Quick Update

so i have been hard at work building yet another beast. its all coming together nicely(so far). been having lots of fun with the pressure sensitive aftertouch hooked up to the pitch and filter cv's. more to come...

UH YEAR

 

wow. this is definitely the longest project i have worked on to date. i began this commission shortly after the "Hartman Mod Job" last february. i was contacted by a guy who was interested in having me build a synthesizer for him that looked like one of Dan McPharlin's miniatures. it sounded like fun and there were some new applications that i was anxious to try out so i agreed. the initial idea was to build a mini synthesizer with a detachable keyboard and as many controls and effects as i could fit. i decided to be courageous and model the toy synth on the notoriously stubborn yamaha pss-30. 

i quickly got to work reverse engineering the main board and taking some dimensions. i made a few rough sketches and headed over to my stepdad's place. he has a wood shop and agreed to help me build the cabinet for the synth. i brought some fancy  hobby wood from home depot that he laughed at. he quickly whipped out a set of cabinets for the synth that i was extremely excited about. i guess i figured that this project was going to be easy... the idea was to build wooden cabinets for the electronics and upholster them in some powder blue tolex i had ordered. i had never applied tolex before but i was confident that i knew what i was doing after reading tutorials and online forums on the subject. however, nothing could prepare me for the giant sticky mess that is tolex. i followed all of the instructions from the tutorial and the directions on the back of the glue and that stuff is wrong! i wont go in to detail on what works because that's what all those other people did, and i thought that their knowledge would work for me but it didn't. basically, if you are going to try tolex, the only thing you need to know is that its going to be a sticky mess the first time, so don't wear your church clothes. it did work eventually though and i got the tolex to stick to the wood. the only problem was that when i trimmed the tolex around the edges, there was a pretty noticeable seam. the was due in part to the fact that the tolex i ordered was powder blue, which is very revealing of imperfections. i guess that's why it was on sale. i figured i would just find something to cover it up since everyone i showed it to seemed to think it was too noticeable too. but i would cross that bridge when i got to it. 

the yamaha pss-30 has quite the reputation for being extremely difficult to modify because it's circuitry is so well consolidated. it is nearly impossible to interrupt any of the keyboards functionality without rendering it useless... this little keyboard caused me a lot of grief but in the end i was able to tame the little bastard. some things to consider when modifying a pss-30; first of all there is a battery alarm tone that goes off something like every 90 seconds if the keyboard is not being played. overcoming this problem easily consumed a month of my time. though now that the issue is resolved i feel like the resolve was pretty obvious. in the end i had to devise a circuit that would continuously pulse a redundant function while the keyboard was not being played in order to reset the battery alarm timer. in doing this, i had to sacrifice the record and playback functions that the keyboard had, and whats worst, i had to sacrifice the rhythms too. i did have a plan to create a different circuit. in which case i would have been able to utilize the rhythms and be able to disable the drum circuit. however, i soon found that the little bastard keyboard had another trick in store for me. the keyboard's chip has two analogue audio outputs. one for the melody and one for the rhythms. however, the two separate channels have bleed through, and the signals can be heard through the others' respective channel. this was not acceptable because like most of my synth circuits these days, the melody voice runs through a frequency divider to generate sub-octaves. when the sound of snare hiss runs through the divider, the output is something like a crackling pop sound and it sucks! i had planned to add a step sequencer to the keyboard anyway, and since the melody section and the rhythm section are on the same clock, it would have been hard to make any sense out of the rhythms constantly pitching up and down. i decided to add a separate drum circuit. i had a couple of these cheap drum machine key-chains that had some pretty nice drum samples in them. i figured i would build a crazy rhythm generator that triggered the sounds, and mix that with the sounds of the pss-30. i found this schematic somewhere that used the cd4089 binary rate multiplier as a pattern generator. i figured i would use those to trigger the drum sounds through a web of dividers and synced to the step sequencer's clock. i built it all and it sounded great. i have to say though, it was kind of odd to hear clean realistic drum sounds against the shredding sub-octaves from the pss-30. i went to work on the filter section of the pss-30. rather than using the usual noisy op-amp filters i usually use, i decided to give the lm13700 VCF a try. it was a little more work but i must say, the sound is way better then any other filter ive built. i figured out a sneaky way to steal a little current from the key matrix of the pss-30 and turn it into a trigger without disturbing the functionality of the keyboard. i used that signal to trigger the envelope generator that modulates the cutt-off of the filter. now that the synth is finished, i do regret not putting in a more sophisticated envelope generator. it works but its range is low. oh well, its great at what it does. next i built the step sequencer. in the past i have always used the cd4017 chip for sequencers but this time i wanted to have the ability to run the sequencer up or down, so i drew something up using the 74hc193 counter and the a cd4051 analogue switch. it turned out great! i could run the sequencer in both directions and i was able to do other things too. i added a feature that would hold the last step in the sequence until the the keyboard is inactive, and i added another feature that gates the sequencer from the first step every time a key is pressed. i even added a rotary encoder circuit to be able to jog up and down in "program" mode to individually tune each step or to just transpose the keyboard quickly. i gave the sequencer its own cd4089 pattern generator and moved on to incorporating the melody and rhythm circuits together. ok, so reading back a bit i realize that i have not mentioned how long i have been working on this project and how many shitty and/or distracting things have happened to me. by this time in the project i am going to say that it is probably around july... anyway, so i am going back to the drum circuit in all its glory and i want to put all these circuits together. unfortunately the drum circuit doesnt work any more. after spending a week or two trying to figure out why it suddenly doesnt work any more and replacing everything including the drum circuit its self, i came to the conclusion that it was totally fucked. i was left with a big hunk of circuits and two fried drum toys. not a problem. by this point im so fucking jaded that it doesnt even bother me. and for some reason the dude who i am building this for is not bothered that i have spent six months on this shit and there is no end in sight! sweet... all the while i am thinking of all the other stuff i'd rather be building. so i take a little break and do a rebuild of one of my older projects that i sold to another guy some years ago. more details in the previous post. 

