wow, its been a long time since i have posted anything here. i have mostly just been doing custom projects and odd jobs for people for the last couple of months. nothing worth posting. actually, now that i think about it i probably should have... oh well. this most recent project is definitely worth blogging about. this piece was a commission for a loyal enthusiast and valued customer of mine. i cant remember what the original criteria for the synth was exactly. im not even sure if i came close but hey, this is a sweet synth.
the synth is based around a very generic toy organ chip. i used the same chip in my "rainbow synth". the main voice is sent to an envelope follower for the attack release generator and also to a frequency divider where it is divided 8 times. each octave has a volume control on one of two axis of a joystick. the 8 octaves are then mixed back into the filter. the filter can also be modulated by one or two LFO's: LFO1, or LFO2 gated by LFO1. changing the GATE TIME pot on the AR generator will alter the AR generators response to the LFO as well, giving it even more diverse trigger sequences. the two LFO's also trigger the 8 step sequencer. you can choose LFO1 or LFO2 gated by LFO1. there is also a switch to allow the sequencer to be triggered by the main VCO just after the frequency divider. this makes for some INSANE timbres. this particular toy organ chip has got a few irritating setbacks. for one, in order to get 8 good sounding octaves from the divider, the chip has to be clocked pretty high, which is good because the action was pretty slow, but there was this sleep timer that went off literally 1 second after hitting a note. i built a simple lfo and sent it off to some redundant IO. it did the trick. another problem was the key hold. every keyboard with a sequencer should have a key hold switch to hold down the last key you pressed. usually you can just wire a switch to an unused key and it will switch to whatever key you press last. not this one though. it holds one key and one key only. i used a 12pos rotary switch for the key hold on this one. 9 of the 12 positions are connected to f#,g,g#,a,a#,b,c,c#,d. they can also be switched to a,a#,b,c,c#,d,d#,e,f of one octave lower. all issues fixed, this is sweet sounding little synth, especially with the added echo circuit. i had a few pt2399s laying around so i figured id throw one in. it is pretty excellent. i think i'll put a pt2399 in all of my projects from now on.
so from left to right the functions include; SEQUENCER switch with led indicator OFF>LFO1>LFO2viaLFO1, 8 step sequencer pots, VCF switch with led envelope indicator ECF>LFO1>LFO2viaLFO1, LFO1&2 pots, AR gate time pot, attack pot, EG depth pot, release pot, resonance pot, cutoff pot, power switch OFF>ON>ON/KEY HOLD OCT^, master volume, pitch bend, key press indicator led, main VCO trigger sequencer ON>OFF, echo feedback pot, echo rate pot, 4 joysticks for 8 sub octaves, rotary KEYHOLD switch, and finally a 1/4" line out.
this keyboard was all fitted into a travel size backgammon case that i found at goodwill. its actually pretty decent quality pleather. the panel was BOUGHT... yeah, first time ive ever had a piece of plastic cut to order. it was actually pretty easy. in fact it was a hell of a lot easier than cutting it by hand. only problem is it cost $50. ouch...
uuuhhh. ok, i feel like ive been typing forever even though ive only got like two paragraphs. forgive my A.D.D but its beer time. here are the pics and video. please comment.