ITEMS FOR SALE --------------------------------------- gallery

Tuesday, June 23, 2015


Well! it has been a long time since my last post. it has been a pretty busy past few months. Heidi an d i bought an old fixer house in southeast Portland in late February, and there has been little time for new projects that are not related to fixing up an old-dump house. but inevitably we got in and set up, and i have been spending most of the last month and a half building a custom synth for none other than Meng Qi! he contacted me shortly after my last post, and asked to have a custom synth made. he was willing to wait until i was moved and set up in my new shop too. how could i resist?

After some back and forth, we came up with a general formula for the synth-to-be. it would be comprised of two sequencers with capacitive-touch sensors, two voices with analog filters, frequency modulation, reverb, a few modular inputs and outputs, and a Meng Qi logo. knowing that this would likely turn in to a pretty large and time consuming project, i quickly got to work designing synth. the project did end up taking almost two months to design and build, but actually, it could have taken much longer and i am actually kind of impressed with how quickly this one came together, considering the complexity of the build.

(before jacks were added)
The first thing i drew up was an overall signal path schematic to work from. from there i prototyped each part of the synth in small sections. and by small, i mean four breadboards stuffed with circuits. prototyping is always a little difficult on this scale, because it is not really possible for me to build the entire synth with all of its hardware on breadboards. i suppose i could try, but i have found that a circuit on a breadboard will likely always need some amount of debugging once converted to a circuit board. my resolve is to design everything into working sections, connect them to their respective hardware, connect them to each other, then cross my fingers and turn the power on. crossing my fingers has never helped though. certainly not in this instance. however, when all of the shorts and reversed connections were solved, the sections of this synth all played pretty well together. i didn't have to swap out too many components, which was nice for a change. 
One thing that did kind of give me trouble though, were the capacitive sensor switches. i bought several of these capacitive modules on ebay from china. the TTP224 was something that i had always wanted to play around with, and this was the perfect chance. the modules are very cheap, and have lots of modes to choose from. i tested the modules when i got them just to see how they worked, but i actually didn't test them with the circuit until everything was wired up, so i really had no idea if they would work, and my whole interface was kind of designed around them, so i crossed my fingers extra hard this time. thankfully they worked just fine, but i did have to change the design a bit once i was able to actually see how the sensors would play with the rest of the device. initially, i had thought it would be cool to have the ability to change the input mode of the sensors from SINGLE to TOGGLE, but in order to do that, the power to each module has to be turned off before the mode can be changed. that reset period has to be held for a good second too, to get the module to fully power down, so the mode switch was a three position switch where the center position was reset. the whole idea was kind of goofy though, and when i was able to use the sensors with the rest of the circuit, i found that the TOGGLE mode was probably redundant, as well as confusing, because all or any of the sensors can be toggled individually, and since the inputs were being sent out to a priority encoder, it just seemed over complicated just to hold a specific step. the setting also conflicted with one of the envelope generators' mode, so i decided to get rid of the TOGGLE mode, and its goofy switch, and add some other cool stuff like an extra envelope generator mode, and glide for the two voices.  
The design of the enclosure is an original design i made in sketch up. i thought it would be cool to try and incorporate some bent panels, just to give it an edge over traditional acrylic face plates. the rounded edges add a lot more character, i think. i had originally planned to paint the face plates a light beige color, but i really wanted to do a blond birch finish on the end cheeks, and i thought the beige and blond would be too conflicting, so we went with blue on a sky-blue tolex. the box assembly went together pretty quick with no problems. i have had my laser cutter for just about three years now, and i am still able to cut plywood and acrylic with little effort. that is unprecedented for a laser tube that is only supposed to last one year! i can definitely recommend buying one from
Once the enclosure was built, i quickly got to work designing the faceplate layout. once the orientation was generally acceptable, i cut some proto-face plates to mount the hardware in, and attach the circuitry. i usually use cardboard from cereal boxes for this stage, because they are disposable and flexible if i need them to be, but this time i used clear acrylic. the rigid plastic did make it a little more difficult to get at parts of the circuit than when using cardboard, but the clear plastic let in a lot more light, which was really helpful when trying to solder deep inside the box.
