This is a project I'm having at school. Currently only the plans are complete, the practical work have only just begun. This is going to be an analog two-oscillator synth with keyboard and lots of knobs. It'll be built around Curtis chips; one 3374 dual VCO and one 3378 VCF+VCA. In addition it'll have one LFO, noise and even a joystick. :-) It won't have MIDI, not yet anyway. It will be rather big because I want to have room to expand it, maybe with two more VCO's? Things are looking bright, I just got the CEM's and the old organ keyboard is just waiting.
More info will come. Promise.
Status per 15. February:
Have started making PCB layouts with a trial version of Protel 98.
Nice program. Way too complicated though. But it gets on. Have also started
writing software for the Motorola 60HC705 microcontroller keyboard scanner.
First version didn't work well. Hard to simulate tho. Will make PCB for
the scanner too soon. BTW: Front panel layout is done. I've made them with
Paint Shop Pro 5 (demo version :-).
And 19. February:
Got the front panels transfered to film today. Looks good. Got myself
42 diodes soldered on the keyboard.
Per 1.March:
I've been a-working on PCBs - two is done: LFO/Glide/Noise and 2x VCO.
These I have designed and etched. Came out pretty well me thinks. I have
begun soldering them. Also I have designed the VCF board. I feel I'm getting
better at it, the VCF is neater than the two first. Coming up: Envelope
generators and (hopefully) the µC keyboard scanner. Assembler code
for the keyscanner is done, needs to be tested. Still haven't got the fromt
panel films fastened onto the aluminium front palels tho.
Here we go again... 6.March
Been attending ToTo concert - also been working on cabinet. It is HUGE!
I suprised myself; I never visualised its size. 1m across, 64 cm deep and
40 cm high... doesn't sound like a lot, but I realize this'll be a monster
to carry around. But that's OK. Furthermore, I've made this Nebulus Now!
button. Use it! 
(Oh well, it was fun to make.)
Hi again - 25.March
I have completed the dual VCO - it works!! Haven't tried to calibrate
it or anything, just viewed the waveforms on my old vacuum-tube scope.
Neat. Have completed the LFO, too. Works, but the noise source is mot OK
yet. The VCF/VCA board is soldered and ready for testing. The dual Envelope
Generator is ready for testing as well. Did I mention I decided to use
the voltage controlled HADSR circuit designed by Jürgen
Haible instead of my own - and Jorgen Bergfors has designed a fab PCB
for it - in Corel draw! Neat! Had to make a new front panel for that extra
"Hold" pot, tho. BTW, I used double-stick tape to fasten the transparent
films to the aluminium panels. Furthermore, I have made the PCBs for the
µC keyboard scanner thingy - I shure hope it works! And PCB for the
joystick. The future is bright - the future is Nebulus!
27. March
I just tested the VCF together with the VCO. It worked! Had an astonishing
amount of DC offset at the output, but I suppose I'll get rid of that somehow
sometime. Also I put together the case - MAN it is SO cool. and SO BIG!
Well, it culd have been a lot cooler if I had had just a hint of woodworking
skill.... but I think it is rigid enough. We'll see.
15. April
Hullo, and welcome back! Many things has been done since last time.....
I've made the VC HADSR work OK, t'was a bit trouble with it at first. I've
mounted the PCBs to their front panels - one word: superglue. Another word:
mess. (c8 But it's OK. I'm almost ready to patch it together now. I've
made a hatch in the back so that I can access the electronics without removing
the front panels. Well... got to go to bed. CUL8R yea.
18. April
Got into the Synth-DIY webring..... sure hope it works. :-)
30. April
Horray! My synth is up and running, and actually working very well
according to plans. I used it last saturday on a gig, actually, so it's
been operative for a week now. Changes: The superglue approach to fastening
the PCBs didn't work at all. The only module that has kept the glued-on
screws so far is the VC HADSR envelope generator. The rest had to get drilled.
Oh well. The VCO electronics was slightly modified: I changed the cap value
in the AC coupling on the Linear FM input. One dissapointing change: I
had do drop the microcontroller keyboard scanner thingy because the school's
EPROM burner/programming equipment has gone out of order. So I used Tom
G's analog keyboard scanner instead. So there'll be no arpeggiator (DOH
- i mean DOOOOH!!!), at least not yet. - The only thing
not yet completed is the joystick. My original circuit did not work. But
I've designed a new one that does. Now I only have to build it. Another
thing I'll have to do is to sample a bunch of sounds and take some pictures.
And write a report for the teachers at school. This is after all a school
project. Still.
11. May
Hullo, and welcome back. Tomorrow is thatday when I am going to have
my project evaluated. It is about as finished as I can get it (I keep running
out of time) but it'll get more features added when I get it back. Such
as Distortion, Reverb, and the joystick that still is not working.
13. May
Last entry. I'm fed up with this thing. Now at last everything works.
I'll be taking a looong break, if anyone needs me.
Bye.
