Thursday, December 19, 2013


This project has been long overdue. the motivation behind it was to create an easy to use, easy to build, and easy to sell drum-synth. the drum synth would be based around my coveted collection of radioshack "elephant keyboards". over the past several years i have been snatching up these keyboards off ebay when ever i see the chance. i have been known to spend $60+ on them. it's kind of funny too because the people who sell them can't understand why i am offering so much money for a child's toy. the reason is that inside the elephant keyboard is a pretty decent monophonic toy-organ chip, as well as an amazing little two-voice rhythm chip. the toy organ chip is similar to the ek001in that it has an envelope I/O, vibrato I/O, and the two-octave keyboards' switches all share a common bus(ground). it is monophonic though and there is only one timbre: 1/1 square wave. one unique aspect of the toy-organ chip is that the clock oscillator only seems to run when a note is pressed. i found this useful for creating a gate output since the oscillator always returns to the high state once the note has completed, whereas the audio output's initial state changes from high to low depending on the frequency of the last note, and the note before that, and so on... generating a trigger was pretty simple since there is an envelope I/O. not as simple as the ek001 but nothing too complicated. the rhythm chip is really what is cool about this toy keyboard. the chip is separate from the toy-organ chip and has its own clock and everything. despite the elephant keyboard only having 4 accessible rhythms, there are actually 4 additional that are not being used. i haven't compared them side by side but the 8 rhythms sound pretty close if not the same as the ek001's. the main difference being that there are only two drum sounds where the ek001 has 4. the rhythm chip has a start/stop, tempo up, and two tempo down inputs. why two?.. the rhythm chip has individual outputs for each drum sound which is pretty sweet! some older models ek001 variants have this but one thing that NO ek001 has is envelope I/O's for individual drum sounds. that's right, there are 2.2uf capacitors to shape the decay of each oscillator. one of the oscillators is a pretty straight forward square wave that generates the kick/tom sound. the other is a pseudo-noise oscillator. through the control of a 1meg resistor, the decay of each voice can be modulated individually. pretty cool.
well, after years of hoarding up all of the elephant keyboards i could find, it was finally time to use them. in the past i used a elephant-keyboard rhythm-chip to drive a little sequencer. it was really great because the sequencer was driven by the drum sounds themselves so changing the envelope of the two sounds would then change the sequence pattern. i definitely wanted to recreate that effect but i also thought it might be kind of cool to use the sequencer to modulate the envelope times of the drum sounds too to create endless pattern variations. not to mention causing the two drum voices to sound like 8 or more different voices. in the end i decided there would be two four-step sequencers running in parallel, driving themselves to one of the preset rhythms. an 8-step sequencer would also be driven by the pattern, and would control the pitch of the toy-organ chip. the toy organ oscillator is clean and holds notes but it doesn't play very well. at lower pitches it even exhibits a little latency/gating. for this reason i decided it didn't need really nice big player keys. instead i just used the ones that came with the keyboard. i figure they will only really be used to select the root note of the sequence. however the keyboard can be used without the sequencer.  
 the main voice coming from the chip is a nice clean square-wave that is ready for shaping. i decided to use this project as an excuse to try out this idea i had been thinking about. in the past i have tried to make single oscillators sound bigger. using frequency dividers helps a little but its not what i'm looking for. no matter how i divided the frequency, the oscillations would always be in sync. i think that what makes analogue oscillators so big sounding is that while their frequency is the the same, the oscillators are out of phase with each other. i know, pretty basic synth stuff here. the point is i wanted to be able to take one oscillator and turn it into two. in my limited experience with synth-repair, i have learned that this is called "chorus". basically you send the oscillator through a delay chip(pt2399 in my case), and the out put is then recombined with the original sound. the phase relationship between the two oscillations will depend on the clock rate of the delay chip. to make it even better, add a subtle amount of low frequency modulation to the clock speed. i have always used pt2399 delay chips as echo processors, but this opens things up quite a bit. i have never really been too satisfied with the pt2399 echo either. it does the job but as a chorus it is more useful i think. 
i prototyped the circuit and was instantly in love. my next idea was to send each of the two voices though its own VCF(if you are still reading, you know what a VCF is). each VCF would have its own envelope generator that could be triggered(and re-triggered) by key-on-messages, or by divisions of the sequencer pattern. once i had tested and confirmed that all of the circuits would work, i began designing the enclosure for the keyboard. the design is not terribly original, but it is good and i know that i can build more of them easily. i used my sketchup demo to draw the box, then coreldraw to turn the drawing into parts that could be fastened together after being cut with the laser-cutter. once the box was glued, puttied, dry, and sanded, i put on red tolex. i only have two colors, red and powder-blue. once the tolex was on, i designed and cut the cheeks. for some reason i didn't think to look at the cheeks on the keyboard in sketchup before i cut out, stained, and varnished them. they look extremely good. definitely the best results i've gotten so far. unfortunately i didn't really like the way they made the rest of the keyboard look. they are just kind of.. big. not so big that they make the keyboard look bad, i kind of just fell like they make the synth look smaller or as small as it actually is. if that makes any sense. the next one will likely be different. or not, i don't know yet.