The circuit boards were mostly pretty easy to design, and i didn't make that many mistakes this time around. i ended up with four large boards for the voices, sequencers, and filters, and one small board for the power supply and loudspeaker amplifier. the sequencer boards were pretty easy to design , just because there were far fewer components involved, but they ended up having more flaws than the other circuits. i spent a significantly longer amount of time designing the voicing circuits, paying extra attention to not make any mistakes that would potentially be hard to find. they ended up working without too much trouble. actually, the biggest trouble maker throughout the whole project was probably with the hardware. i buy nearly all of my parts from China because the low prices are what really make it possible for me to do these projects for so cheap. the downside to that is sometimes you get some dud-parts. i never had this issue as much as i had with this project, so when something wasn't working, it was always the last thing i checked. i found three or four different dud-potentiometers total in this project. you get what you pay for i guess.
Once all of the circuit were mounted in place, and wired up to the hardware, i had to spend quite a few days tracking down all of the mistakes and fixing them one at a time. it is always pretty discouraging when you turn the power on and nothing happens. but you just start going through the circuit, bit by bit, until everything is exactly how it is supposed to be. when the whole thing was finally working, the next step was the delicate task of removing all of the wired up hardware from the proto-face plates, and carefully mounting them to the blue finished face plates. this is always kind of tricky because it is very easy to damage or scratch the paint on the reverse side of the face plate. i use water-based acrylic paint to coat the face plates, because enamels will cause the plastic to form stress fractures. the acrylic paint works great as long as it is not disturbed. for additional protection, i also laser cut dust-guard fabric to place between the faceplate and the hardware. it protects the paint very well, but getting all of the hardware through the dust-guard, and then through the face plates without scratching anything or breaking any wires is kind of a balancing act. it all worked out in the end, but the final week of this project was pretty damn stressful. 
The signal path of this synth is pretty straight forward, but extremely fun to play. basically the circuit starts out with two square wave voltage-controlled oscillators. the oscillators have a pretty wide range, from high to low. I probably should have measured.. the oscillators' pitch is controlled by its own respective 8-step sequencer. each step can be manually tuned with a pretty decent amount of stability, considering the range. the sequencers are driven by a single clock signal, or they can be triggered individually by an external gate input via the respective input jack. each clock input signal, whether internal or external, is sent through a frequency multiplier, and then a divider, before being sent to the sequencer clock input. the multiplier has four settings; X1, X3, X4, and X5. the frequency multiplication is achieved through the use of a CD4046 phase-locked-loop circuit. at lower frequencies, the PLL takes longer to latch on to the multiple, but eventually it ramps up or down until it is in sync. it is actually kind of a neat affect because the sequencer will sound kind of glitch for a while, and then gradually falls into sync, and then totally syncs up. this made it tricky for the external input though, because the PLL is looking for regular intervals, so if you were manually triggering the sequencer or you had a pattern sequencer running to the input, the multiple would be all kinds of crazy.. to remedy this, I simply set up the X1 mode to bypass the PLL to the sequencer, so it is still possible to get the crazy multiples when using the external input, but it can also be controllable in the X1 position. after the multiplier stage, the clock signal is then sent to the divider stage which also has four settings; 1/1, 1/2, 1/4, and 1/8. the multiplier and divider section can create some pretty interesting time signatures, and each sequencer has their own! the two clock signals also have individual outputs too, so it is possible to sync to the multiplied and divided clock, whether internal or external. the sequencer can run in either direction, and the step function can be turned on or off. each sequencer also has eight capacitive touch sensor inputs. whether the step function to a sequencer is on or off, the capacitive touch sensors will interrupt the sequence and hold the corresponding step in the sequence until the sensor is no longer being held, or until a higher priority sensor is touched. the sensors are prioritized from 1 to 8. when the step function to the sequencer is disengaged, and there is no activity on the sensor buttons, the sequence will hold step-8. step-1 is the highest priority step in the sequence, so holding it will overcome all other sensors. if you were to hold step-5, and let go of step-1, the sequence would return to step-5, and so too, if you let go of step-5, the sequence would return to step-8, or whatever lower priority step was held. sequencer A's output goes directly to VCO-A, and also has an output jack, so it can control other CV inputs, locally or externally. sequencer B's output can be