MK107 sequencer

[ohnoitshoward]

thank you for the wonderful clear instructions. many thanks!

[MirlitronOne]

Why not? For portability. Convenience. And to avoid encouraging some of the visitors here to blow it up or to electrocute themselves.

[KorgAddict1]

Really cool! I'm curious as to why you decided to keep the circuit running on a 9v battery instead of replacing it with a 9v universal power supply?

[robman80808]

Thanks for posting this. Going to give it a go (newbie). Could you please answer a couple of questions for me to avoid toasting my Monotron? 1. Is the gate out wired without a ground? It looks like there is only one wire in the video. 2. What resistors did you use to ensure only a 5v max output? 3. I'm new to diodes - Maplin has a Schottky Rectifier Diode. Is that the one I need? If not, is there another product at Maplin I could use (no AO91 on there).

Many many thanks!

Rob

[MirlitronOne]

You wouldn't want the rate to go down to 0 bpm though, or all the action will be in the last few degrees of the pot. 60 - 280 is more reasonable.

Sorry, I don't have a reference for the Bongotnik circuit. All I can tell you is that it was based on "The Audio Artist Sound Effects Machine" by James Barbarello, published in Popular Electronics in the mid 1970s - early 1980s. Maybe there are indexes online where you can track it down.

[MirlitronOne]

Granoj1's comment was copied to me and didn't seem like spam, so here goes: the components that determine the clock rate are C3 (the 1 uF capacitor) and the variable resistor. You can limit the lowest and highest rates with resistors either side of it. R10 already limits the highest rate in the original circuit. The clock is a 555 timer, so the 555 data sheet or any good electronics primer will tell you how the frequency depends on the resistor and capacitor values.

[granoj1]

Clever thinking! Is there any way of limiting the rate of the sequencer? What I`m after is getting the sequencer to a more musical range something like 0-280 bpm. I dont`t really care about noise as plain noise but when it`s rhythmic things get interesting. By limiting the range you would also get more precise control over the sequencer I think. Also, I love your Bongotnik but the link to Synthdiy article is dead. Could you advice me where to find the schematic? Thanks!

[MirlitronOne]

No - the 4015 chip has no reset line.

[scttcmpbll]

can this be set up to be less than 8 steps like a 4017?

[MirlitronOne]

No, I'm secretly MirlitronOne. Ooops.

[JingleJoe]

Are you secretly thunderfoot?

[MirlitronOne]

Yep, that's all you need. The only addition to mine was a switch and limiting resistors to ensure that the output does not exceed any input limits on the circuitry to which it is attached. Normally, this won't be a problem, especially if you are careful not to turn the output (range) pot higher than is needed to give you the pitch range required.

[cpkcpk1]

Looks great! Please could you list the components to get besides the MK107 kit to make one identical to yours? So far I've got:

-8 10kOhm linear potentiometers

-100kOhm linear potentiometer

-8 diodes

[MirlitronOne]

Yep, shouldn't be any problem with that. Which MFOS synth are you building?

[heytreacle]

@MirlitronOne Great stuff- I'm building the "Mini-Synth" version, the slightly less complicated one. Probably only a day away from testing it out. By FAR the most complicated project I've undertaken but have gone a little bit OCD on checking and re-checking everything as it goes in so... famous last words eh?

Will attempt your idea of sending the output beyond hearing frequency to turn "off" steps on the sequencer and will post a vid I think if it comes together. Once again, great idea, thanks:)

[MirlitronOne]

It's a sequencer. It outputs a repeating sequence of discrete voltage levels that can be used to drive a voltage-controlled oscillator which then generates the tone.

You need a VCO for it to drive. There are loads of simple designs out on the web - using CMOS ICs or a 555 timer, for example. It doesn't have to be high quality - it doesn't matter, for example, if it's linear or exponential voltage response, or nothing in particular, whether higher voltage give higher frequency or vice-versa.

[heytreacle]

@MirlitronOne Thank you for the reply, that makes sense- so far I've just been building basic guitar pedals and thus vagaries of old synth set-ups escapes me.

I'm half way through a MFOS Mini-Synth- I guess I'll be able to feed it directly into one of the two CV Oscillators?

[heytreacle]

What an ingenious bit of left field thinking. Thanks for sharing.

I've got one on the breadboard now- a built circuit board with leads from chip/resister point running out to the diodes and pots for testing.

I'm only getting a 'click' out of the circuit to my amp though, I can adjust the 10k pots and hear a slightly lower or higher pitched click... but no actual beep or tone.

Am puzzled :(

[MirlitronOne]

Please read previous answer, and listen carefully to the video.

[DornerKevin]

could you make the schematics

[MirlitronOne]

I don't have time. If somebody else who understands the circuit would like to do so, I give them my blessing. Meanwhile, if you teach yourself enough electronics to be able to do this yourself, you will find it all worthwhile.

[kasta867]

why you don't make written instructions (like on instructables)?

I really want build one of this!

[cameron5235]

Brilliant! Thanks for coming up with this. I've got one of those kits lying around somewhere, and I really want to build a CV sequencer. Wish I'd thought of it!

[MirlitronOne]

Good! Please let us see it when it's done!

[SkunkyMonky420]

Is the diode type OA91 suitable for this project?

[MirlitronOne]

Yes, the OA91 is ideal.

[SkunkyMonky420]

@MirlitronOne

Brilliant thanks for the advice, Im hoping to build this circuit into an enclosure with a middified gakken sx-150 circuit and an analogue delay circuit, Should be a fun journey.

