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 Forum index » DIY Hardware and Software
Basic sequencer guidance
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nullpainter



Joined: Nov 07, 2011
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PostPosted: Mon Nov 07, 2011 11:41 am    Post subject: Basic sequencer guidance
Subject description: Just making sure I'm on the right track!
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Hi guys,

After a rather unsuccessful foray into electronics in my childhood, I'm pursuing it again by way of Nic Collins' 'Handmade Electronic Music' book. I'm making weekend projects based off the book as a way of practical experience and am trying to gradually ramp up the complexity.

I'm keen to try my hand at a very basic sequencer, but would like some guidance that I'm on the right track.

I was thinking of using a 4017 clocked by a 40106 to control the steps, with each output hooked up to customary LEDs and sliders to adjust the pitch. I'd really like the the pitch to be quantized; i.e, each slider switching sharply from A, to A#, to B, etc. when moved. Could a demultiplexer chip be used for this? Single input and multiple outputs depending on voltage?

I was then thinking of connecting trimpots to the multiple outputs to tune the output of another 40106, and maybe adding some sort of primitive filter at the end.

So, three questions:

1. Is a demultiplexer what I'm after?

2. Do you guys reckon that I'm on the right track? I'm pretty fresh-faced when it comes to designing circuits.

3. I see the 4046 VCO chip mentioned, and an indication that it's really versatile and "underpins traditional analog synthesizers". Is it worth giving this a go? If so, would I need to implement voltage divider type arrangements in combination with the tuning trimpots?

Thanks,
Matt
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nullpainter



Joined: Nov 07, 2011
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PostPosted: Mon Nov 07, 2011 11:43 am    Post subject: Re: Basic sequencer guidance
Subject description: Just making sure I'm on the right track!
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nullpainter wrote:
Could a demultiplexer chip be used for this? Single input and multiple outputs depending on voltage?


Actually, I think I've completely misunderstood how mutliplexers/demultiplexers work. Are there any quantising chips out there? It seems a sensible thing to exist in the wild, but quick Googling doesn't come up with much.
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Antimon



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PostPosted: Mon Nov 07, 2011 3:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

welcome nullpainter!

I don't have any answers for you, I just want to point out that if you post this kind of question in the DIY there is a very high chance that you will get some awesome answers. Possibly a mod will move this thread there in time.

Good luck!

/Stefan

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nullpainter



Joined: Nov 07, 2011
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Location: Wellington, New Zealand

PostPosted: Mon Nov 07, 2011 3:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Antimon wrote:

I don't have any answers for you, I just want to point out that if you post this kind of question in the DIY there is a very high chance that you will get some awesome answers. Possibly a mod will move this thread there in time.


Oh, bother! Thought I had posted in the right forum, but clearly haven't. I'll wait for a friendly mod rather than double-posting. Thanks for the heads-up Smile
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Blue Hell
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PostPosted: Mon Nov 07, 2011 3:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

Cool There it goes ... landed in DIY Laughing

Thanks Stefan and welcome nullpainter.

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nullpainter



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PostPosted: Mon Nov 07, 2011 3:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

Blue Hell wrote:
Cool There it goes ... landed in DIY Laughing

Thanks Stefan and welcome nullpainter.


Cheers Blue Hell Smile
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Blue Hell
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PostPosted: Mon Nov 07, 2011 3:22 pm    Post subject: Re: Basic sequencer guidance
Subject description: Just making sure I'm on the right track!
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nullpainter wrote:
Are there any quantising chips out there? It seems a sensible thing to exist in the wild, but quick Googling doesn't come up with much.


Yeah there are - look for AD converters, it'll need some trickery to get the scaling right, but you may find some example circuits for it.

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nullpainter



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PostPosted: Mon Nov 07, 2011 3:44 pm    Post subject: Re: Basic sequencer guidance
Subject description: Just making sure I'm on the right track!
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Blue Hell wrote:
Yeah there are - look for AD converters, it'll need some trickery to get the scaling right, but you may find some example circuits for it.


Ah ha! That looks like the ticket. Thanks!
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nullpainter



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PostPosted: Mon Nov 07, 2011 5:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

The only ADC chip that seems to be sold by my local retailer is the ADS0804, which (sensibly, I suppose) seems to spit out binary data. I think. I'm still finding product sheets a touch intimidating...

I was previously thinking that assuming I have X different notes, I would have X tuning trimpots in order to tune each note and therefore something which has X different outputs.

Maybe I'm over-simplifying the problem. I suppose I could just use multiple rotary switches per step in the sequence and not worry about ADC at all but it'd be nice to have a bunch of sliders and have tuning idiot-proof.
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Blue Hell
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PostPosted: Mon Nov 07, 2011 5:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

There is some PIC (processor) based quantizer thingie out there too ... after going AD you'll need DA too to make it analog again, that PIC thingie has both converters built in.

But yes you could do things on the source side too. Apart from a switch to select voltages you could also make coarse / fine controls to be able to tune it better.

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nullpainter



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PostPosted: Wed Nov 09, 2011 11:38 am    Post subject: Reply with quote  Mark this post and the followings unread

After further intimidation by data sheets and a bit of Googling (and wondering how others did it), I found this post about CV quantization so might try with the R/2R and a decimal counter.

It may not be the optimal approach, but sounds to be within my current comfort zone!
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fonik



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PostPosted: Wed Nov 09, 2011 2:55 pm    Post subject: Reply with quote  Mark this post and the followings unread

Blue Hell wrote:
But yes you could do things on the source side too. Apart from a switch to select voltages you could also make coarse / fine controls to be able to tune it better.

that's what i was thinking: either you do the quantizaton at the output of the whole sequencer (then i would recommend boogdish's simple quantizer - just search it here in the forum, i think he even sells a programmed PIC along with a PCB if you don't want to burn a PIC your own), or i would use a switch on each step instead of a potentiometer. the switch would select from a pre-set collection of voltages then (a resistor ladder with trimmers, maybe).

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patrickvf1976



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PostPosted: Wed Nov 09, 2011 4:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

I am very much a beginner in electronics, but I have a electronics lab and in one of the project books are instructions for a bargraph circuit. From the looks of it, it could be easily adapted for scaling notes as set by potentiometers. That seems to be IMO the simplest solution to your problem. Perhaps there's a similar circuit floating around on the web somewhere?
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Blue Hell
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PostPosted: Wed Nov 09, 2011 5:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Interesting idea patrick Cool

It may have some scaling issues, but its easy to mess around with and try.

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patrickvf1976



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PostPosted: Wed Nov 09, 2011 6:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

hmm perhaps replacing the LEDs with switching diodes (or switch ICs), followed by resistors should do the trick? No? Just an idea.. You don't have to make one circuit per pot, but just one for the whole row and have it switched from step to step (if that hasn't been considered already)
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