 next step was the circuit-boards. i have really enjoyed having a CNC-engraver. i really don't think i will ever go back to perf-board, even for the smallest thing. CNCs are just too much fun! i recently had to order a bunch of new engraver tips because the two that i had were totally busted. i decided to go for the finer pitched tips, thinking that if the tip breaks off, the diameter of the broken tip will still be usable. little did i know how much of a problem these new tips would be. after spending days drawing all of my circuits "vero-board" style, it was finally time to engrave my main-board. when it was finished it seemed fine. the etchings were very thin due to the new skinny tips, but the edges were very badly burred. this hadn't happened with the other tips. i used steel-wool, sandpaper, mini-files, and a utility knife to be sure that there were no shorts. everything looked good so i moved on to populating the board. once it was fully populated, i moved on to the circuit boards that would hold all of the hardware. i took extra steps to avoid getting the burred edge on the engraving, but it still need some work in the end. once all of the circuit boards were populated and wired, it was time to flip the switch. actually i think i was so nervous about turning it on that i subconsciously found ways to distract myself from it for a whole day. when i finally did turn it on, there were problems. apparently all that de-burring i was doing was lodging tiny threads of copper into the grooves and creating shorts all over the place. the circuit was turning on though, and it was making some strange sounds. so i was able to start debugging, which in this case was basically going thorough all off the circuit and clearing all of the shorts one by one. by the time i had solved all of the shorts and found/fixed certain mistakes in my circuit design, the pt2399 was not putting out audio and the keyboard would not re-trigger the envelope generators. also, one of the keys just stopped doing anything. no signal on the pin at all. both the pt2399 and the keyboard chip were fried... i don't mind losing a pt2399, but the keyboard chip was a real loss. thankfully the drum chip was fine, so i extracted it and will save it for another day. the keyboard chip is impossible to remove from the keyboard main-board. i am usually really good at extracting parts but this little guy was  impossible. instead i had to replace the entire keyboard main-board with a fresh one.
 once all of the circuit was repaired and in working order, i began designing the face-plates. after a day or two of designing them, it was time to cut them out of acrylic. when i was ready to cut, i realized i  only had one sheet of clear acrylic left... ok, no mistakes! i was calm and calculated while setting up the job, but it didn't matter. one of the belts on my Y axis had gone limp and it caused the laser to mutilate my design... it was all for the better though. it's been too long since i've "got in touch" with my laser. regular tune-ups are critical. the next day i hit up TAP-plastics' scrap table. now i'm set up for at least a year. once the laser was fixed, i cut the face-plates out. they came out almost perfect. the only problem was that the protective sheet on one had peeled back, and the hot fumes created a scar on the face. i tried to buff it out, but that didn't work. then i tried to melt it out with my MAP torch. no luck there either. i only noticed the scar after i had painted the face-plates and removed the protective sheet. it was late at night so i didn't want to cut a replacement. i would have to wait til the next day. since it was already a loss, i wanted to see what would happen if i hit it with some 1500 grit sand paper. it got rid of the scar and made a really interesting texture on the acrylic. i kept going and buzzed the whole panel until the texture was consistent. it was a little too frosty so i hit it again with the MAP-torch. the result was a glowing/transparent/brushed-steel look. i loved it so much i woke up Heidi and made her look at it. she sleepily agreed it looked good so i did the same for the other one.