[MirlitronOne]

Great, let's see it when it's done! That'll be a nice machine when it's complete.

[rockangel1967]

i had the same idea a few months ago and have built a similar system, using this maplin kit. as oscillator i used a 4093 but had to put a LM337 transistor between to create enough power. the 4093 or even better the 40106 produce a real nice sound

cheers

[MirlitronOne]

Thanks for the information. I have certainly had problems using an external clock for this gadget, and yes, a transistor buffer stage helps a lot.

[rockangel1967]

@rockangel1967 what you can do as well is to trigger some 4066 switches with the sequencer. using 4093 oscillators again but these are oscillating nonstop, with the 4066 you just let the output thru or not. this would be the "cleanest" way to do and you wont have voltage dropings on the 4093 which can sound weird. i am using 47nF or 0.01uF axial polyprob capacitors which sound best in my opinion. (stock nr: 114-474 at RS components uk) see my video. there is a 8 step sequencer. :-)

[acidjack303]

Verry Nice one. i ve build it after watching your video. im just a beginner and i learnd a lot.

Thanks for this.

I have a small question and hope if you can give me a info.

Some one told me that you can add some switches to switch of some notes.

where is the best place to conect them. will nice if you can give me a tip !

thanks,

thorsten

[MirlitronOne]

No, you cannot easily switch off notes with this simple device, since you cannot program it to produce silence, nor can you easily block the trigger pulse. Normally, it would just produce either the lowest or highest note if you reduced the output to zero volts.

One possible simple workaround would be to have notes that are either sub- or supersonic, so that they are 'played' but cannot be heard.

[yopdiesel80]

Thanks for the video ! I have just built one and it works great with my Gakken SX-150. Instead of using a 100K pot to control the voltage output, i used a 1M linear pot, works like a charm !

[MirlitronOne]

Glad to hear it! As long as the output pot has about 10x higher value than the individual level pots (or more), all should be fine. Have fun!

Another cheapy Velleman project is currently under development that should interest the synth community...

[acidjack303]

Verry Nice one. i ve build it after watching your video. im just a beginner and i learnd a lot.

Thanks for this.

I have a small question and hope if you can give me a info.

Some one told me that you can add some switches to switch of some notes.

where is the best place to conect them. will nice if you can give me a tip !

thanks,

thorsten

[lesserepiphanies]

Thanks for the note.

I've tried to see if you have a website, ideally with schematics or building notes. You're kind of elusive! But I will keep my eyes open.

Best wishes for this, and all your endeavours.

e.

[MirlitronOne]

No time to maintain websites! The schematic comes with the kit, although there are various sites that publish the Velleman schematics - they don't keep them secret. The building notes are the video, although the 'Baby 10' sequencer article (use Google) will help too.

I'm working on another Velleman kit-based design, too - watch this space.

[lesserepiphanies]

This is brilliant.

[MirlitronOne]

Thank you most kindly! My most recent mod is to replace the 555 timing capacitor with one 5x bigger to allow slower sequences. Enjoy.

[alecjahn]

Fantastic run-down on the project. It's definitely the perfect little platform for this sort of project.

cheers!

[MirlitronOne]

Happy to oblige! A number of builders have come back to me with positive comments and it's been great to hear from them.

[swishpan]

Great and thanks a lot. I'm trying to sequence the gakken 150 but it takes only AC vco so have to maybe use a sine generator in between.

[MirlitronOne]

Waaaah? How on earth does an AC control voltage work? It seems completely contrary to common sense!

[swishpan]

The only way i could get the external input to work was with audio signal at high level or sine/sqare wave. Works just like DC. Higher voltage - higher pitch. But the gakken can take normal VC between ground and the stylus pin.

[PHANTOMPOWERS]

Nice one! I'll be making one as soon as I get the bits.

[lazymandoplayer]

Nice ideas - thanks

[nondirectional]

Excellent work, I've been trawling around trying to find a way to build some sequencers on the cheap, and this looks and sounds like the ticket! And less messy than the baby 10 style I built recently. Any close up pics available? Keep up the good work,

[MirlitronOne]

I've tried taking some close-up shots but I haven't managed to get any that really show the necessary connections. If you're familiar with the Baby 10 circuit, you'll find this easy enough - just bear in mind that this circuit is limited to eight-note sequences - you can't have shorter sequences like you can with the 4017.

[nondirectional]

I'm thinking of buying four of these kits, and using one of the rate pots to control them to keep in sync, then sending off each CV to other synths. I wonder if a simple on/off switch can be applied to each step?, or maybe not for this circuit type?

[MirlitronOne]

What you want to do is not as simple as you describe. First, you will have to disable the 555 clocks to three of the boards (this is easy, just leave out the 555 chips) and then route the output from pin 3 of the remaining 555 to the pin 3 location on the other three boards.

[MirlitronOne]

Omitting steps is much more difficult. Using switches just means that each 'off' step will produce something near zero volts at the output. Depending on your VCO, this will almost certainly produce either the lowest or highest note from the VCO. In order to produce silence usually requires gating the VCO output in some way. This can be done with 4066 switches but will add enormously to the complexity.

[g0shu4]

GENIUS!!!

[SonofCastille]

GOOD SHOW,OLD BOY!thanks for posting.

[MirlitronOne]

Thank you, kind sir. Appreciated.