Monosynth with a weird control scheme

[Taylor]

So, I want to build a simple little tone generator with an unusual keyboard. Rather than having keys which always play a particular note (like a typical keyboard, where A is always A, etc.), it would have keys for +1 semitone, +3 semitones, and so forth. The keys would be latching switches with resistors attached which independantly raised the pitch of the note (which would by default be playing constantly, though there would be an on/off for the base note) by a certain interval, and when pressed again, would lower the note by the same interval (by bypassing the resistor). By turning on several keys at a time, many pitches could be played, over several octaves. There would be a pot for tuning, which would set the base frequency, as well as an on/off for the base note and a waveform selector.

Can someone point me in the direction of a good tone generator for this? I know about the 555, but it seems like it can only do a square wave. A few years ago when I knew more about this sort of stuff I was planning to make a ring modulator using an Exar 8038 since it has outputs for square sine and triangle, but I never got far enough to know whether it has any drawbacks like current consumption (ideally, I'd like this thing to be able to run on batteries). Is the 8038 a good choice, or is there something better? And can someone point me towards a good layout? Thanks

[caress]

check out some of the links from this thread...thomas henry's book might be a good place to look.
http://www.diystompboxes.com/smfforum/index.php?topic=57211.msg452723#msg452723

[Taylor]

Thanks. Does anyone know where to get 8038s? I can't find them at Mouser or Jameco, and I tried at one point to get some samples from Exar, but they don't give them up very easily.

Would I need to build some sort of power supply for this:

http://electro-music.com/forum/topic-17762.html

? Maybe I'm in over my head here. What's the deal with some resistors being labeled in Ohms rather than farads?

[Paul Perry (Frostwave)]

JDR microdevices has them at $8. http://www.jdr.com

But, maybe they have slipped out of production. End of an era, if they have. I have a bunch, but I don't like them much.

[caress]

paul, would you be willing to part with a few?  i'm really interested in experimenting a bit...

[Taylor]

How can I figure out what resistor values will raise the pitch 1 semitone, 2 semitones, etc.?

[Ge_Whiz]

The 8038 was superseded by the MAX038 some years ago.

Ohms = resistors; farads = capacitors.

How can I figure out what resistor values will raise the pitch 1 semitone, 2 semitones, etc.?

Experiment with a variable resistor (potentiometer).

[Paul Perry (Frostwave)]

The 8038 was superseded by the MAX038 some years ago.

Here's some bad news from Maxim:
"This product was manufactured for Maxim by an outside wafer foundry using a process that is no longer available. It is not recommended for new designs. For further information, contact us. The data sheet remains available for existing users."

Maxim are, of course, the company that very proudly said they would never let any chip of theirs go out of production.
Then they said that if demand warrented, they would keep chips active.
Now........

[Tim Escobedo]

There are dozens of synth DIY pages out there, and some decent kits, such as PAIA's. Though the learning curve may be a bit steep, it is probably easier to to go this route than reinvent the wheel. Such exponential voltage controlled oscillators also greatly simplify devising an unusual keyboard controller.