 so now everything is ready to go. all i need is a good day or two to assemble it all. everything comes together quick and tight and i'm having fun. before i know it i only have one thing left to do; connect the power supply. for this project i am using one of my re-purposed switch mode power supplies that i find at the thrift store all the time. it has a 12volt rail, 5volt rail, and common ground. all i have left to do is connect the 12 to the 12, 5 to the 5, and ground to ground... i triple-check the terminals to be absolutely sure the voltages are going to the right place. then my dyslexia takes over, and for some reason i connect 12 to 5 and 5 to 12. i turn the keyboard on and hear some distorted garbles from the drum chip, then nothing. i turn it off and then back on... still nothing. i turn it off and check the voltages. backwards! i flip them back the way they're supposed to be and hope that nothing too devastating has happened. i turned it back on and found that the pt2399, keyboard chip, and the rhythm chip are all fried. i took the rest of the day off...
 the next day i gutted everything to get at the main-board that held the pt2399. i disconnected the whole elephant keyboard and grabbed another fresh one. to my surprise the whole process was a lot easier than i thought it would be. the overall design of this keyboard is very accessible. once everything was back in place and working, all i had to do was wrap up. i quickly cut two back panels for the power jack, standby-led, and 1/4 inch output jack. i also had an extra buffer in my circuit so i made an extra pattern sync output. it is and active-high 5v logic signal directly from the 1/1 pattern. it's not midi but at least it's something to sync to. 

this keyboard will be for sale for a limited time at my FOR SALE PAGE. i plan to build more in the future but it might be a while before i have time again, so don't wait. check out the video for more info or email your questions directly to me at


Monday, November 11, 2013


As many may already be aware, my baby-bro got married this weekend. the ceremony was exceptionally original and beautiful, and that means a lot coming from me. i have never really been a huge fan of weddings, and yet, i seem to enjoy them a little bit more than i used to... as well as being one of the groomsmen, i was also responsible for building the alter. it was an outdoor wedding in the high-desert at sundown. i was given the task of building thirteen red glowing sign letters that would spell out LOVE GROWS WILD(the overall theme of the wedding). fabricating the sign letters proved to be a long and difficult process, but after about a month of experimenting with different materials and techniques, i was finally able to come up with a design that would be economical yet effective. 
After the signs were approved and built i just kind of figured, cool, that will be my gift to them. i had wanted to also build them a little wedding-music box like i have done in the recent past for other friends who have gotten married, but i had already lost too much time on the sign letters. 
A couple of months went by and the wedding was just a few days away. i had just finished rebuilding my "NOVELTY SYNTH", and i had a little extra time. what the hell, i would build them a WED-BOX. may as well keep this pseudo-tradition alive. i quickly got to work building a circuit. i found a little toy keyboard chip that had 16 diatonic notes. each note would be multiplexed through a CD4067 chip. the 4-bit word that would determine which note will play is generated by four separate light controlled oscillators. a fifth light controlled oscillator would gate the 1-of-16 note input, giving it the ability to re-trigger each note at one frequency. the audio would then be sent to a PT2399 delay chip. the delay rate would also be controlled by a light sensor. once the circuit was mostly-working on the breadboard, i quickly got to work designing the circuit board in two parts. the two circuit boards would be stacked, and the keyboard chip would be soldered to them. once the circuit boards were engraved, populated, and working. i went to work on the box. it is a little bit larger than the ones i have built in the past. this one was 80x80x80mm. i needed the extra room though, and the dimensions are still attractive. i decided that there would be three windows on the box to show the inner workings. once the design was created, i cut out the pieces with my laser-cutter. i was actually pretty surprised that after two years of owning the laser, it can still cut through 1/4" plywood in one pass. i glued up 5 of the six sides and closed up whatever gaps in the edges i could find using a little watered down wood glue and 800 grit sandpaper. i used an airbrush to whitewash the inside surfaces. i thought it might look kind of cool if the circuits were all monochromatic too so i used the airbrush to paint them all red. i used some heavily diluted blue watercolor paint to stain the outside of the box. after giving it one good rustic coat, i found that i could give it some nice water-markings by blotting some fresh paint on the dry areas. once i was satisfied with the stain, i gave the box a few good coats of semi-gloss polyurethane. once the polyurethane was dry enough to handle, i got to work assembling the box with all of its hardware. i finished the box in time to spend a day or so with visiting family before the wedding. the gift was a success. the wedding was great. i was devastatingly hungover the next day. i'm not proud of that though.

congratulations Duncan and Talia Galvin. i cant wait to meet your kids!

