 I'd like to quote him, he says, the gap between mass production gadgets and the ideal of my mind is so big that my inner perfectionist wants me to do it myself. Yeah, so today I'll be sharing a project which actually I made quite a while ago but somehow forgot to share so returning to the debt. And I'd like to start with the motivation behind it, like what can make a product which you probably can buy somewhere from for now while it was there or some limb. And the thing is that given yourself a gap between the moment when you realize you need something and the moment you go shopping is dangerous because in between you can start thinking and you can come up with an ideal picture of a device you need and most likely when you come to the shop nothing will really satisfy you. No mass market product will be good enough and then your inner perfectionist kicks in and just demands that the only way to have a good thing is to make it yourself. So actually the thing I needed was very simple. I just wanted to have some music at my work desk where I mess with all the hardware and everything just as simple as this. But there was a big gap and I started thinking, okay, what do I want? First of all, you know, apartment sizes are shrinking and every little bit of horizontal space on your table is a precious real estate. You don't want to use it for something like a speaker. You want to use it for some stuff you are actively messing with. So hence the requirement has to be small, it has to hang on the wall instead. And actually at this point a sizable proportion of mass market products just goes out. Then the next idea was, okay, how many speakers do I need? There are many options available like 0, 2.1, 5.1, 7.1, whatever. But being a sound engineer in the past as well as another bit of my past, I know perfectly that to enjoy the proper even stereo sound, you need to place two speakers in a proper way, preferably in a proper acoustic environment. You need to position yourself in between in a proper way. Otherwise the waste of everything is just double space, double expenses, double trouble basically. So how many speakers do I need? I need just one. So another big batch of mass production stuff goes out of the window at this point. Then power supply. External power adapter I never really liked them. And power circuits are a precious commodity as well, but there are lots of computer related things on the table. So plenty of USB ports, USB chargers, so you need to be USB powered obviously. Then force requirement coming. I love to have a big sound, by big what I mean. You can have the same volume from a small speaker driven up to 100%, maybe plus 100%, or from a big speaker driven at maybe 5% of its nominal power. The sound will be much better with a big speaker. So that's what I like. I thought, okay, how can I do that? And the last but not least is that I didn't want any volume control on speaker. Because first, there are plenty of volume regulators that are aware. Every media player application has a sound regulator. Then there's overall regulator for computer or for mobile. And then add in yet a third one, a physical one on your speaker. Well, there's just too many. And another thing is that variable resistors, especially the cheap ones, they tend to die really soon in tropical climate. I pretty much wasted quite a few speaker systems here in Singapore before I came up to this idea. So no choice. I have to do it myself. Yeah. So that's the early prototype. As you see, the box is already there and the speaker is already there. So for the speaker, I decided that the best option is basically a speaker for car sound system. Coaxial speaker is reasonably small, reasonably powerful and not really expensive. So for electronics, pretty simple. Based on wonderful low voltage amplifier with balanced output, balanced output means that you don't need this big DC blocking capacitor. Actually, this guy over here is not a DC blocking capacitor. It's an output that is on the power rail, like same as you have in big supercharged cars. That kind of thing. So I really like this amplifier because it works on anything starting from 1.8 to 5.5 if not 6. Unregulated power supply and delivers one watt of output easily and it doesn't need any cooling whatsoever. I mean, I optimized PCB layout a little bit, but there's nothing serious. And a few more little guys here. One is for on and off button and indication because I didn't want a mechanical switch on or off. I wanted push button. Luckily there are plenty of options available and this one is just a little 6 pin IC with a button and two outputs, one direct one inverted and both are powerful enough to just attach LED straight to it. And the third one over protection circuit. I'll get back to it later on the next slide. Why do I need it? For mechanical engineering purposes, I arranged it in two different PCBs. One is electronic itself and another is all the sockets and everything because more often than not you would lack them to be located in slightly different places and also all the sockets that tend to break once in a while so you just throw away one PCB instead of two instead of the whole thing. Now obviously it didn't come without a fair bit of challenges. The first one I encountered since I never designed such things before is that all electronic gadgets these days are just way too smart like a laptop sensing if there is a headphone plugged in if you plug in something but the input impedance of this thing is too high it doesn't recognize it as a headphone so no order signal is going out so we have to simulate it somehow. And another thing is since there are basically two cables one is USB for power and another is a signal cable and you might think that the signal ground and power ground are the same sadly with complicated computer devices this is not the case most of the time so this is just one of the examples of what can happen between signal ground and power ground you don't want to hear any kind of this stuff and another thing you need to remember is that all USB ports they have over current protection that means whenever you have some really loud music chances are it will turn it off so that's why there is this third IC for over current protection and this huge capacitor behind this protection so it accumulates the power basically draws it up to the limit all the time and this did help so that's pretty much all for electronics as no rocket science at all all things were taken pretty much directly from the data sheets for all three ICs nothing really complicated now mechanical engineering this is probably the biggest part of fun the biggest challenge was to find the proper wood material proof to be notoriously difficult luckily I discovered this little shop somewhere at the back of Pyre Libre it has to be it has to have reasonably good acoustic qualities not to seek, not to sin so I managed to find some pine which is not a common material and made a box for the speaker in then little pieces indicator this thing again I had to do it myself because I couldn't find one's big anas in whole Singapore so I had to buy a brass strip and brass rod banded myself through it myself yeah and after a little bit of messing with the wood this is what it was, this is a sample speaker on the wall and another little thing is that where do you put all the sockets if you put it on the underside it's not very good because they can fall out on top not very convenient on the side but on which one how do you know, so I just attached two hangers on top and on the bottom if you want it on the other side just turn this thing upside down easy easy and economical and actually I'm happily using it ever since but still there are two after source like if I will have to do the same thing over again what do I improve first automatic power off if there is no signal for some long period of time the circuit for this it is actually in the data sheet for all the amplifier so it should be released forward and the second thing I would do the top surface slanted the reason is that when it is horizontal it tends to accumulate dust and it tends to accumulate things because everybody tends to put something on top right if it is slanted no way and that by the way is the difference between old double-decker busses and new ones you know the front seat on the second floor the old ones they had a horizontal shelf so people put stuff there sometimes forget the new ones they had it is rounded so no way you can put something there and forget it just gonna fall down straight away I don't know if it was made on purpose or not but it works and now showtime so for its size and power supply it is actually reasonably loud so it was designed for a small room like study room or something and I don't want it to be any louder really pretty happy I think I just gonna pass this around speaker was something like I believe $40 for a pair at Simlim all other electronic components probably were like $10 from RS online as you might have noticed it is mostly SMD other than the big capacitor and obviously ordering PCBs was the most expensive part of it I still have some spares if anybody wants and I will be sharing the schematics and PCB layout and whatever I can share shortly it is my usual problem that I always busy doing stuff never enough time to document it and share and everything but I promise I will do so that's it