TOG, Top Octave Generator DIY (Mostek MK50240 emulation)

delayed · Joined: Jun 24, 2008 Posts: 130 Location: TN

does anyone have the pnp blue layout for these? the link on the top is dead.

sizone · Posted: Wed Jan 25, 2012 2:51 am Post subject:

Just finished the circuit for my mono version of this. Will post the connections after I draw them up. Basics is that it's a 23 key keyboard (bottom C would've required either sacrificing several octaves of range or putting in way more extra circuitry than it would be worth. In case you're wondering why it's because you can't get a close enough division for it (c8 or c7, can't remember which) from 2mhz with the 4040) with a 4 position octave selector switch. Chips used are the 4046, 2 4040s, a 4051 and, currently, 1/6th of a 4069 (don't worry, I'll at least use the other ins for lfos and an always useful inverted square wave). Everything's pretty much straight-from-the-datasheet straight forward. Only really clever (alright, at least by my standards) thing I did was to split the reset pin output on the 4040 going to the keyboard switch array into a separate output for each octave, then take a lead from the lower octave and run it to the 4069 so that the voltage drop when a key is depressed (in that octave) triggers a high out on the 4069 which is routed to the A control of the 4051......ummmm...it'll probably make more sense in the drawing.

Playing will probably sound better after I glue my freshly cut lexan strips over the switches.

Wish I'd had the foresight to pick up some IC sockets today when I was getting my perfboard so that I could start transferring this to the perfboard.

Oh, also of note is that the plastic VHS case that the switches are glued to was found on the side of the road. The tape it contained had 80's porn on it. Thought you should know.

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inlifeindeath · Joined: Apr 02, 2010 Posts: 316 Location: Albuquerque, NM

nice dude! looking forward to seeing this thing

bod · Joined: Apr 28, 2009 Posts: 148 Location: Glasgow

i finally got round to starting this project, thanks for the schematics Marco!! Very Happy

took about 11 hours to build the TOG board, now to work on wave shapers, EG, VCF and VCA per voice......

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Cynosure · Posted: Thu May 10, 2012 5:42 am Post subject:

Wow bod. Very clean and organised work. I didn't follow this schematic, but my top octave synth was a little messier...

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bod · Joined: Apr 28, 2009 Posts: 148 Location: Glasgow

good work! thats some rats nest!! to be fair mine will end up the same in all likelihood!

think i'm going to aim for an LM13700 hp/bp/lp vcf and vac for each note, but i need to work out a simple voltage controlled a/r envelope generator first.

AnalogCustom · Joined: Jun 23, 2009 Posts: 52 Location: Chile

Cynosure · Posted: Thu Jun 14, 2012 7:42 am Post subject:

Analog Custom - I was hoping to try your mk50240 emulation for my next top octave synth, but all the images are gone. Can you please repost them? You should be able to upload them directly to the forum instead of hosting on another site.

AnalogCustom · Joined: Jun 23, 2009 Posts: 52 Location: Chile

Hi:
Here the full access to all information, including files .pcb and "Protel PCB program" (old 1.5 version) to make changes on the pcb. Soon try to upload the information to this site.

https://docs.google.com/folder/d/0B8HNN2LiZQlGNS03ekJDMnZ5ZUU/edit

Marco