Circuit Bending a Cheap Toy Piano - Part 1 - The Cheapening

hello here i am again and uh welcome to well this little thing i want to take a break from building synthesizers for a little bit and i yeah a nice little walk to the local second-hand store they're open again yeah i saw this thing cost a whole whopping 80 cents i looked at it and i was like you know what why not i'm gonna buy it i've been playing with the idea to buy it buy a cheap ass little toy um keyboard and turn it into a little um synthesizer yeah this thing there's some space here for knobs and who knows what i can do with it but this thing is wow it's all sorts of special so yeah let's turn it on it has well it has this sound which comes from the microphone yes this thing has a microphone believe it or not and it sounds amazing it's just a cheap little dynamic microphone i think or maybe in a cheap little condenser just about see it in there but um yeah this thing picks up a lot of noise uh just keep it next to any uh power cable or whatever and now the sounds on there um are very minimal you have piano organ and melody now piano sounds like this you can immediately hear that it's monophonic if we try to play a chord tends to play the highest note not interestingly and if i hold a note and then play more notes [Music] it doesn't go back to playing that note uh some uh like monophonic toy keyboards do do that if you hold a a note and i play another note we'll play that new note and then go back to the old mode immediately so you can make like these little trill effects and stuff unfortunately this one doesn't do that but if i switch to the organ sounds which is well the exact same sound but with a different envelope so yeah nothing special but interestingly normally when i play a note it immediately fades out however if i hold the notes it's starts holding any note you play so that's actually kind of a cool effect now finally there is melody which so okay beautiful so that just plays a bunch of melodies uh yeah that's basically it that's the entire thing okay so this is the back side uh this is the battery uh folder oops and there went the screws where shall we start shall we start with the cardboard here okay so usually on these cheap ass toy so you usually have a little bit of rubber or foam on the back of the speaker to stop it from vibrating to keep it in place that kind of stuff this speaker however doesn't have any proper damping on the front there's just nothing there it's just on the plastic and on the back side they have a piece of cardboard so yeah i mean it's cheap that's that's something that's certain another interesting piece of construction here is this thing so yeah i normally just have like some screws in here there's one screw here which just it's just normally mountains and then here they decided to just you know just slap a piece of plastic over there a kind of a macgyver way of keeping the pcb in place just a piece of plastic nothing special and just that just pushes the pcb in place and that's it now we're removing the plastic bracket i noticed these two legs here just sticking through the board turns out that this is actually an led here which is the power light and i just didn't bother to snip off the uh the legs they just bend them and put them under the little piece of plastic there but there's more interesting stuff on this thing because this this is the gift that just keeps on giving um let's go over here to this part of the pcb so i was wondering like what is this thing here it kind of looks like there is a button here or something but it's right under the keyboard as you can see like the keyboard is right under there so and i think yeah what could that possibly be well turns out it's the chip i have never seen a chip with a with a cover like this this is just a piece of plastic that they just glued in place and yeah i guess the actual silicone dye is under there for some reason they decided to yeah use this piece of plastic and just you know just push it through the pcb and put some big old glob of glue on there okay so i'll put a bit of a closer inspection um signal goes from the chip through this uh what is this 220k resistor over here and then it gets mixed in with the microphone over here it's passively mixed but there's also the volume slider for the notes that you play which actually don't affect the microphone the microphone just goes directly through this capacitor this pull up resistor here passive mixer to the lm386 the audio from a chip goes through this 220k resistor through the uh um following volume slider which actually just selects a different value resistor here for the passive mixer here and that then also goes through the lm386 to the speaker but that still leaves me with all these extra resistors over here and this capacitor 10 microfarads okay that's a really big value actually that will make a pretty slow clock actually so i don't think this is the clock but what it could be it could be for the envelope because the piano has like this you know the slow decaying envelope could be that they're discharging this capacitor every time you press a key and that would control the envelope i wonder if that's it so that's some possibilities here so okay i need to grab my scope i know sort of where all the signal pads are um so yeah it's time to do something about it i'm also gonna snip off these two uh led leads because they're really adorable okay now i've set it all up i had this big old uh six volt power adapter since this thing runs on four um double a batteries that means that it runs on