sent to six different parameters of the synth; VCO-B, internal clock VCO, VCA-B, VCF-B, VCA-A, or VCF-A. if sequencer B is set to anything other than VCO-B, sequencer A is sent to VCO-B, and the two VCO's are loosely synced. each VCO has its own TUNE/GLIDE switch and knob. the switch sets the function of the knob to either TUNE or GLIDE. in TUNE  mode, the knob will detune the respective oscillator by about an octave, give or take. in Glide mode, the knob controls how fast or slow the oscillator transitions from step to step in the sequence. the range is pretty substantial. I am really glad I included this. the two voice VCO's are sent through their own signal chain. first, they are split in to two identical voices, 1 and 2. each voice is then sent through a frequency divider with four modes; 1/1, 1/2, 1/4, and 1/8. each divided frequency is then sent to a pulse width modulation circuit. each of the four PWM circuits can be controlled manually, or control can be bypassed externally with the corresponding CV input jack. the manual control knob acts as a threshold control to the parameter when it is being controlled externally. each of the four voices are then sent to their own respective volume control knob. voices A1, and B1 are also sent to their own XOR ring modulator circuit. the XOR is not like your traditional ring modulator, but it really works well. an XOR gate is one that has two inputs and one output. if the inputs of the XOR are the same, the output will be low. if the inputs are opposite each other, the output will be high. put audio frequencies on the inputs, and you have FM! A-1 and B-1 are sent to one input of the respective XOR gate, and the corresponding second input is set by a three position switch. A-1 can be modulated by A-2, B-1, or B-2, and B-1, can be modulated by B-2, A-1 or A-2. each XOR voice has its own volume control that mixes the signal with the VCO's other two voices before being sent to its respective filter and amplifier circuit. both voice A and B have their own voltage controlled filter and voltage controlled amplifier. the VCF is a 24db/oct. band pass filter with resonance control. the cutoff frequency of the filter can be controlled manually, or eternally using the corresponding VCF bypass input jack. the manual control knob acts as a threshold for the external input while in use. the VCA can be controlled in the same way, with its respective VCA input bypass jack. after each voice has been sent through its respective VCF and VCA, the signals are combined and sent to the effects processor. the effects processor is based around the COOLAUDIO V1000 chip. it is a 24bit effects processor with 16 built in programs. it includes reverbs, delays, flanger, and more.. the real fun starts with the bit-rate knob though. rather than using a fixed frequency crystal to clock the V1000, I used a voltage controlled oscillator. this effectively pitches the processor up or down, and it sounds really cool, especially when sequenced, which can be achieved with the external bypass CV input jack. the manual control knob acts as a threshold control when the bit-rate is being controlled externally. the effects section also has a WET/DRY control knob to control how much of the original signal and the effect signal is fed to the output. from there, the signal is sent to the master volume knob, where it is connected directly to the line out jack. if there is nothing plugged in to the line out jack, the signal is sent to the built in power amp and speaker.
hmm, what else? oh yeah, the envelope generators! each voice(A and B) have their own envelope generator too. the envelope generators have three modes each; SINGLE, GATED, or CLOCK1(2). in SINGLE mode, the envelope will only trigger when a capacitive sensor is first touched, and will not retrigger until all of the voice's capacitive sensors have been released, and one is touched again. in GATED mode, the envelope will only trigger when a capacitive sensor is held, but it will continuously be retriggered by the respective clock input as long as a sensor is held, regardless of whether the corresponding sequencers' step mode is on or off. in CLOCK1(2) mode, the envelope generator will retrigger continuously to its respective clock input, regardless of the sequencer mode. each envelope generator's input clock can also be bypassed with an external gate source with the corresponding external bypass input jack. the envelope generators have manual controls for ATTACK(rise time), DECAY(fall time), and DEPTH. each envelope can be sent to one of four of its respective parameters; VCA, VCF, PWM-1, and PWM-2. the envelope generators also have their own secondary output jacks to connect to other CV inputs, both externally or locally. however, the envelope outputs can not be controlled be their corresponding DEPTH knob. the out put is always set to full. all of the 12 input and output jacks on the rear panel were actually not in the original plan. I added them last minute because I felt it would be criminal to leave them out :)
well I guess that about covers it. needless to say there was really no doing this thing justice as far as a video clip was concerned. with the additional input/output jacks, the sonic possibilities of this machine are vast. I made a video anyway. I shot it before the additional jacks though.
I am really going to miss this one. I keep looking over my shoulder, thinking it's going to be there, but it is off to its new owner now. good luck, my little blue friend!! 