 

(dead drum) 

after a much needed break from this project, i came back refreshed and decided to use an analogue drum sound generator. why not? it would sound great with  the pss-30. i grabbed a little KoolShades drum machine from the basement and reverse engineered it. i decided that each of the four drum sounds should have its own pattern generator, pattern divider, volume control, and accent control. on top of that there is a pattern reset switch for each of the pattern generators to be able to sync or de-synchronize patterns from each other. there is also one "all" reset switch that resets all of the five patterns at once. it came together really well. by this time in the project i was unstoppable. if an issue came up, i knew what the problem was without even looking at it, and before i knew it, the circuit was built.

 

now i had to think about the case. after the mess with the cabinet and the tolex i was just not satisfied with the edges of the case. i figured i would find some kind of decorative edging to cover the seams of my amateur upholstery job, but when i hit up google i was left disappointed. now i really must say that this was definitely the most emotional part of the project. i could not for the life of me find anything remotely close to what i was looking for for a whole month! and its all i did for the whole month too! i was consumed. all i wanted was some of that cheap shiny edging that you see everywhere on everything... why couldn't i find it? what is it even called? after a month of wasted hours of google searching and bad dreams about it all, i finally found this thin steel tape that is apparently used for tagging machine parts in big dirty shops. the stuff is crazy durable and polished, and very flexible. this would have to do.

next up; faceplate. designing the faceplate and the whole interface was really fun and pretty easy. i sent my design to pololu to have them cut it like i have before in the past, and began work on designing my graphics. when the faceplate came, it was opposite the direction i needed it so they sent me another one no charge. sweet! now i have two. 

sad to say though i probably wont send any more designs their way since i have a laser of my own now. now that i had the right faceplate i needed to think about how i would apply my graphics. for some reason i thought that vinyl was an option. hahaw. no, vinyl was no option. i then started looking in to companies that offered dry transfer services but that shit is offensively expensive. after wasting more time on dead ends and being offended by returned quotes, i landed on screen printing. i had never screen printed anything before but how hard could it be to screen print 12" by 12" of 8pt text on a smooth surface? well, its pretty fucking hard. i bought all the stuff and did some trials and after being totally frustrated by it all, decided to just go for it. the result was actually way better than i would have expected. there are a lot of fat smudgy parts, but all in all it passes. 

at this point in the project i was pretty distracted with traveling to new cool places with my GF so it was kind of slow to wrap up. i gave the project a few hours of my day each day before work and a little more on my days off. once the wretched holidays were over i put it all together like a puzzle. and so here we are. almost a year later and i'm left with a big beautiful symbol of the last year of my life that i cant remember very well. check out the demo video for more details. as always, click on the pictures for larger sizes. 

 

CIRCUIT BENT GLITCH SYNTH REVISED

this will be a quick write up on a project i finished a while ago. i've been meaning to post this for a while but have been preoccupied with other things. this project came to me while i was working on a much larger project. i needed a break from the larger project and a piece i had sold someone a long time ago had fallen on hard times. the guy i had sold the keyboard to has bought many things from me over the years. he contacted me to let me know that the glitch circuit in the keyboard was no longer working. he asked if i could fix it and i agreed. the keyboard was a glitch toy that i had built in 2008 and sold on ebay. more details here.