six volts so that was perfect lucky i had one of those but let's take a look at uh yeah some of the signals because uh i didn't guess some things quite correctly so yeah uh first of all the capacitor over here um i guess that this was for charging and discharging envelopes and that is indeed correct if you take a look at the oscilloscope here i hope that's a little bit visible it should be just about visible if i press a key you'll see that um it basically immediately discharges the capacitor now this is interesting is that they actually um like all the signals are inverted the uh the square wave which is just a single pure square wave coming from the chip that signal is stuck to um i'm gonna get around five volts or something and um whenever you press a key and the note set playing it actually pulls that that line low with a square wave so um and same thing for the capacitor uh currently there's going about 3.8 volts going through this capacitor as soon as you press a key and actually ties that line to ground immediately discharging the capacitor then the capacitor starts charging again and that's the curve you see here it starts charging now for the organ something sort of similar happens but it discharges it through a resistor i'm not sure if that's one of these two resistors here though i do see that they're connected to the same same connection here so perhaps it discharges through one of these resistors [Music] which means you get a slight attack on the envelope and then when you release the key it seems to discharge it with one of these other capacit uh sorry through this one is these other resistors uh fairly immediately well charging the capacitor again so you get a very short release time so yeah i'm gonna guess uh that these three resistors are responsible for for uh charging and discharging uh this capacitor okay so here you can see the signal that the chip produces it's just a single square wave and this is exactly the same for the um for the organ and the piano because they basically sound the same so yeah very basic square wave which means i can do some very very fun things with that so yeah this resistor is responsible for that so this resistor i'll remove so i can inject my own circuity in the signal path and we're gonna have some fun with this add some filters and some effects by the way can i just say look at these soldier joints that is just messy and there's all sorts of crud on there too and what was it somewhere around here and there's like all these little bits and pieces of shoulders like it's splattered all over the place look at this that's this little bits and possible solder whatever soldered this you probably are a chinese sweatshirt worker and i forgive you let's dissolve something hell okay well i've done uh quite a few things already first thing i did is hot snot the bejesus out of this little speaker and um so that's very sturdy in place now so that doesn't rattle around anymore i can finic fox on sugar i also uh desoldered the resistors of the audio output and of the envelopes uh put a little sticker here so i have a reference for later now i often keep the little legs i snip off components because they are great for you know making little jumpers or connections on pcbs or whatever in this case i use them to um make little connection points on the top of the pcb because you know the the solder side is hidden away so i can reach that and i also have to unscrew things and solder things and just put it back in place if you do wires they may not make the right length so instead i did this i just have little soldier points on this side of the pcb now i already made use of them here unsold the microphone because it was very noisy and annoying put two little wires in there and now it decided oh hey let's put a little uh little jack uh take a little jack plug on there so i can you know also put other audio sources through this thing uh another thing i did was add a little power jack for six volts the batteries of course can still just be used but uh alternatively you can also use a six volt power adapter okay well i've wired up the first uh three potentiometers attack decay and release here they are kind of stuffed in there you know i have nice notes so that's the piano so the piano only has the decay control which i can set very short [Music] very long also the organ which uh activates the attack and also sort of the decay and the release [Applause] organ please there we go so that's the organ now we have um let's put this on max so we have the attack set to low [Applause] set to fairly high i do like that they have this this analog envelope generators actually sounds very natural this is better than most toy keyboards um now let me put the attack fast interestingly if you decrease the decay [Applause] [Music] this will also uh decrease the year release time but a little bit differently than when you do it with the actual one it also tends to with the volume so i just leave this one on maximum you can do kind of funky reverse envelope things [Applause] see so if i put the k down kind of messes with the attack and release and volume [Applause] so yeah that's the uh very simple modification so far but i have still have lots of space for more knobs and twiddlies and things time to do a schematic yeah or simulation rather

Channel: R.O.T. Studios

Views: 394

Rating: 5 out of 5

Keywords: toy piano, circuit bend, toy modification, circuit bending, chinese toy keyboard, toy bend, hilariously cheap

Id: cXLADPalYZk

Length: 16min 42sec (1002 seconds)

Published: Wed May 19 2021