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-minus-
Joined: Oct 26, 2008 Posts: 787
Audio files: 13
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Posted: Wed May 01, 2013 6:56 pm Post subject:
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Oh good! yes it seems obvious now if you look at your test results above. Pin 3 should read 0V, the same as pin 6. Glad it's working for you . |
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jackdamery
Joined: Apr 26, 2010 Posts: 75 Location: UK
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Posted: Thu May 02, 2013 6:22 am Post subject:
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nicolas3141 wrote: |
If you want to convert it to vague V/Octave response (ie not accurate and not worth wasting tempcos on) then the simple V/Oct converters that are often used on the front of VCF circuits could be adapted to this. I haven't tried, but it probably wouldn't be too hard. One or two op-amps and one or two transistors would be all it would require. |
Could you give an example schematic of an expo convertor that might work? |
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analog_backlash
Joined: Sep 04, 2012 Posts: 393 Location: Aldershot, UK
Audio files: 21
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jackdamery
Joined: Apr 26, 2010 Posts: 75 Location: UK
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Posted: Thu May 02, 2013 3:25 pm Post subject:
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Thanks for your help Gary. Today I added a simple expo convertor with a PNP/NPN pair(as per Synthmonger's schematic) and got it tracking 1V/Octave over about 3 octaves reasonably well. Then obviously I connected it to the Arduino MIDI2CV and made it play the bassline to Blue Monday by New Order. Here's the irritating thing though, there is a 300ms delay between hitting the note on the keyboard and the frequency changing, I'm pretty sure it's the expo convertor.
https://soundcloud.com/dot/lm358-vco-blue-monday-bass |
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jackdamery
Joined: Apr 26, 2010 Posts: 75 Location: UK
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Posted: Thu May 02, 2013 3:27 pm Post subject:
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If anyone wants to the know, the transistors I used were BC337 and BC338. |
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analog_backlash
Joined: Sep 04, 2012 Posts: 393 Location: Aldershot, UK
Audio files: 21
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Posted: Thu May 02, 2013 4:03 pm Post subject:
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Hi (again).
Glad that you got it working and for such a lo-fi circuit, that sounds pretty good! I'm a bit puzzled by the 300ms delay, as I wouldn't expect that circuit to introduce much delay at all (but I'll probably be proved wrong...). I wonder if you'd still have the same problem with the better op-amp plus transistors circuit?
Good luck
Gary |
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jackdamery
Joined: Apr 26, 2010 Posts: 75 Location: UK
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Posted: Thu May 02, 2013 4:20 pm Post subject:
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Hi I don't know what the delay was, but it suddenly stopped doing that. Is there any resistors or pots I could change to scale this better over more octaves? It sounds very good in the bass octaves but I'd like the slightly higher ones for sweet pads. Maybe the C1 could be changed for a smaller(if possible?) value to get a higher fundamental frequency? |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
Audio files: 18
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elmegil
Joined: Mar 20, 2012 Posts: 2177 Location: Chicago
Audio files: 16
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Posted: Thu Jun 06, 2013 11:35 am Post subject:
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It's a pretty standard Expo converter.
However, I don't think it will do what you want. This VCO is driven by V/Hz, to use it with other equipment you need something that takes V/Oct in and outputs V/Hz. |
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tupinamba
Joined: May 14, 2010 Posts: 24 Location: France
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Posted: Tue Jul 02, 2013 2:58 am Post subject:
Wow! |
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I just built this circuit to add a VCO to my Korg MS-10 and it is working great! I first had a problem as it wouldn't stay tuned (an octave on the keyboard resulted in about 9 to 10 semitones on the VCO), but this was because I was using a single 9V battery with a virtual ground. I switched to a pair of 9V and now it is great!
Just one thing I don't get... inlifeindeath, you said :
inlifeindeath wrote: | it already has a freq pot. two pots are shown; one can be wired as a CV attenuator and the other one can just be hard wired to V+ on the CV end and you have a freq pot. |
But I'm not sure what is "CV end" where I should connect the second pot...