 (this is a photo of the original mod)

upon receiving the keyboard in the mail, i was pretty stoked to see one of my earlier creations again. i couldn't believe how long it took me to build that piece of junk. the functions were silly! i opened it up to have a look at the glitch circuit. it was dead. i don't really know how or why but it isn't the first time that i've seen a glitch circuit just stop glitching. the glitch chip that i used in the keyboard came from this funny toy that had great sounds and produced very unique glitch sequences. and quite a few more types of glitches than your standard 3 volt glitch toy. it was hard to accept that it would not glitch ever again, but i did have an alternative. the yellow toy steering wheel that i have used in so many of my other glitch toys is usually the easiest to find of 3 volt glitch toys and in my opinion the most consistent. the fix would be simple. i would replace the glitch circuit, send the keyboard back, and get back to the torture of my other big project... only problem was that by replacing the glitch circuit, most of the buttons and some other functions on the keyboard would be rendered useless. not only that but i was kind of appalled by the wiring of the whole thing. i offered the owner a deal he couldn't refuse. i would completely overhaul the whole thing for the cost of materials. he agreed and i had something new to distract me from the frustration of my other project. the first thing i did was completely gut everything. 

i began developing a new circuit based on one that i had prototyped a while back. basically a glitch circuit that does not require the user to activate a sound, then glitch it, and then reset it when it locks up. it is basically a step sequencer that is activated with the push of a button. when held, the sequence will start by activating a sound, then glitching the sound, and after a second or two will reset the glitch circuit and start the sequence over. this makes it easier to find the glitch you are looking for. all you have to do is hold down the glitch button until you hear the glitches that you like. 

   

that easy button freed up a lot of space on the control panel for other things so i decided to run the glitch generator through a frequency divider and have three independent channels each with their own volume control and resonant filter. there is also a clean mix that is a volume control for the original glitch signal. the third sub-octave channel also has a six-position switch that can select one of six sub-octaves. the lowest of which is more or less a clicker. the output of the divide channels is substantially fuzzy because the signal needs to be "squared up" before it can be divided, so the sub-octaves are quite a bit harsher than the original signal. i also added a switch to send the piano sounds into the divider to be mixed with the glitch signal before it is divided or to be divided by itself and mixed back together. there is a switch to mix the original piano signal with the sub-octaves or mix the sub-octaves alone without the original signal. 

 

(hardware mock up)

 

(hardware mounted)

 (all wired up)

there is also a guitar input to the divider, however the original signal from the guitar input can not be mixed in. all three inputs(glitch, piano, guitar) are mixed together prior to dividing so some really complex noise textures can be achieved when the three are playing together. the modulation is all the same except i completely rebuilt the two LFO's. they originally had been pretty limited in range.  i rewired all of the hardware and gave the piece some nicer knobs too. see the manual i made for more details on the modulation.

 

that's about it...

HARTMAN ENVELOPE FILTER MOD JOB

 

this is a commission i took on about a month and a half ago. the idea was simple really. a friend of a friend wanted to add an expression pedal to his Hartman envelope filter. after doing some quick research on the Hartman, i found that it is a clone of the famous mutronIII pedal. rather than just agreeing to add a simple expression pedal to open and close the filter, i suggested that he(the owner) have me add as many mods as possible. i suggested adding the three missing filter modes highpass, bandpass and notch filter outs. i also suggested adding attack/release controls for the envelope, and a multi-shape lfo to modulate the filter. i gave the owner a pretty reasonable quote for the commission and he agreed to go for it. initially i thought that this project would not take more than a couple of weeks to finish. as always, i was sorely mistaken. first of all drawing out the schematic alone took an entire day. the pcb is double sided. i thought it would be identical to the mutronIII schematic, and later i found that for the most part it was, but the way the circuit was laid out, the only thing i could recognize was the filter. i had to redraw the rest of the circuit point to point only to find that the envelope generator was the same too. the only thing Hartman seemed to add was a mixing buffer to be able to mix between dry and wet, and some kind of power conditioner that i don't fully understand. see my original drawing  for more into that...
 
 another issue i had with the Hartman circuit is that it just seemed to be very cheaply constructed. apparently this particular model was a prototype. it had numerous extra parts and wires that went nowhere or were redundant. i thought that was kind of cool. i however didn't think it was very cool that the solder used in this thing seemed to be either lead free or flux free. either way, that shit was awful. it was all dry and crusty and it would "infect" any fresh solder i would add. another thing was that the traces on the pcb were extremely thin and fragile. they could be scratched right off with no effort. the wires coming off of the pcb to the hardware broke and had to be reattached so many time that eventually i just replaced the worst ones with solid copper wire. despite all my gripes with having to work around someone Else's work, the circuit sounded pretty great. i came up with a plan that i thought might work, and drew up a schematic for the mods that would be added. i picked up this vco chip years ago and I've been meaning to use it. its called the icl8038 and from what i understood, it is a pretty nice function generator chip with sine, pulse,and ramp outs. i thought it might be cool to be able to modulate the filter with the lfo and then use the envelope from the Hartman to modulate the depth, rate or duty ratio of the oscillator, as well as being able to control all of those parameters in addition to the wah filter via the expression pedal. i had planned to put all of the additional circuitry in the expression pedal itself. in order to get those 16 connections that i would need from the expression pedal to the Hartman, i would need my old friend the MDR cable. fortunately too i was actually able to find one at goodwill for only $5. the only catch was that it was attached to a floppy disk drive. an MDR cable is a Mini D Ribbon cable and they are awesome! they can carry as many as 40 leads and they have these wonderful squeeze-lock connectors  that are super strong. i would love to know where i can find more of these. i found them on mouser but they are non-stocked. they are super rare  to find in thrift stores too. everything is usb now so the old floppy drives that employed them are probably all off to the recycling. if you know where to find MDR cables with the quick release connectors, please let me know.

