Harmonic/Overtone Series CMOS divisions

[hellohelloetc]

Hi all,

Long time reader, 1st time writer.

Does anyone know of any IC that'll output 1/2, 1/3, 1/4, 1/5, 1/6, 1/7.. etc? Hopefully I'm describing this in the right way. Basically dividing a clock by the first few integers, with a 50% duty cycle. Essentially the overtone series.

I've been hunting around for a while, to see if anyone else has done something similar here before, but haven't had any luck finding anything (perhaps my searching is at fault though).

At a guess I could use a combination of a cd4040, and a cd4018 could at least get me 1/2, 1/3, & 1/4

Either way, I'll post a schem here once I figure it out, but any pointers/thoughts would be super appreciated

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[blue hell]

hellolohello

Maybe look at rate multipliers, they actually divide ... maybe not in the pattern you envision though.

[PHOBoS]

I think you could just use a decimal counter and set the number of steps to get the divisions. That won't give you a 50/50 dutycyle
so you'd to divide it by 2 after that, of course the downside is that you need a higher frequency to begin with.

if you use a mulitplexer to set the number of steps you end up with the infamous 4017/4051 melody generator (though that one doesn't have a 50/50 dutycycle)
or you can go larger with the Melody Generator XL. In that thread things got a bit out of hand and I ended up with a full chromatic version.

a Rate Multiplyer is nice but has the output pulses unevenly spaced (at least the CD4089), very useful as a rhythm generator though.

something else that might be of interest is Symmetrical Digital Dividers

[dk]

Welcome!

As PHOBoS said, you can use a decimal counter like the 4017 and divide the outputs by 2 to get your 50% duty cycle, perhaps using a PLL in front of that to not drop the new pitches too far below the original note using an arrangement like Scott Gravenhorst has here: https://electro-music.com/wiki/pmwiki.php?n=Schematics.PLLFREQUENCYMULTIPLIERMODULE

[hellohelloetc]

Thanks for all your wonderful answers, you're all very kind

I've never quite gotten my head around phase locked loops, but I'll start digging into them again. In my day job it's all relay logic, so it's a starting place, but the logic is fairly basic. I've been picking through the CMOS cookbook and making notes, most of the chips that aren't just standalone gates take me a bit of staring blankly until I click on what it actually does... but I'm getting there!

You've all given me some great directions to start investigating, and I really appreciate it

My vision is for a some kind of thing that allows me to mix overtones, a pot for each overtone up to about the 7th.

Thanks again!

[PHOBoS]

are you familiar with the Harmonic Engine (E&MM Harmony Generator clone) ?
I haven't come across the CD4526 yet but there are other ways. I did drew up a circuit to use a CD4522 instead but I have no idea if that would work.

[hellohelloetc]

Thanks PHOBoS, I wasn't aware of the Harmonic Engine, looks pretty interesting.

It just hit me that my approach & sketch are not the overtone series at all. I don't know exactly what it is, it'd be interesting to hear it, but it's not the overtone series.

My original sketch starts with a higher frequency, then increases the wavelength by 2x, 3x, 4x etc. My initial thinking was that I'd start with a higher frequency oscillator and CMOS it down to some aimed-at fundamental - which is not what that sketch of mine was doing.

It looks more difficult now, but I'll keep chewing on it. I think the approach of starting with a higher freq oscillation, then CMOS-ing it (not yet sure of the correct division/multiplication terminology) to various lower frequencies is more tricky.

As I see it, if I want to have all the overtones up to the 7th, I would require a source frequency that is 5040x the fundamental, which is 7! (1x2x3x4x5x6x7). This would be the lowest relative frequency that includes all the transition points of the overtones up to 7. Then the problem becomes, how to get wavelengths that are:
630x source, 720x source, 840x source, 1008x source, 1260x source, 1680x source, & 2520x source.

All of this makes me think I need to totally rethink my approach, lol.

Thanks again for all the great suggestions

[blue hell]

still interesting though: https://en.wikipedia.org/wiki/Undertone_series and https://en.wikipedia.org/wiki/Subharmonic_synthesizer

And re. overtone mixing - when all the harmonics are obtained from one source there will be a fixed relation between them which may sound a bit static. Using a PLL there may be a bit more dynamics though, as the coupling is a bit elastic then - it will take some time before sync is reached, it may even be jittery depending on the filter used.

Then another thing .. you could look at organ dividers (top octave synthesizers) .. which start at a very high freqency and then everything is diveded dow (but according to (an approximation of) a chromatic scale (12TET).

[hellohelloetc]

Cheers Mr. Hell

Subharmonics sound interesting. I'm reading my way through some PLL stuff now.

I hate to say it, but I just went and programmed an arduino to do what I wanted. How boring lol, still would prefer to figure out how to do it with CMOS. I figure since it's pure/pythagorian harmony, rather than equal temperament, the relative pitches maybe a little easier to get to.

[zaphod betamax]

The CD4526 seems hard to get.
Apparently, according the CMOS cookbook the 74xx161,2,3
are basically a replacement as long as you don't mind +5V as Vdd