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 Forum index » DIY Hardware and Software » The layout factory
basic volt per octave keyboard schematics
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Cfish



Joined: Feb 24, 2016
Posts: 477
Location: Indiana

PostPosted: Wed Nov 09, 2016 2:58 am    Post subject: Reply with quote  Mark this post and the followings unread

13 dollars US on eBay. Took about 4 weeks to deliver from china. Mine is 15v+-
They have them in 12v+-

That one is running MIDI toCV, VCO, Divider Module, sequencer, mixer, LFO, 2 EGs, 2 VCAs, Noise generator, VCF. Not sure of the milliamp draw. But it does not heat up at all.


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alanwilder81



Joined: Sep 03, 2016
Posts: 310
Location: italy

PostPosted: Wed Nov 09, 2016 11:45 am    Post subject: Reply with quote  Mark this post and the followings unread

hey Grumble Smile
i know you went mostly digital eheheh
as for switch power supply to avoid, what exactly are they? Embarassed Embarassed
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alanwilder81



Joined: Sep 03, 2016
Posts: 310
Location: italy

PostPosted: Wed Nov 09, 2016 11:56 am    Post subject: Reply with quote  Mark this post and the followings unread

hey Cfish

i am really glad you found this circuit to be useful !

i am yet to find time to set it up and give it a go.
According to Yves Usson it works flawlessly. A french friend of him , specifically a teacher, tested it before publishing so it should be alright!

its a type of circuit very hard to find on the net, i mean the old school way of generating CV GATE TRIGGER by the means of a fully analog circuitry and a resistor chain. so i was very happy to find it and share with you and other mates looking for the same basic keyboard controller.

as for the power supply ,i might consider buying a kit like yours. cheapo ! Cool
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Grumble



Joined: Nov 23, 2015
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PostPosted: Thu Nov 10, 2016 1:35 am    Post subject: Reply with quote  Mark this post and the followings unread

alanwilder81 wrote:
hey Grumble Smile
i know you went mostly digital eheheh
as for switch power supply to avoid, what exactly are they? Embarassed Embarassed

Very basic: a switched power supply uses a technique where small portions of the mains voltage is used to charge a capacitor (your average iPhone and Android charger)
So you could imagine the noise this type of power supply creates...
A linear power supply uses a mains transformer and produce far less noise (mainly hum...)

Read more HERE
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alanwilder81



Joined: Sep 03, 2016
Posts: 310
Location: italy

PostPosted: Thu Nov 10, 2016 4:25 am    Post subject: Reply with quote  Mark this post and the followings unread

interesting matter Grumble.
so far i've focused only on studying EE basics, reading schematics ,building the various modules but never ever payed much attention to the power supply whole thing.

Sooner or later i'll have to get one Smile
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alanwilder81



Joined: Sep 03, 2016
Posts: 310
Location: italy

PostPosted: Fri Nov 11, 2016 3:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

hey Cfish,
i just posted a new message, but i cant find it, so i'll post it again
i finally managed to breadboard the CV GATE TRIGGER circuit we've been talking about.
It does work,although some tweaking may be needed.I'll now describe fast the procedure.
I used a CD4016 in place of the CD4066 the schematics calls for.I also used the TL084 instead of the TL074,That aside,no other modification took place.
Used 47 ohm resistor chain,one percent tollerance or better. for most of them i had a reading of 46.8 ohm or thereabouts. So,reasonably matched.

I got a CV output span from 1.1 V to 4.05 V, adjustable with the 10 K trimmer. The gate was around 11.6 V. Close to the values the schematics referres to.
I hope i got t right.How about yours? Smile
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Cfish



Joined: Feb 24, 2016
Posts: 477
Location: Indiana

PostPosted: Fri Nov 11, 2016 5:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Alanwilder81
Mine is working well. I'm running on 15v+- and using 100 ohm resistor chain. It has not taken a lot to make it work for my system. I am working with the top section and sample and hold section at the moment. Am really looking forward to the final gate and trigger circuits. I'm unfermilior with how the trigger is functioning. I hope I can understand it when I'm done.