Friday, November 1, 2013


I had originally built this little mod around an EK-001 keyboard back in 2009. from what i remember, i didn't really spend too much time developing the mod and in the end there were a lot of things that didn't really make any sense or work how they should. at the time though, it was useful enough as a pretty little noise-maker. unfortunately though, some of the connections to the main chip were connected "unsafely". in the process of stripping the keyboard down and adding new circuits, i got rid of the 5 volt zener diode that protected the chip from over voltage. the entire keyboard only ran on 6 volts tops, but i assume that with the addition of new connections to certain I/O pins with no resistor protection, over time the chip started to die a little. as more time went by, keys would only work intermittently. the interface was pretty ill-conceived so it was easy to forget what anything was supposed to do, especially since the interface had no graphics whatsoever. 

Many people have offered to buy the keyboard from me since i posted it here on my blog. i have always been reluctant though because ever since i "finished" the keyboard, i had always intended to go back and clean it up some day. well, that day finally came last week. upon power-up, many of the keys were just dead. the audio was low and the range of some of the parameters was unintelligible... i had figured that the problem with the keys was cosmetic, so i thought i would spend a day or so cleaning up the circuit and applying some of my new knowledge to some of the keyboards' shortcomings. when i opened it up though, i quickly found that working around hot-glue and unnecessarily long wires, that this circuit might be too much trouble. especially since i didn't ever get around to drawing a schematic for this circuit. i had kind of assumed that i would find this situation. i usually do when i go back into a project after a few years. i didn't hesitate to rip everything out. not just the circuits, but all of the hardware too. it had all been hot-glued in, and though hot-glue can be great for putting this stuff together, it can be a pain in the ass to work around, especially when trying to add new hardware. the only bit of hot-glue i didn't rip out was what was holding the power switch and two potentiometers in the right-hand corner of the interface. they are mounted really well so i was able to use them in a pretty similar way in the end. one pot would be a master volume pot, and the other would be a tuning knob for the master pitch. the power switch would stay a power switch. 
After gutting everything i had to decide how the new circuit would work. i wanted to keep most of the functions the same as had originally been designed, so i based everything off of that. the keyboard chip was totally fried so i had to use a new one. originally the keyboard's two voices were combined and sent to a frequency divider that spit out 4 octaves that were then mixed by a mini-joystick. the combined voice then went to a pretty crappy little VCF that was modulated by an extremely crude AR generator. i think it may have been my first ever attempt at an envelope generator so needless to say, it was not too versatile. also, i hadn't yet figured out how to trigger and envelope generator with the envelope signals coming from the keyboard chip, so it could only be triggered with the LFO. this must have been pre-oscilloscope-noystoise. the new approach would be to use my latest method for generating an AR generator for the EK001. there would be two separate envelopes for each voice. each voice would have its own filter that would be modulated by its respective AR generator. before being sent to their respective LM13700 based filter, each voice would be sent to its own frequency divider. the original keyboard frequency and 3 sub-octaves would then be combined with the voice's designated mini-joystick. the two voices' octave mixers would be independent, but the Attack, Release, Amount, and Cut-off controls for the two filters would be controlled together using some dual-pole potentiometers i found. as for the original eight timbres that the EK001 is capable of, i have learned that there are actually only 4 separate timbres. the other 4 are just gated versions of the original 4, and don't respond well with the new envelope generator, so i won't use them. 
I have always had trouble selecting a method for pitch-bending the EK001. i have tried transistors, vactrols, opto-isolators, jfets, and even voltage control over the internal clock, and nothing has given me decent results. one thing i had never considered though is using a VCO chip. i had a bunch of 74ls124 laying around so i rigged one up and thought, what the hell, why not? i disconnected the timing resistor and connected the VCO output to one of the terminals. no change. i tried the other terminal, BZZZT, it works! i tried some different timing capacitor values for the VCO chip until i found a good range, and now the pitch of the keyboard is voltage controlled. the VCO chip actually has two CV inputs. one is the frequency control and the other is the range. the range CV has less range so it would be used as the pitch-tuning. the frequency control CV would be used as pitch-bend/LFO input. the LFO would have three shapes; saw, reverse-saw, and triangle. 