one thought that crossed my mind is that in order to reroute mods from the Hartman to the expression pedal, the original functions would be disabled when the expression pedal is disconnected from the hartman. i came up with a plan to have all of the mods switched to the the expression pedal through a cd4066 digital switch that would activate when the connector is in. it was a pretty slick feature. unplugged the Hartman would be stock, plugged in, the expression pedal would take over. sadly though, one of the leads that the 4066 was responsible for switching was the -9volts which the 4066 didn't appreciate very much seeing as how it was running off +9 and ground, and it died on me. i considered running the 4066 off ground and -9, but the input for the switch was the ground. i figured no matter what solution i came up with to be able to use 4066, it would inevitably die anyway. they always do. so i ripped out all my work and replaced it with 4 pole switch. its not nearly as slick, but just in case something awful happens to the exp. pedal rendering it useless, the Hartman can still be used as it was originally intended.

 
coming into this project i have to say, i didn't know that much about Vactrols. the Hartman filter is modulated via matched vactrols. vactrols are basically an led stuck to a light dependent resistor encapsulated in a light proof box. the more light, the less resistance. i picked up quite a few vactrols for a good deal a while back and i thought i would use them for this project. in my original schematic i had planned to to implement all of my mods with their own respective vactrols. i soon found that not all vactrols are the same. all vacrtols exhibit some latency, even the fastest ones. the vactrols take noticeable amount of time to peak and disengage when the current to the led is cut off. the vactrols in the Hartman are pretty fast but the vactrols i have are painfully slow to disengage. i had to go back and reconfigure my schematic to use only the vactrols already in the Hartman to modulate the filter with the expression pedal and lfo. the other vactrols and optoisolators i used for modulating the lfo parameters are not as important as the response from the lfo or pedal to the Hartman filter. although the lfo modulates the filter via the original vactrols, they still exhibit latency too. i noticed that at higher lfo frequencies the filter would stay closed because the vactrols wouldn't have enough time to disengage. and the frequencies weren't even that high... i had no choice but to literally rectify the situation. the vactrol cathodes go to ground and not -9 volts. this is how it has to be in order to be able to invert the envelope with the direction switch. the signal from the lfo would have to be half wave rectified. i tried to run the lfo off of 9v and ground but it wouldn't oscillate. below is a diagram of whats coming out of the lfo(left), and what is modulating the filter(right). those shapes are probably distorted too because of the latency of the vactrols(i can only assume without plugging it into an oscope).


so yeah, the wave shape names on the side of the expression pedal are totally false but still quite usable. who knows, maybe the solution will come to me before i ship it out on monday. oh yeah, did i mention that the icl8038 didn't work out? yeah, that was supposed to be before all the vactrol nonsense. so the icl8083 is basically a piece of shit that is worthless in more ways then i care to mention... actually its not that bad. I'll just never use one for anything. instead i found this super simple tri-shape lfo schematic built around a quad op-amp. it works great and i am sure i will be using it much more in the future.

ok, where am i going with this? i guess now is where i describe the finished pedal. i painted the base of the roland EV-5 pedal orange and applied white lettering for the parameter labels. i then finished it with clear lacquer.

the PED switch assigns the expression pedal to the lfo rate, lfo depth, filter or off. the MODE switch selects the filter type highpass, bandpass, lowpass, or notchpass. the silver knob sets the maximum depth of the expression pedal.
 
 the ENV switch assigns the Hartman envelope to the lfo rate, lfo depth, filter or off. the the LFO switch selects ramp, square,sine, or none waveshapes. the toggle switch under the expression pedal switches between stock Hartman envelope and custom envelope. the two pots control the attack and release of the custom envelope when engaged.
 
 the DEPTH and RATE knobs control depth and rate or initial depth and rate of the lfo.





 this is a sort of diagram for how it all works

 here are some pictures of the inside of the finished pedal prior to some extensive debugging.

 her is a crappy video i threw together. its too hard to try and play guitar, shoot a video and tweak a pedal at the same time so i just ran my omnichord through it. I'll try to make a better demo if i have time.

thanks for reading/watching.
-tanner