(before additional jacks)

Wednesday, February 11, 2015


This little project came to me while i was cleaning out the basement. Heidi and i are moving soon, and i have been trying to liquidate as much as i can before we go. we have lived in this apartment for 10 years now, so our basement was full of years of postponed projects and toys that i have collected. i have actually done pretty well at cutting my collection down to bare necessities. i did however end up filling one box with things that i thought i should maybe sleep on before deciding to get rid of them. in the box was a fisher price guitar from the late 80's. it had been so long ago that i had added it to my collection, that i wasn't even sure if i could remember what it sounded like. i do remember having the keyboard version that was sold around the same time. i remember that keyboard having particularly terrible sound. for whatever reason, i ended up scrapping the keyboard, but kept the mainboard over all those years. i'm not sure why, but now i'm glad i did. when it was finally time to make a decision on whether or not to keep the guitar though, it occurred to me to maybe plug it in and have a listen first. i did, and the sound was terrible! so terrible in fact that i decided to open it up and see why. well, one thing led to another, and i decided that i probably had enough time before we move for one last project. 

Upon opening the guitar, i quickly found that the primary reason the sound quality was so bad was because of the way the voice was generated. the guitar's voice chip sent 8 digital parallel outputs to a shift-register/ resistor array, in some sort of external DAC(digital-to-analog converter) configuration. the digital outputs were also being sent to the keyer/programmer chip before being sent to the shift registers to be mixed. kind of seemed weird to me, but i guess it kind of made enough sense to move on. i tried to find some kind of envelope control for the guitar voice, but it seems that that was being generated digitally too. so that's why it sounds so terrible! well, there would be no 'cleaning-up' the sound here. instead i focused on that DAC business. mixing in the raw digital signals to the audio path made for some great distortion. i also thought it might be cool to send the digital signal through a PWM(pulse-width-modulator) circuit, as kind of a highpass filter. the PWM sounded great, but none of the combinations of the digital outputs and the analog output sounded very good together, so instead of making a mixer section for the 9 different output options, i just picked out the 6 most harmonic sounding digital signals and put them on a six-position selector switch. each of the six 'timbres' have unique harmonics. especially through the PWM circuit. on one end of the spectrum, the voice is loud and has rich harmonics that carry. on the other end of the spectrum the voice is total 'dial-up' noise. then there are four varying levels in between. 