All that was left then was the drum machine. originally the keyboard was able to access all of the eight preset rhythms, start/stop buttons, and tempo buttons. there was also a custom section that used another 4520 divider chip to be able to trigger the four drum sounds at 5 selectable sub-frequencies of the master clock. each drum sound had its own six position switch to select one of the 5 sub-frequencies or the off position. this was a good way to make beats but it was nearly impossible to sync them with the preset rhythms. also, the rhythms that the divider produced were just too simple. they needed some swing. i decided that in the interest of space, i would do away with all of the original preset rhythms and all of their necessary buttons. instead i would use the divider chip to gate four separate LFOs that would then trigger the drum sounds at their independently set frequencies. the Reset pin on the LM556 LFO would be connected to the six position switch, so in theory, if the LFO frequency was set lower than the reset frequency, the drum sound would only trigger once upon each reset. i bread-boarded one and it seemed to work, so i drew up my schematics, double checked them, and drew up a circuit board for my CNC to cut out. i made one circuit board for the melody section, and another for the rhythm section that also included the VCO. i wanted to keep the VCO as far away as possible from the analogue filters to avoid crosstalk. it helped. once the circuit boards were populated, wired, and working, i designed and cut the new face-plates with my laser-cutter. i also created a nice little regulated/diode-protected AC adapter input. the keyboard was coming together despite some issues i was facing trying to connect the hardware that was mounted to the top shell of the keyboard to the circuit-boards that were mounted to the bottom shell of the keyboard. i like to keep my wires as short as possible, so quick-connects were very helpful here. now if the keyboard shell is taken apart, the two pieces will only spread about an inch before you have to disconnect things. this was great for space but bad for debugging... 
I finished the keyboard and closed it up. i started playing with it and noticed some issues with the envelope generators. they would not re-trigger for some timbres, while others would attack fine, but never release. i opened it up and had a look i must have plugged it into the AC adapter too, because when the keyboard was opened up on my worktable, it didn't have any problems at all. i put it all back together, but at the time i still didn't understand why it was behaving that way. oh well. i played it some more and noticed that the rhythm section was kind of erratic, and the EG's were doing that thing again! eh, i'll fix it tomorrow... the next day i opened it up and quickly found that the reason the EG's were being weird was because the batteries were drained. duh. the drum machine on the other hand was critically flawed. apparently gating the reset pin on an LM555 or 556 will not put a high signal on the output pin upon reset. it makes sense because the state of the output can't change until the timing capacitor is charged or discharged. my timing capacitors are 47uf so they take a little while. it also seems that if the gating frequency is higher then the LFO frequency, i takes the remaining discharge time plus the charging time of the capacitor to reach the initial triggering of the drum sound. well that's nice to know! after about a day of trying to come up with the solution to the problem or just possibly making it kind of work, i came to the conclusion that there was pretty much no way for me to get the results i had originally wanted with the circuits that were already built. instead i went back to the original design where the drums would only be triggered by the sub-frequency of the master clock. however, the sixth position of each switch would route the respective LFO to its drum sound. the reset pins of the LFO's are gated by the 1/4th output of the master clock frequency. this configuration seemed to give the most consistent results. in the end it gives each of the four drum sounds a good "roll" mode. 
All in all it turned out pretty great. the keyboard really growls and has a warm organ quality to it. at times it can be dark sounding but not too serious. i'm sure whoever does end up buying it will really enjoy making beautiful music with it.

