4520 Questions

oram · Joined: Jan 04, 2016 Posts: 3 Location: New York

Hi,

I'm new here. I recently posted an introduction.

I've built lot of guitar pedals and some amps, but I just started to get into this synth stuff, and have lots to learn.

I've been messing around with a breadboard and some 40106. I plan on experimenting with making a 40106 polyphonic keyboard. I was mostly reading about 4040 ICs but I just discovered the CD4520. Am I reading this correctly? Is it 2 separate dividers in one IC? If so, this would allow me to cut my divider IC count in half! As I only really need 3 or 4 octaves.

If so, and I just wanted to use this IC to simply divide 40106 oscillators, would I need to ground both Enable A/B and Reset A/B pins?

Also, I noticed that the 4040 IC does not have an Enable pin. What exactly does this do?

Thanks to all for the help!

PHOBoS · Posted: Tue Jan 05, 2016 9:49 am Post subject: Re: 4520 Questions

yes, the 4520 has 2 dividers/counters in one package which can be used independently. Both reset pins
need to be connected to GND, both enable pins need to be tied to V+. The enable pin enables the CLK input
so if it is low the CLK signal is not passed through to the counter.

If you really want to make a polyphonic keyboard I would advice you to read this thread. (if you haven't already)

oram · Joined: Jan 04, 2016 Posts: 3 Location: New York

Hey thanks so much for the reply! I did see that link you posted. Some cool ideas there for sure.

I've been bread boarding A bunch of ideas for the keyboard and it's all working pretty nicely.

Im slightly concerned about the pitch stability of the oscillators. So I'm looking into what would be the best type of caps to use. Especially with temperature sensitivity.

Also, I can use basic push button momentary switches. But keyboard keys would be nice. Anyone know of some cheap keyboards I can gut that use momentary keys? I opened a cheap 90s keyboard and the PCB on the keys use some weird diode scheme I can't get my head around. Nothing fancy, I just need totally independent keys for full-on polyphony!