Thanks Nicolas and thanks Chris, as it is your video that made me try this circuit! |
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inlifeindeath
Joined: Apr 02, 2010 Posts: 316 Location: Albuquerque, NM
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Posted: Tue Jul 02, 2013 12:12 pm Post subject:
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CV end meaning the side of the pot on the schematic where CV In is indicated. Rather than having CV on that end of the pot, just wire it to +V for a frequency control. _________________ http://www.youtube.com/user/borisandfef |
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tupinamba
Joined: May 14, 2010 Posts: 24 Location: France
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Posted: Wed Jul 03, 2013 7:16 am Post subject:
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Alright, thank you inlifeindeath!
About the CD40106 schmitt trigger inverter, do I simply need to connect V+ to VDD pin (14), 0V to Vss pin (7) and saw output o one of the inputs? Is this as simple as that to get a squareware form?
Thanks! |
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tupinamba
Joined: May 14, 2010 Posts: 24 Location: France
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Posted: Sun Jul 07, 2013 2:22 am Post subject:
Building a more stable v/hz VCO ? |
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Hi again,
I'll still pretty astonished by the results I got with this basic VCO ; I built a +-12V PSU for it and I'm working on a nice little enclosure that will nicely get on top of my MS-10.
I'd like now to go one step further and built a more stable v/hz VCO for my MS-10. But the schematics (and boards, as I'm not very good at translating a schematic into a PCB...) are mostly v/oct.
Is there a not too complicated but still efficient and stable DIY v/hz VCO out there?
Thanks in advance! |
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david.tb303
Joined: Oct 05, 2012 Posts: 5 Location: barcelona
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Posted: Sat Sep 21, 2013 12:18 am Post subject:
add fine tune to this VCO |
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hi! i build this VCO and works fine ( thnks Nicolas for your designs, pretty simple for a newbie as I'm! ).
But now i would like to add a second potentiometer to allow fine tune the frequency, because the range playing now is so big. This is very nice but if doesn't very dificult i like to know how to connect this VR.
Thanks in advance |
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jackdamery
Joined: Apr 26, 2010 Posts: 75 Location: UK
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Posted: Sun Sep 22, 2013 4:27 pm Post subject:
Re: add fine tune to this VCO |
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david.tb303 wrote: | hi! i build this VCO and works fine ( thnks Nicolas for your designs, pretty simple for a newbie as I'm! ).
But now i would like to add a second potentiometer to allow fine tune the frequency, because the range playing now is so big. This is very nice but if doesn't very dificult i like to know how to connect this VR.
Thanks in advance |
Hi david,
Try adding a 100k potentiometer, with one end connected to +9v and the other to -9v then connect the wiper (middle leg) to one end of a 1M resistor then the other to the inverting input (-) of IC1A.
Basically you have a resistor (your pot) between your supply voltages and your wiper is the potential divider between those two. So you can sweep the wipers output between 9v and -9v by adjusting the pot. The 1M resistor will limit how much of this can get to your oscillator to a very small amount though thus affecting the frequency only a little, giving you fine tuning.
Try between 1M and 3M by adding resistors in series until you find a range of fine tuning that suits you. A standard one might be to try to get 1 semitone of adjustment from one end of your potentiometer to the other. giving you 50 cents each way, this is the range of fine tune on the VCO2 of the Jupiter 8. |
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david.tb303
Joined: Oct 05, 2012 Posts: 5 Location: barcelona
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Posted: Sun Sep 22, 2013 10:45 pm Post subject:
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thank you very much jackdamery! Many thanks, not only for the answer, but the explanation which I think helped me to understand |
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jackdamery
Joined: Apr 26, 2010 Posts: 75 Location: UK
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Posted: Mon Sep 23, 2013 12:02 am Post subject:
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david.tb303 wrote: | thank you very much jackdamery! Many thanks, not only for the answer, but the explanation which I think helped me to understand |
No worries, here's the same thing applied in Thomas Henry's VCO1. The first opamp is acting as a DC signal mixer that you feed all your control voltages to. It combines them and then the sum of them determines the gain of the opamp.