Monday, October 14, 2013


Another of what was supposed to be a quick and easy project; the "Funky Glitch Buddy". The name was taken from a song file i created some time ago that has been floating around my hard drive for at least eight years. i had never intended to finish the track, i only kept it around because the name was catchy. now i suppose i can finally delete that file.
this project began a few weeks ago and was supposed to be a quick little project. my primary motivation for this piece was to produce something quick that i could list on my NEW FOR SALE PAGE. i am doing Noystoise full time now and i need to pay the bills.
In the process of building this toy, many setbacks occurred. the biggest one being that i was never really satisfied with what the end product would be. the concept changed back and forth a few times until i had settled on the overall plan. the plan would be to use the three big keys of this little baby's keyboard to control three pattern generators that would then trigger two independent pseudo-noise generators and one simple VCO. the three keys are not actually pressure sensitive. there are Infrared emitter/receiver modules that bounce IR light off the bottom of the keys. the output of each IR module is sent to a lm3914 which acts as a sort of A/D converter. the eight outputs coming from the lm3914 are sent to a 74148 priority encoder chip. the three outputs from the 74148 are then sent to the CD4089 pattern generator chip. the pattern coming from the 4089 chip triggers the respective envelope generator. so basically, depending on how far down you push on the keys, one of eight patterns will be selected. the other eight patterns that are available on the 4089 chip can be accessed by pushing the respective "shift" button. this simply toggles the 4th input on the 4089. the two pseudo-noise generators are built from scratch using 74273 chips as shift registers. these noise generators are pretty effective and sound really good. unfortunately though, they take up a lot of space because you need an XOR chip to make them scratch, an initial-clear circuit to get them started, and oscillators to clock them. not to mention the two VCAs, two envelope generators, and inverting buffers for the envelope generators. in all something like 22 chips went into this project, so it was in my best interest to learn to use my newly acquired CNC to cut out some nice little space saving circuit boards. it took some time to get my head around it but im glad i did. i don't think i'll ever use perf-board again! not for circuits anyway. the one thing that i was the most satisfied with was having a working circuit upon power up. so nice. 
one thing that was sort of unique about this project is that at no time did i ever just sit down and draw out the entire schematic. it was supposed to be such a quick project that i never gave it a second thought. in retrospect though, i should have just taken a half hour to draw everything up. it would have probably saved me a lot of time shuffling through old notes and datasheets. one of the major things that i overlooked was the power supply... throughout the entire build process,  i had only powered any of the circuits with my trusted regulated 5volt ac adapter. i guess i just assumed that this thing would have no problem running off of a 9 volt battery once it was all built... i was wrong.the circuits ended up drawing so much current that i was unable to even build an adequate 5volt regulator for the ac adapter input. they kept overheating... in the end i sacrificed my trusted 5volt adapter, building it into the keyboard. i really would have liked to have this thing run off batteries but the circuit is just too hungry. to make things even more frustrating, the original faceplate that i had cut, painted and installed decided to crack when i put too much pressure on it while pressing on a stubborn knob. i figured that it must have something to do with the thickness of the acrylic so i quickly cut a new faceplate with a thicker piece of acrylic. it came out perfect so i painted it and let it dry for a few hours. i came back to it later and found that there were dozens of little cracks all around the freshly cut edges. upon doing a little research online, i found that it is a common problem when applying solvents to acrylic. it is called "crazing". there are some ways to keep it from happening but my solution is to just not even bother using solvent based paint anymore. instead i used acrylic airbrush paint. i realized that i probably could not match the original grey color of the original faceplate and the smaller undamaged faceplate still on the keyboard. instead i decided to paint the third and final faceplate black. it came out way nicer than i had expected. i added a 1/4 inch output jack and quickly noticed that there was substantial crosstalk from the noise generators' oscillators. i was able tame it a bit by filtering the power amplifier input with a single 100nf capacitor. however now the master volume control acts more like a filter. i like it though. there is still a considerable amount of crosstalk coming from the oscillators. i assume it is because everything is all smashed so close together inside. i came to the conclusion that it probably wasn't worth trying to fix since it is only really noticeable at the highest volume setting, which is quite loud. when i plugged it in to my sound-card to record the demo video, i didn't notice the sound at all. i'm happy about that.but after all, it is a noise-maker.
Here are some gut-shots. i think there were 5 circuit boards in total including the little VCO circuit seen with the big green capacitor. it took me a while to decide what the third pattern generator would trigger. in the interest of time and space, i used the two transistor oscillator from a cheap toy organ that i had lying around. it worked out well because the envelope modulates the pitch and volume of the oscillator simultaneously. i had originally wanted to put a sequencer in but it was not doable. a cheap sample was my next idea but the sound quality was just to hard to work with.
Here is a shot of the IR proximity sensors. they basically work the same as a photocell would except they only respond to IR light. oh yeah, and they are photo-transistors so they don't suffer the capacitive issues that CDS cells usually do. if they do, its not noticeable.
Check out the video too. 

Also, check out my FOR SALE PAGE
this toy and many others are for sale right now!
thank you for your support

Thursday, September 5, 2013


UPDATE 9-30-2014

Well, my Noise Synth has finally found a home. the buyer contacted me to buy the last NT02 from the series. however, the faceplate of the NT02 had suffered from a significant amount of "crazing" caused by the metallic silver paint. the paint must have had some kind of quick-drying solvent in it. it caused thousands of tiny "feathery" cracks around the cut holes in the faceplate. the cracks have no affect on the structural integrity of the acrylic faceplate, so i just went with it and dropped the price of the NT02 by $20. over time though, the imperfection really started to bother me, so i made plans to cut a new faceplate for it since no one had inquired about it yet, but before i could start, someone did contact me for it. i explained the situation and he agreed to pay a little more for a new faceplate, and more still for CV inputs. 

