it could, and they have different channels, channel numbers. So for example, the one that you see here, it's I think 16 channel mixer. That means you can go up to, you can connect up to 16, say, it could either be a mixer of microphones and instruments. Is that right, Rohit? Yeah. So either instruments or microphones, depending on what the source is going to be. Yeah. Right. Okay. And yeah, you're also seeing the image, another smaller mixer there. So again, it depends on the size of your congregation also, right? And, and the budget that, that the church is willing to invest in a mixer board. So this is very crucial, very essential. What, so what this does is not just, all the instruments are connected, are getting connected to this device. But if you see all these knobs over here, okay, Rohit, do you want to explain to, you know, this, what these knobs do, from the small one, so like a basic mixer that has. Yeah. Okay. So primarily you will have your inputs. So either, either a microphone or an instrument goes in there. Then you, the next level would be you setting your signal strength. So setting up, setting up enough, enough so it's heard, because that'll be like first stage of amplifying the signal that you get from the microphone. So you have enough for the mixer to manipulate. Okay. Then, you have the equalizer, which is used for tone shaping whatever source you have. So a good reference of how, how you wanted, how do you want to tweak those knobs is, how would it naturally sound? Like we know what our own voice sounds like, or what an acoustic guitar would sound like. So if through your speakers, it does not sound like that. Then you use the equalizer, you'll have maybe two or three knobs in a small, small format mixer.  But on a very basic level, your low frequencies, mid frequencies and high frequencies. So you tweak them based on how, how you know it should sound. Basically that's, that's the very base reference of how you manipulate that. Then, and then the volume down. So that's, that's very bare bones of power mixer. Every mixer that has these things. Yeah. Yeah, thanks Rohit. So, okay, just for clarity sake, I mean, I'm not sure some of you have, I said, I'm not sure if you got a little freaked out with the words, terms like a frequency and all of that. It's nothing guys. So how many of you have, what is it, a music player at home? I'm sure most of you have like a music system at home. I mean, basically the days when I used to go up, it looked, you have these, the highs, the mids and the lows. I mean, the treble, the mid and the bass in other words, right? The treble. So, and that's what basically what the mixer also does is, and you can control the treble like how, you know, treble should be wanted to sound and how bassy you want the sound, the song to sound and that's what the mixer does. And in the image that you see all these things here, those are called as faders, that you can increase the volume or decrease the volume by pushing it up and down. Right. And then you, in this small mixer that you see over here, these three blue color ones, knobs, the top one is that is, which increases or decreases the treble, the high frequencies that sounds very, like screechy kind of thing. It controls that frequencies and then you have the mids and the lows, the bass. You can increase or decrease the bass. It depends on how much you want because these are all just FYI. Okay. And then this is basically what this mixing console does. Okay. That's what a mixer is. Say I saw that you raised your hand. Did you have a question? Yeah, you've clarified it. I just wanted to ask as basically in summary, you're saying this controls the outputs of whatever sound you want to hear. Okay. Thank you. Correct. Yes. And it does a lot more as well. Like it has effects, like in this, in this bigger mixer, mixing console that you see, you see there are additional knobs over here. It has all these effects such as reverb and delay. Like for example, if you want delay, delay is one of the effects that says, how do I demonstrate? When you say hello, and then hello is repeated, like hello, hello, hello. That's a delay effect. You hear in all these, at least in India, Bangalore orchestras that plays in the, you know, on the roads. And it's their favorite effects. But anyway, so that's what a mixing console is. Abraham, I see, are we going to need another device attached to the mixer? Or we can, or we can just connect directly from the mixer and get the best sound. I'll let Rohit respond to that. Rohit. The airborne's a basic setup. Microphone to mixer, mixer to speaker. That's about it. But I think as you scale up, let's say you want to use multiple speakers, you'd have, let's say a splitter of sorts. So there'll be one more device between your mixer and speaker so that it splits to multiple speakers. Let's say you have a speaker outside your hall, one on this side, one on the balcony. So that's one more thing that could come between, before it reaches the speaker. So mixer to a splitter or a speaker processor and then the speaker. Yeah. Okay, alright. Thanks Rohit. Everyone, what do you mean, please to those online? Yes. Yes, I did confirm that is it okay to connect from the mixer directly to a laptop to those online or you need a device so that you could at least get a correct sign for those online? You can, you can connect directly also but the recommended route would be to get an audio interface. Yeah, like a two channel audio interface. I think just later in the presentation there's something about