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Analog Sequencer

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Analog Sequencer

Postby toryjames » Wed May 02, 2007 11:49 pm

I am thinking about building a small 8-stage sequencer for my Moogerfoogers. It will be about the size of the CP, does anyone have experience with this? I have a schematic I got from an old book and it looks fairly straightforward: a 4017 chip (decade counter), 8 100k pots, 8 diodes, an 8-position switch, a 5-15V power supply and bunch of resistors. I'll post the results if I'm successful. Wish me luck.
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Postby latigid on » Thu May 03, 2007 3:22 am

Hey, I would love the schemo if that's possible.
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Postby electrical_engineer_gEEk » Thu May 03, 2007 11:05 am

Can i suggest building one of Ray Wilson's 16-step sequencers? He runs a website called Music From Outer Space that puts up open-source DIY info on synthesizers that are just absolutley amazing! Not only does he put the info out there but he also produces very very affordable bare PCBs that you just have to purchase the parts for. Not only that but he only uses easy to find ICs so you don't have to pay an arm and a leg for obsolete parts.
I have built his SoundLab synth and his website is just an amazing synth resource for the DIY community.
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Re: Analog Sequencer

Postby nathan » Thu May 03, 2007 5:38 pm

toryjames wrote:Wish me luck.


Good luck!

Sounds easier then the musicfromouterspace one. Let us know about it!
I would like to make one too!
:P
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Postby toryjames » Thu May 03, 2007 11:37 pm

Thanks for the 16-stage sequencer link, it's good to have cross reference stuff while I'm trying to figure this all out. It's good to see the commonalities and differences. Here's a page scan of the 10-stage sequencer (I'm going to probably make it eight by shorting out the last two outputs). It has no internal clock, I'm assuming it could be driven by the Moog CP square LFO. It's very bare bones but... here it is.
http://i6.photobucket.com/albums/y242/t ... encer2.jpg
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Postby nathan » Fri May 04, 2007 8:42 am

bleep. i never get these schematics. :( :oops:
i've made a mufffuzz and a tone/volume-thingy, that's it.
only from like drawn/simple schematics with no symbols.
i'm still looking for the book "electronics for dummies"
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Postby MC » Fri May 04, 2007 10:16 pm

electrical_engineer_gEEk wrote:He runs a website called Music From Outer Space


Nice web site

*files under favorites*
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Postby willi » Mon Jul 16, 2007 10:13 am

Any luck with this? It seems that the decade counter isn't hard to find. I'm a little confused though, is S1 supposed to switch between some other circuit in your book and an incoming LFO? What book is this from? And how about having all the outputs in a single jack, so you can drive a VCO frequency instead of (apparently) 10 different CV outputs?

Thanks
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Postby toryjames » Mon Jul 16, 2007 2:47 pm

willi,
Yes, it was a successful project. Here is a picture I just took next to some everyday objects to give you an idea how big it is. It is a bit smaller than a Fooger pedal which is what I was going for. I used 16mm pots instead of standard 24mm ones so they'd fit onto a smaller panel. I bought most of the supplies from www.mouser.com. The enclosure and knobs are from Radio Shack.

http://i6.photobucket.com/albums/y242/t ... CN5711.jpg

Yes, in the book ('Sound Synthesis' by Terence Thomas) there is a voltage controlled pulse generator project which would drive the sequencer's input. The schematic shows a switching jack where an external clock may be inserted. I decided to build the sequencer first and drive it with some of my other equipment (Paia Midi CV Converter). I was expecting to drive it with the LFO square wave from my Moog CP but it seems the signal was not strong enough. In the photo you can see that I left off the pulse output jacks (because I didn't have much use for them). I wanted to keep it as simple/small as possible. Yes, I think you could connect all of the pulses to a single jack, but it would be the same steady pulse that you have going into the sequencer. You could probably connect each stage pulse through its own switch, then to a single jack. This way you'd have control over which stages sent a pulse, creating a rhythmic pattern.
The sequencer is designed to output 0-15V, Fooger's inputs are 0-5V so you either just use the lower 1/3 of the knobs or run the CV output through a passive attenuator (a voltage divider: a 100k pot and two jacks, much less complex than it sounds) to knock the output voltage down to 0-5V. Now you can use the full range of the knobs without overloading the MF's CV inputs.