he told me that he would also like to buy the NOISE keyboard from me, so he wanted the two to match. works for me!!! he also wanted to pay a little extra to have me add some stuff to the NOISE synth. i added a Highly Liquid midi input to control the keys, CV inputs for keyboard pitch, noise oscillator pitch, and PWM, gate inputs for keyboard envelope, noise envelope, and middle F key, CV outputs from noise envelope and PWM LFO, and gate outputs from EG1 and EG2. it wasn't too difficult to conceive of the new mods, but upon opening the keyboard, i realized that this was one of my older projects from before when i started using my CNC to make circuit boards. everything was point-to-point on perf-board. everything was pretty clean, just hard to locate certain parts of the circuit without any reference. while i was in there, i decided to add some more circuitry "pro bono". one thing i had always been dissatisfied with in this keyboard was that the pitch range was so low. the radioshack programmable organ chip that i used could not be clocked very much higher than it's intended pitch, so there was not really much to work with. and because the main voice was being divided down to generate its 15 different timbres, some were too low to even distinguish notes. also, the pseudo-noise generator voice can be synced to the keyboard voice, but the pitch range was so low that it was hard to hear the key changes on lower notes. to remedy this, i built a simple frequency multiplier using a CD4046 PLL chip. now the voice coming from the keyboard is multiplied by 4 before being sent to the timbre divider and the noise clock input. the results are great! the timbres and noise generator are much more tonal. FAREWELL NOISE SYNTH!

UPDATE 12-21-2013
I finally got around modifying this keyboard further. as more time had gone by, my dissatisfaction with this keyboard's LFO range grew. i decided to go back in and fix the problem. the joysticks had originally been used as variable resistors to control the frequency of the LFOs, but 10k was not enough after the joysticks were mounted to the front panel. this is because the physical range of the joystick was limited by the joystick hardware. i would estimate that each joystick lost at least 10% of its range from this. to solve the problem i used 6 vactrols, one for each axis, in parallel with 100k resistors to control the rising and falling edges of each LFO. then i wired up the joysticks as voltage dividers to drive the vactrols. they are the cheapo vactrols from electronics-goldmine, so they do have some latency, and some of them were defective, but the result was effective. now the range of the LFOs is ten times greater than they were before, so you can actually distinguish the shape, whereas before, the joystick really just acted like a FAST/FASTER control. while i was in there i thought it might spice things up if i added some soggy delay, so i threw together a pt2399 echo circuit and put it in. it definitely gives the whole keyboard more dimension. before, the sound was dry and a little harsh. now that this keyboard is whole, i feel better about selling it. it is for sale now at my FOR SALE PAGE