If you remember with an inverting opamp gain is the sum of your feedback resistor divided by your input resistor you can work out what the gain will be for each part. http://lambertsound.com/forums.html?pr=Op-Amp_Basics.
A higher input resistor (1M) will equal a smaller gain, thus making a smaller difference to the sum of your control voltage.
http://www.birthofasynth.com/Thomas_Henry/pdf/VCO-1/vco1_schem1.pdf
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Ruebezahl
Joined: Mar 09, 2014 Posts: 104 Location: Taiwan
Audio files: 4
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Posted: Sun Mar 09, 2014 8:23 pm Post subject:
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Hello. First thank you for the noble work to design these kind of simple, understandable circuits. I am a Beginner, and those circuits are very helpful. I would like to integrate this vco in a chain of some other small devices. in the end its planned to be something like a little sequencer feeding a square wave (4046) and sawtooth vco used interchangeable (that would be this one here), afterwards filtered through a LP-Filter (i used a schematic from mfos).
well, but now all the other parts running from a single 9V Battery. Although i finally understood the concept of this "Dual Power Supply", or whatever is the proper name for that, i am still not sure what exactly is the advantage of that.
Could you build a similar circuit powered by a single 9V, or is it something completely different? Because since all the other parts are working that way, i am tempted to build the whole device on one battery. But i guess there is a good reason for this "special" power supply.
So i hope someone can bring some order in my confusion, maybe even a link, providing me with some basic information on this sort of power supply and what are the advantages of it, could help me already a lot.
Thank you! |
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nicolas3141
Joined: May 25, 2007 Posts: 185 Location: Christchurch, New Zealand
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Posted: Sun Mar 09, 2014 8:38 pm Post subject:
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Yes this design runs fine from a single 9v battery. You just need to create a midpoint voltage to use as the 0V reference. See the latest circuit i just posted the other day that does this using a spare opamp. Or you could do it with a couple of resistors and caps. This is a very common approach in the stompbox world.
Nicolas |
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Ruebezahl
Joined: Mar 09, 2014 Posts: 104 Location: Taiwan
Audio files: 4
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Posted: Sun Mar 09, 2014 9:07 pm Post subject:
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Wow thank you for the super fast reply. And good news as well . So i will try it out as soon as i am back home.
But since i also want to learn and grow, and since a lot of your circuits use this special power supply, what is the advantage of having this 0V Ground instead of having just +9V and +9V (wich also works as a ground)? Because thats the way i actually learned it a few months before (in the book of nicolas collins). if you don't feel like going deep in that topic maybe you could give me a name for this method, so i could google it and find informations myself. |
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Ruebezahl
Joined: Mar 09, 2014 Posts: 104 Location: Taiwan
Audio files: 4
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Posted: Mon Mar 10, 2014 8:13 am Post subject:
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Just to make it sure: The circuit you are talking about is this one right? http://electro-music.com/forum/phpbb-files/bleeper_250.jpg
And the part in it, wich operates as the midpoint-voltage-generator, is the circuit in the middle of the sketch right? the one working with IC1 and IC2 op-amps. |
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nicolas3141
Joined: May 25, 2007 Posts: 185 Location: Christchurch, New Zealand
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-minus-
Joined: Oct 26, 2008 Posts: 787
Audio files: 13
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Posted: Wed Mar 12, 2014 2:21 pm Post subject:
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This is handy information nicolas. Could you explain what the IN is about in figure 3? Thanks. |
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nicolas3141
Joined: May 25, 2007 Posts: 185 Location: Christchurch, New Zealand
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Posted: Wed Mar 12, 2014 2:32 pm Post subject:
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In fig 3 i am just trying to show some generic amplifiers as examples, in and out are the signal in and out connections for inverting amps. Not really anything to do with the current discussion. Sorry for the confusion.
Nicolas |
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cablebasher
Joined: Mar 18, 2014 Posts: 3 Location: london
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Posted: Tue Mar 18, 2014 2:16 am Post subject:
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Hey dudes,
Is anyone able to upload any photos of this curicuit on breadboard or perfboard as a reference?
Not that great at following schematics.
Thanks. |
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