Note: There is an error on the schematic, the first stage potentiometer should connect to its corresponding diode just like the rest. Its 3rd lug should not connect to the center lug (when connected this way it shorts itself out, causing stage 1 to remain at minimum [0V] regardless of its panel setting).

Overall, it was pretty simple. It was my first project built from scratch and it actually works, I wasn't really expecting that. I'm sure I could be clearer on some of these points, so if you have any more questions please ask. It should cost you around $50-60 for parts (potentiometers being the biggest expense, I used Linear (you don't want audio taper) 100K 16mm Alpha pots from Mouser). Good Luck, let me know how it goes.
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Postby toryjames » Mon Jul 16, 2007 3:08 pm

Duh. This picture is more appropriate. I don't know why I thought coins and a pencil made sense.

http://i6.photobucket.com/albums/y242/t ... CN5712.jpg
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Postby Bryan T » Mon Jul 16, 2007 4:57 pm

Very cool project! What is the range of tempos? The next step is to add a tap tempo circuit.

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Postby toryjames » Mon Jul 16, 2007 10:03 pm

Thanks. The large knob is actually a 10-position switch which selects the number of stages in the sequence. The tempo is determined by an external pulse applied to the first 1/8" phone jack. I have a Paia Midi-CV Converter that I use to drive the sequencer's input. It becomes less of a stand-alone device without it's own internal clock, but using an external MIDI clock it will stay in time with other sequencers or Cubase on my laptop.
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Postby willi » Tue Jul 24, 2007 10:08 pm

Thanks for the info, your project seems to have turned out quite well indeed bosshog. The photos are great, too. After looking closely I see the error on the schematic that you mentioned. If you follow that section of the circuit straight up, you'll see the part which then connects to pin 3 of IC1 does not also go up to the big rotary switch section labeled Stages like the rest of the other Pot/Diode/IC1 circuits do. Is this also an error? I don't understand why the first section would be left off the rotary switch. Also, when you left off the individual pulse output jacks, did you only remove the jack, or the resistor as well?

Can you post a pic of the pulse generator circuit that is supposed to go with it?

Thanks!
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Postby toryjames » Thu Jul 26, 2007 6:21 pm

Those upper connections are for resetting the sequencer to Stage 1. They connect to the switch so the user can determine the number stages for the sequence. Visually it appears it might be an error, but I don't believe it is. Pin 3 sends a pulse at Stage 1, at this setting the sequencer would reset itself at the first stage. This would cause the sequencer to remain at stage one (not very useful). As it is designed, two stages is the minimum length (acting like a square wave LFO) with a maximum of 10 stages.
Yes, if you omit the individual pulse output jacks (the vertical row along the right of the schematic) you can leave off the resistors as well.
I'm away from home but I will post the pulse generator schematic as soon as I return. I'll probably post a higher resolution copy of the 10-Stage Sequencer as well.
Unrelated but somewhat exciting, today I found a copy of Allen Strange's "Electronic Music: Systems, Techniques..." for $1.50 at the Laguna Beach Library book sale!!
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Postby willi » Tue Jul 31, 2007 12:16 pm

Ah, thanks for the explanation. The large rotary switch definitely makes more sense now. If you get a chance to post the pulse generator schematic, that would be great. I'm still intrigued by the switchable 'pulse rhthym' concept you mentioned. Can someone share a few examples of where this might be useful? Perhaps it would be nice to route this CV through a lag processor for some applications?

If it ends up seeming useful, I might redraw the schematic (in my spare time, haha) to include the sequencer, pulse generator, and the switchable 'pulse rhthym'. I would probably also consider connecting the summed pulse rhthym output to a mult. :D
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