This project was based around the lesser known Radioshack Programmable Electronic Organ. they are not exactly the most satisfying of toy keyboards mainly due to the fact that the keyboard is monophonic. it does however have two voices to choose from; piano and organ. the keyboard is also equipped with record and playback modes. in record mode, up to 19 notes of variable lengths can be recorded to the internal sequencer. in playback mode, any of the white keys will reset the sequence from the beginning. if a white key is held down, the sequence will reset once the last note in the sequence has been reached.  the sequence will be saved in playback mode until it is overwritten or the keyboards' power is reset. 
I usually make an effort to snatch up these toy organs when i get the chance as the inner workings offer a lot as far as modification is concerned. there is a rather nice 40-pin organ chip inside that actually offers a lot of potential. one thing that really surprised me though is that there are designated gate and trigger pins on the chip. this makes adding additional circuits such as envelope generators much easier.  one thing i was pretty disappointed with though is the range of pitch modulation this thing can achieve. at stock functionality it is pretty much clocked as high as it can go. not only does that interfere with how well the voice can be divided, but also puts a pretty low limit on how fast a recorded sequence can be played back. oh well, it is just a toy. there may be a way to bypass the internal clock too an inject a faster one somewhere on the chip, but i didn't get that far. it probably wouldn't work anyway.
 After spending a little time reverse engineering the toy and seeing what it was capable of, i started brainstorming some ideas for additional circuits i'd like to add. the monophonic voice was a pretty nice clean square wave so it was not hard at all to send it through a pulse width modulator. after that the signal would be sent to a cd4089 binary rate multiplier. i had used 4089s before as a pattern generator for a drum circuit a long time ago but i had never used them as a frequency divider before. it turned out pretty well and gave me 15 very unique timbres. i had originally planned to have four optional LFO's to modulate each of the binary inputs on the 4089 but upon testing it found that it was too gritty. maybe if the keyboard could operate at higher frequencies... oh well. after the divider stage, the signal is fed to a super basic VCF. i decided early on that i would like to be able to run this synth off of batteries so i took every opportunity in keeping the operating voltage as low as i could. hence the 5 volt VCF. i suppose i could have just used a bigger battery pack but what the hell. after the VCF stage, the signal is fed to an LM386 power amp to drive the internal speaker. the next idea was something that i have been wanting to experiment with for a while now and finally got the chance. i have had this rough schematic for a shift register noise generator circuit that i had been meaning to try out. i prototyped it up on breadboard and it seemed to fit well with the overall chip-tune sound of the keyboard voice, so i built it in. the noise generator can be clocked either by its' own oscillator or by the note of the keyboard's main voice before it hits the divider stage. the pitch of the noise generator will track the keys pretty well, but it would probably sound a lot better if the pitch of the keys were one or two octaves up. again the pitch range... the noise generator is not random. it is just a long sequence that needs a little help getting started. i had to build an initial-clear circuit to set the sequence in motion upon power-up. the sequence can then be interrupted and effectively turned off by pressing the Noise Off button. it can then be turned back on with the Noise On button. the noise generator signal is fed to another super basic VCF, and then mixed with the keyboard voice before being sent to the power amp. the two filters are modulated by two separate envelope generators. each has Attack, Release, and Depth. each envelope generator has a Repeat LFO too. when active, the rate knob sets the frequency of the Repeat LFO. while disengaged, the Rate knob acts as a cut-off level for its' respective VCF. i then thought it might be kind of nice to add some LFO's for modulating the PWM, Pitch, and Noise Pitch. each function has a switch that will change that parameter's depth knob will set the respective LFO's depth. the rate and shape of the LFOs are controlled via joystick. as a consequence of not prototyping my LFOs before building them, the frequency range is limited to the physical turning radius of the joysticks. i really wish that i had seen that coming but its really not that bad. 
the keyboard section's functionality was pretty straight forward. to select the timbre from the CD4089, i used a 4-bit encoder(16 positions).  in the "0" position of the 16, the keyboard makes no sound.  i found that the two voices(piano and organ) would work better more as a note-hold on/off switch. i threw in a 3 position switch for the Play, Record, and Playback functions. i also added a switch that would loop the recorded sequence in playback mode. the toy keyboard that i was working with had sustained some severe damage at some point in its life, and the top 8 keys had to be removed. with the limited pitch range the keyboard was already restricted to, it was a shame that those notes go wasted, so i thought what the hell, i'll add a switch swapping out the lower 8 keys(f3-c4) for the missing 8(f5-c6). it makes things a little confused but the noise generator sounds much better when its tracking the keys.
 It took a couple of days to design the faceplate, but only about an hour to cut it out and paint it. i fit everything in to a beat up wood box that i found at the thrift store. it was pretty beat up when i found it so i had planned to sand and paint it. once i had seen it with all of the hardware in though, i decided it looked better with all of the scratches and chips, so i left it alone. i added a battery compartment to the back, and a pretty sophisticated little ac-adapter switch circuit, as well as a line out(for audio). not too shabby.
 Here is a closer look at the interface
 and a video...

Tuesday, July 9, 2013


this was a quick little project i threw together for some good friends that i had recently visited in Barcelona. i had built something similar for another pair of friends who got married last summer. unfortunately i forgot to take any pictures or video of it before i gave it to them. oh well, they just live down the street. the danana box is basically a heavily modified animal keyboard. actually now that i think of it, it was a guitar... the guitar had 15 notes that were all trigger-able through a common bus(4.5v), so i hooked them all up to a CD4067 analog-multiplexer. the 4 binary inputs are driven by a 74HC193 up/down counter chip which in turn is clocked by a simple 555 oscillator. the four bit word coming from the 74HC193 are fed to the binary inputs of the CD4067 via 4 momentary switches. there is then a momentary switch to change the direction of the up/down counter. if none of the four bit-buttons are depressed, no sound will be made, but any combination of the four switches pressed will produce one of 15 melodies(possibly coprighted by googltubes). the up/down switch changes the direction of the melody. the box has 5 different sounds to chose from. at some point these were sampled animal sounds that had a weird kind of echo to them. this made for a unique set of sounds when overclocked to the point that the animals are indistinguishable. the main voice is then sent to a pt2399 delay chip. on one side of the box is a yellow joystick. on one axis of the joystick, the frequency of the melody can be changed. on the other axis, the delay rate can be modulated. the whole thing runs off batteries and has a built in speaker. one unique aspect of this build is that because space was so limited, i decided to build all of these circuits without PCB. instead, all of the components and chips are all just blobbed together like big circuit boogers. i had never attempted building circuits like this before but hey, it works. i should have taken some pictures...
check out the video n'stuff.