The guitar originally had three strummer paddle switches. to play the guitar, you would hold a note or chord on the fretboard, and strum the paddle switches like strings. when playing a single note, the three paddles all strum that same note. when playing a chord, the paddle switches play one note in the chord individually. i wanted to replace the strummer paddles with an LFO(low-frequency-oscillator), but i also wanted to maintain the chord strumming option, so i built a 3-step looper with a CD4017 chip to cycle through the notes sequentially. i added individual switches to the outputs of the CD4017, so that any or all triggers from the looper to the strummers could be turned on or off in any combination. i also added a big arcade switch to act as a manual trigger for the first string, or the root note of the chord. i may end up going back in and changing the manual trigger to the second string though. i later found out that string two is responsible for advancing the melody recorder in playback mode. more on that later.

at this point the guitar was sounding really a noise-loving kind of way. the sound still needed something though. i didn't want to go too crazy on this project since there wasn't much time, so i decided to add a PT2399 echo circuit to the mix. it did a great job at taming those harsh digital timbres. after being totally satisfied with the sounds i was getting from the circuits i had built, for some reason i really wanted to hear those digital noises through a lowpass filter. i ended up stripping out three buffer/filter stages from the original signal path, since i wouldn't be needing them, but there was one of the four op-amps of an LM324 that was still needed for the weird power switch circuit in the guitar. this meant that i had 3 left over op-amps to use, so i went with a simple 2-pole vactrol based lowpass filter. this is where things got stupid... while i was reverse engineering the mainboard of the guitar, i was constantly flipping the PCB(printed circuit board) around to see the tracings on the bottom, and the components on the top to draw out the circuit to better understand it. i did a great job of drawing everything out, but for some reason i reversed the power pins to the LM324 in my drawing... you would think that after all of these years of using LM324's, i would know by now which pin is positive, and which one is negative. thanks dyslexia! anyway, i built up the filter exactly how i had drawn it into my guitar schematic. it wouldn't work??? no, why would it? i tried a million things to try and figure out why every time i turned the power on to the filter, my voltage would drop. i tried different filters, different power supplies, different voltages... at one point i thought that the regulator to the guitar circuit just wasn't capable of sending any extra current to the filter, so i decided to give the filter 12 volts to see what it would do. as i was pulling a jumper carrying 12 volts over to my breadboard, the  jumper sprung out of my hand and landed directly on one of the pins to the guitar's voice chip. from then on it didn't make a sound. all of the other pins were still fine. they all did what they were supposed to, but this pin gave me nothing. it was the pin that sent the 'enable' signal to the DAC's shift register, so no sound would come out without it. DAMN! this is when i remembered that i had kept the mainboard to the keyboard version. i dug around and found it, and thankfully the voice chip was a match. i de-soldered the old one and soldered in the new one and it worked again. it was then that it occurred to me to check the polarity of the op-amp. it was backwards. i swapped the polarity and the filter worked perfectly.

Once the circuit was finally working, i quickly drew up some faceplates for the guitar, and started tooling the enclosure to make room for all the new hardware. after that, the enclosure would need a substantial cleaning. with the exception of some coloring-crayon stains here and there, it came out pretty clean. i then drew up a little circuit board design for all of the additional circuitry, and engraved it with my CNC. i did have a little bit of trouble with the PCB though. i forgot a few components in my 'bill of materials'. when i used all of the components that i had listed, i just assumed it was done... oops, forgot a couple. eventually it all worked out great, and assembly was pretty smooth. after everything was built, and the guitar was all closed up, i started playing with it. not only did everything work exactly how it should, but i also realised that this guitar has a pretty BAD-ASS SEQUENCER! i knew that it had a record and playback function, but i didn't end up trying it out until everything was said and done. the guitar has a 'record' button that puts the guitar in record mode. in record mode, the fretboard is used to record up to 39 notes without the need for the strummer switch. in playback mode, the second string plays the sequence one step at a time on each strum. since i wired up the strummers to an LFO, the rate of the sequence can be played back independent of the guitar's internal clock(pitch). at the end of the recorded sequence, it restarts at the first step and plays through continuously, and there is no noticeable gap between the first and last step! very cool. i am very glad i didn't just give this little guitar back to goodwill. 

