Tuesday, February 24, 2009
RHYTHM MACHINE FINISHED...
well its been a long week. after spending about 14 hours putting all the circuitry together on friday, i took a 3 day break for my day job. it was quite the wait. i thought that if the circuits all went to plan, i would have a new keyboard by friday night, but naturally some things didnt work. in a nutshell, the filter/amplifier module was wrong(i still dont understand why), i drew up the keyboard's schematic wrong in some places(three times), and some of the lfo mods that i didnt breadboard first didnt work at all. i put in a few hours before and after work over the weekend, but it wasn't until today that i wrapped this project up. i rebuilt the amplifier/vcf module and fixed the errors i had made with the schematic. i put it all on bread board before i built the module again. it was exactly the same as the first one. i still dont understand why the first one didnt work. the second lfo that was supposed to modulate the pitch bend didnt go deep enough and raised the minimum pitch too much to have a coarse and fine pitch bend. instead i sent the square output to the vcf so now you can modulate it with either ramp or/and square. i also got rid of the feedback function and used the pot to cap the depth of the square vcf mod. there was some bad buzzing coming from this keyboard. i knew it was there the whole time. thats just the price you pay when combining toys and single supply vcf's, but when i put it back together it was much louder. i went back in and found that the filter/amp section needed to be further away from the keypad. i had to UNGLUE it! i hate ungluing! i pulled it away and wrapped it in electrical tape(not sure if that does anything) and now the sound is as faint if not more so than when i prototyped the circuit. there are still some things i have to fix though. the lfo pots that trigger the cowbell and bass drum also control the vcf modulation. the switches that turn the triggers on and off are supposed to be right next to their respective knobs, but for some reason the switch for the bass drum is next to the cowbell pot and viceversa. also the square signal that is modulating the vcf is a little too strong. you can hear an annoying click when you turn the speed up. i also need to fix the 1/4" line out. it sounded kind of squirly when i hooked it up to my computer. i'm sure its an easy fix. here are some pictures of the assembly.
the video is pretty uninformative because my camera ran out of batteries and space. i hope its audible.