that as well. It's for recordings and stuff. So you take an output from this, go into that. It's basically it'll look something like your set up box for your TVs or like a router, internet router goes into that, a USB cable comes out and plugs into your computer and that goes to zoom or YouTube depending on what you're doing. Okay, so I just want to confirm that that is better than connecting directly from the mixer to the PC. Yes, yes. Okay please, what's the name of the device again please? Audio interface. Just if you Google audio interface you'll get a lot of options. A popular option is the Scarlett 2 input interface. Okay, so this is what an interface looks like especially using for the online one, right? So for the most part in last semester for all our Supernatural Hour Supernatural Hour just to have a clear sound so I had to have wait let me see if I can bring this mic also. So you see this mic over here this is this is not a it's like a condenser but a less powerful condenser mic so this mic and my keyboard would be connected to this and from here it will go to my laptop. So at the moment we are still not talking about the online thing so we'll get to that in just a second alright. Okay, so thank you. You're welcome. Christopher, sorry you have a question. The person who's looking after this whose hand in the mixer would obviously be on headphones and listen to the music coming in and that would be one indication of how the sound is coming across and that would then trigger whether that person needs to start playing around with the knobs but I also wanted to understand in this age of computerization one can it be done automatically you know the computer is automatically going and doing tweaking the treble and the mid and the bass and also is there any indication on this mixer which tells you at what level it's coming what level is the treble are there some lights that are shown or whatever I just wanted to understand that besides just hearing the sound is there any visual kind of representation of how the sound is coming across So I'll just respond and then let Rohit add to it anything. So basically in the basic mixer mixing console that you see in the images these are what are known as analog mixers so there are two kinds of mixers one is the analog mixer and digital mixer right so you guys need to know these things and these will not have any kind of a signal I mean that says okay this is what it is at it's just you controlling how much you want increase or decrease and also the person who's controlling this will not always be on the headphones because if you're actually if I'm controlling this mixer for our church if you've seen an APC he'll be standing in the middle of the congregation and so he's his input is also the main speakers like how is it sounding in the entire room what kind of sound is coming off the speakers and the person who's actually mixing this for online streaming he sometimes will be listening for references on the headphones but then Rohit is there a device that automatically increases and decreases the travel stuff okay so the call that we are on right now is the best example of automated mixing yeah so Google Meet has an algorithm that does a little bit of volume control it doesn't allow things to distort it doesn't allow your voice to break you know things like that it has some AI doing that but audio mixers don't do that the best case scenario I mean as far as automation has come let's say you have 20 microphones and it's a play so you can put it all through this one software processor and it controls levels so you don't have to do the on off and push levels so but that's the best case scenario so far yeah multiple mics you do the tweaking but the volume levels and making sure they're audible it does by itself and as well as visual representation I don't know if you guys can see this but let's see if you can see this so that's like a real time it's called an RTA analyzer yeah so on digital mixers you have that across basically let's dump this one so you have your treble and your bass and the in-betweens are the mids so you have like a waveform showing you spikes so to address the question let's say if there's too much of treble you'll see more spikes in that region yeah so that's that's a visual representation of what could be wrong or what you could tweak what is more what you don't want you can visually look at it and cut it then this is something that's available only on a digital console yeah okay so that's that can be visibly seen only on a digital mixer right? it has like an easy screen yeah so I think Christopher so the digital mixer, from what I've seen is just like a line like a spectrum and if there's a frequency going way above you know that you know that it should not be at that certain frequency and so you'll bring that frequency down closer to that line or below the line and if you know if talking about the bass or the low frequency it will usually be below that line right Rohit? and you could not necessarily go so that's a visual signal so just on the volume one so for example on a guitar you have another guitarist will be able to manage the sound on that but rather bring it up and down so how does that kind of sync with the mixer in the sense will it sort of balance each other? yeah so a bass line would be so even a guitar like you said would have bass, treble and mid so your starting point would be keep everything straight so the 12 o'clock position is basically no changes so you ask the guitarist to keep it at that position, keep