This time around, i didn't film a video.. i tried, but i wasn't able to get good footage and play cool stuff at the same time. my camera skills are just too horrible. instead, i just recorded some audio and put it to a slideshow. please let me know if this bothers anyone. just makes more sense to me.

Friday, January 23, 2015


Ahhh... internet at last. been having trouble with my connection for the past week or so. haven't had the opportunity to post. the NT03 is the latest of my NT(noystoise) series. i initially started developing the NT03 in early November of 2014. the first of the six was completed at the beginning of December, but a commission came my way, so i put the rest on hold for a month before finally finishing them all. unfortunately the commission fell through. thankfully it was only one month wasted. hoping to quickly recoup my losses, i cranked out the final five NT03's in record time(two weeks), only to find that my 3 month old CenturyLink DSL router was all dried out. one after another, i finally got a replacement that works(for now). now to catch up!

The NT03 consists of two square wave voltage controlled oscillators, a holtek voice modulator circuit, a voltage controlled filter(VCF), and a low frequency oscillator(LFO) that can either/or modulate the filter cutoff, gate the voice modulator transpose sequencer.

The two VCOs are made up of one 74LS124 dual VCO chip. i was able to get a pretty good deal on these chips some years ago, but i haven't really put them to much use. this felt like a good opportunity to use them. i also had a few holtek HT8950 chips that needed to be used. the HT8950 is basically just what you would find in one of those toy megaphones that turns your voice into a robot voice(all circuit benders should know what i'm talking about). the difference in the HT8950 is that in addition to being able to incrementally select the pitch setting of the modulator, there is also a three bit parallel input that can be used to select the chips' eight pitch settings; Robot, x2, x1.6, x1.3, x1, x.9, x.8, x.6. the sample rate(BIT RATE) is resistor set. initially i tried clocking the UP/DOWN inputs on the 8950 with an external oscillator, but found that there is a pretty significant debounce protocol built in. this makes it difficult to achieve faster transitions at lower sample rates, so instead, i built an eight step parallel sequencer from the CD4029 chip. this way the eight pitch modes can be accessed quickly with no debounce(latency/stutter). the sequencer can also advance in either direction.

After the two VCOs are mixed and sent through the voice modulator, they are then sent to a resonant 12db lowpass filter(VCF). the filter's cutoff can be modulated with an envelope derived from the sequencer clock, but the attack and decay of the envelope are preset. the filter cutoff, pitch of VCOs 1&2, and the sequencer clock rate are all controlled by one of four joystick axis. the 3D joysticks are a recurring theme in my NT series. this time i decided to use all white thumbsticks, just because they seem to go with everything. they do tend to get dirty though..


Each of the four joystick parameters can also be controlled externally, although the joystick still controls the maximum threshold of the incoming control voltages(CV). the frequency of the sequencer clock cannot be controlled with a CV, but it can accept incoming clock, or negative going gates. the sequencer clock can be triggered internally and/or externally. to advance the sequence internally, there is an 'ENABLE' switch, and a 'DIRECTION' switch. the DIRECTION switch controls the direction of the sequence with either internal or external clock advance input.

The NT03 also includes BIT-RATE control, resonance control(Q), VCF MOD switch(on/off), POWER switch, VOLUME control, LINE OUT, clock rate LED, and center positive 9VDC supply input jack. the NT03 draws about 60ma max, and can also be powered by internal 9v battery.

The NT03 enclosures are made from laser-cut plywood and laser-cut acrylic faceplates. everything is made inhouse(in my house) from scratch. when i finished the first NT03, i had originally intended on painting them all primary or secondary 'candy' colors. hence the yellow one. after some time away from the project though, i thought it might be nice to come up with some colors of my own. i ended up mixing all of the colors for the final five by eye. some are a clean wash, and some ended up with some inconsistencies. namely the olive green one that has my big fat finger print in it. i suppose i could fix it or change the color, but despite the imperfection, it still looks really clean. if no one buys it, i'll just have to keep this one for myself.