your volume at maybe 12 or 2 o'clock and you start tweaking if for some reason the instrument still doesn't sound good then it's a combination of what he can help you out with and what you can do so sometimes it helps if you make some changes as you get to know your instrument you know that this knob helps you get a little better this knob makes it sound fuller this knob makes it sound brighter so as you get an idea of your instrument you know if you cut this the sound guy is going to get a better quality signal from you so it's a trade off yeah who in a sense just an academic question who's in control when it's in a kind of real professional kind of environment the guitarist wants to basically lower the volume to a very very low level and the mixer guy is now sensing there's maybe too low for the audience but the guitarist is he has purposely kept it at that level so that you know it will slowly build up so I guess it should be the guitarist right who's controlling it not really so that's a battle that's been going on for decades but I was going to say that but ideally you would want to get an understanding so here's one more thing it's important to get build relationship with the worship team so they understand what you're trying to get at yeah so if it's only their agenda or only your agenda then confusing questions like this will have to be addressed and often go and address and you don't exactly know what happened that day so it's a mix but primarily it's the audio guy who takes the call of what's heard outside yeah as far as what he can hear like we have monitor speakers for them to hear themselves now that he can be the judge of how much he wants but as far as what the audience hears whoever's at the mixing desk takes the call thank you yeah thanks Rohit I think you mentioned a very important point that the relationship build a grapple between the musicians and the sound person so I think I've seen a lot of friction in the past between these two isn't it so one the musicians complaining about the person at the sound mixing console and the person at the mixing console saying hey you're not singing loud enough I can't give you more than this because you're not singing into the mic extra stuff like that right so there's always been this battle for the decades but yeah next up a mixing console guys and Louis see your question is it general principle for sound engineers to drive their sound so loud in small spaces or is it just bad mixing it's just bad mixing I guess it's yeah cool so let's move on so this is what the back side of a mixing console looks like right so this is the mixing console you see a lot of channels where the cables will be plugged in for input right all you see one of the important things here is the input that means for example a mic one say pastors mic will go into one of these channels that's the input right and where's the output here it's a yeah there's a major output group output stereo output so output is where another cable goes from this section into the speakers so everything is connected over here so this is the real deal guys mixing console if you don't have a mixing console and have all the microphones and instruments really no use so in addition there are some more gadgets or gear to make your sound a little bit once again this is what is known as the equalizer that once you have a mixer and again if you have the budget to add to your gear what an equalizer does is it refines the sound like it's that's basically what it is isn't that what it does it's refining tweaking and making it more crystal clear kind of thing isn't it you get more detailed about the frequencies than it was isn't it depending on the source you tweak so that the tone sounds natural, fuller clarity okay right that's an equalizer so guys just a couple of minutes ago we spoke about the frequencies and also the visual thing and I mentioned a line that goes so do you mind just very in simple words just explaining what the 32 is and all the 16K is so which is the high frequency and the low frequency I mean yeah so sound that you can hear is from 20 hertz to 20 kilohertz so that's basically what they've given here and to simplify to a mixer with just three knobs the comparison would be let's say the knob that says 32 64 125 would be the lows 250 to 2K would be the mids and 4K to 16K would be the highs so yeah okay so 32 hertz 64 hertz and 125 hertz are your base frequencies basically isn't it so dB stands for decibels guys I'm sure you have heard somewhere in the science class frequencies and waves so you push it up and down it increases or decreases that particular frequency between 250 and 2K is your mid frequencies and then from the 4K to 16K is your high frequencies that's the treble and so the sound person the technician will understand all of this how to control which works best for a certain hall or certain room and cut out those frequencies so that's what an equalizer is all about and and I think another important gear is the amplifier basically now what an amplifier does is in simple terms it just amplifies you know the sound in this context because we're talking in terms of the sound it takes say a weak signal a wave thing and then it just makes it big but so this is important isn't it I mean if you have an amplifier before it goes into the mixer isn't that right you need an amplifier before it goes to the speaker it's between mixer to speaker has to go through an amplifier so yeah either the amplifier is a separate unit or it's built into the speaker so those are the two kinds of speakers you'll come up with and they're called active and passive speakers has the amplifier baked into the speaker itself and a passive speaker has the amplifier as a separate unit and the speaker is a separate unit and it amplifies the sound into the speaker so again so just like there are two kinds of mics one is the dynamic mic and the condenser mic there are two kinds of speakers basically I mean for us to understand so that is the active speakers and passive speakers isn't that right Rohan and so it's the active speakers that has an amplifier in built yes in built in the speaker the speaker in the amplifier is one module yeah so you don't need to invest yeah it's just one module yeah okay and if you're having passive speakers I'm assuming the passive speakers are more budget friendly yeah so one amplifier and you can with one amplifier let's say initially you buy just two speakers you can use the same amplifier and buy two more and it would take care of that as well two more speakers you mean yeah two more speakers just two more speakers alone so since the two modules are separate now let's say be a third of the price cheaper or something like that right okay so let's just pause here as in do a quick recap of what we've just spoken about so one is all of us need to know what a microphone is like we all know what a microphone is and what it does and then we just spoke about the mixing console and then the amplifier I think is is it in your opinion do you think these three are like the main gadgets important gadgets you know like the building blocks or the fundamental things that we need to invest in first like speakers amplifiers and mixing console speakers amplifier mixer microphone yeah that's it you can call it four things yeah okay all right okay so I mean if you just start talking about this this topic I don't want to continue and know that we have only four minutes to the break I think we'll just kind of take a pause here and then we'll take a quick ten minutes break and we'll resume is that okay is this helping you all first of all everybody the non-tech guys is it helpful good to know information what do you all think okay all right all right hey you're a techie isn't it you can also add your inputs bro I didn't see you so awesome anyways we'll take a quick we'll take a ten minute break and resume from where we left off right thanks


What's going on everyone? Sam here with late in sports cards, and I am ripping one box of 2022 Penini Don Russ baseball for Jeffrey S. So good luck Jeffrey. Let's pull a wander out of this. That'd be cool Wander gold auto. That's what I'm feeling. Feeling a wander gold auto That base will not ship out of this Jeffrey you will get all of your inserts hits Anything numbered and any I'll pull wanders out for you as well There you go. Here we go. Good luck here Jeffrey. Got Lindor Jake Cronenworth to 2022 and Babe Ruth on the blue. Glad he's senior Nice bomb squad. Shohei Otani to 999. Nice Otani Got blue Zek gallon as well. What's up, Kenzie? I'll just handed the numbers And the autos obviously. Diamond Kings to 2022. That is Casey Mice and Akunia blue I've you know, I've gotten it before dude. That is tough. It's crazy. That one is really tough Nice bomb squad this time Mike trout to 349. There you go. Jeffrey nice hit there on the Trouty and Josh Chisholm blue Marlins kind of a color match We're getting technical and in the house here Nelson Cruz to 2022 red and Cody Bellinger blue.  There's gonna be a you see kukuchi On the Jersey card to 99 nice player Warren on the yuki or you see I should say nice one there 99 and Brian Reynolds blue Patrick wisdom Austin Riley blue Jared Colnick the list Garcia got independence day Patrick wisdom and Blue rookie Jake Burger Ozzy Alves Brendan Woodruff to 2022 Brewers and blue Ryan mouth Castle Orioles Looking for our two autos some more color hopefully as well. Oh, we got a redemption.  That's what we're looking for Let's go on the wander.  Oh, yeah So nice you got to say it twice Nice wander Congrats, man.  Let's go on the wander Heck yeah We hit wonders That's what we do. We hit wonders. Do you see O'Neill cruise on the Liberty parallel one of these per box nice Let's go you're killing it right now Jeffrey How about a gold bomb squad Shohei Otani the 99 behind that? What a box, man Jacob Stallings as well. Nice. Let's go That O'Neill cruise is sick. You get one of those per box and the checklist is huge There for a second Diamond Kings to 349 is John Carlos Stanton 347 excuse me John Carlos Stanton and Pete Alonso color match on the blue It was a series Cedric Mullins to 2022 Orioles Juan Soto also to 2022 Interesting two reds in that one and Matt Olsen on the blue. It's up ironic Carlos Rodan We've got Jay Ram Jose Ramirez to 103 103 RBI is in 2021 Not good. No worries Ozzie Smith on the blue We've got Chris and then you so not the next break drew the break after that's when you'll be gone So pretty close Yeah, man. It's been fun. It's been a great box Kyle Muller on the blue Yeah, you could know never have a Never be shy to ask when you where you are in the queue drew. No never an issue, man Got wow, let's go marbles. Wonder franco to 999. Holy cow, Jeffrey Absolutely destroying this box Blue al-tube behind that one Let's go man. Holy cow. What a box Zimmerman got Jose Ciri rookie to 2022 And Aaron Nola blue behind that Got Seth Romero on the What is that silver autograph? Nice one there not numbered on the flea retro And josh hater What's going on Nick?  Get that right out to you