I intend on using this circuit in the keyboard I roughed together today. The top deck is the circuit I had worked with for a while, it has no trigger. Didn't realize how much I wanted trigger untill things progressed.

Figured if I roughed the case together, it might get me motivated to finish this project up.


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alanwilder81



Joined: Sep 03, 2016
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Location: italy

PostPosted: Sat Nov 12, 2016 1:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

hey Cfish Smile Smile

congratulation on the keyboards and especially the the bottom one bare wood.I think it looks awesome! Are you a carpenter if i may ask?

I also plan to build myself a case like that.Or even a small cabinet,dont know yet. i am still struggling with the electronics.
My keyboard circuit, as i said, outputs both GATE and TRIGGER as well as CV to drive the VCO's. Trouble is, i dont have the CMOS 7555 to build my VCO to test the keyb circuit rigth away. Only have ne555's at hand , but they are totally worthless for that matter.
as far as your setup, how do VCO's responde to the CV output? you able to get proper frequencies and scales? Did it take you some trimming?

i now have my circuit sitting on the bench ready to be tested with a vco, i may be better ordering next week the missing component to realize it
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Cfish



Joined: Feb 24, 2016
Posts: 477
Location: Indiana

PostPosted: Sat Nov 12, 2016 7:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi alanwilder81

Here is a video link. Still have a small problem with my sample and hold circuit. It shows in the video. I have everything adjusted pretty well.

https://youtu.be/aR4tU0q65DA

If you happen to have access to a 2n2646 UJT, you could build this quick VCO to test things with. It only tunes correct for a little over 2 octaves. It's what I use in the bass pedals in the video


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alanwilder81



Joined: Sep 03, 2016
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PostPosted: Sun Nov 13, 2016 6:25 am    Post subject: Reply with quote  Mark this post and the followings unread

hey cfish,
that sounds really fat and thick Shocked Shocked Cool Cool Very Happy Very Happy .just analog beauty. the sample and hold issue you refer to is about your self made circuit project, or the yusynth one you just built ?
to me,the Yves Usson SH works pretty well, at least my DMM reads a even voltage. as for the VCO you posted looks simple enough to give it a go for a quick and dirty test !
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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Sun Nov 13, 2016 6:30 am    Post subject: Reply with quote  Mark this post and the followings unread

great thread guys! thumleft Hail the Master
someday I will built myself a volt-per-octave-keyboard and this is going to be very useful.
for now I just sit at the back of the classroom and take notes.

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alanwilder81



Joined: Sep 03, 2016
Posts: 310
Location: italy

PostPosted: Sun Nov 13, 2016 7:07 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks phobos for the support ! Wink Wink thats really sweet

we embarked on a hugely complex project i reckon ,we need some means of controlling the vco's ,just like a keyboard!!
i havent seen much on the net regarding pure analog keyboard circuits. So as soon as i found the schematics i posted i decided to share with you chaps, also to get all the help is needed to wrap my head around this mess.
it's stuff well over my head Crying or Very sad Crying or Very sad not having a formal EE education, but passion, perseverance, studying and swapping info on this forum can make up for it.
What are you phobos up to? ive seen many of your projects floating around ! let us know ! Cool
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Cfish



Joined: Feb 24, 2016
Posts: 477
Location: Indiana

PostPosted: Sun Nov 13, 2016 9:18 am    Post subject: Reply with quote  Mark this post and the followings unread

To alanwilder81. Yes that is my circuit I had been working on in the video. Not the yusynth circuit.

Not really my circuit. Started out with an old EFM circuit that I could never make work. However the initial opamp with the resistor chain in the feedback loop seemed to track CV really well. So I just kept trying to build on it.

I will note that the bass pedals in the video are passing the VCO through a passive low pass filter. And a PT2399 delay circuit. There is a thread about that project on here. Think it's titled easy analog synth project.

2n2646 UJTs are available on eBay in the US. Normally come from the U.K. Not sure why that is.

I do have several extras if someone needs a couple. PM me


PhoBoS. I would love to see what you come up with on the volt per octave keyboard project. I have learned so much from your threads. Thank you so much for being here.
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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Sun Nov 13, 2016 10:09 am    Post subject: Reply with quote  Mark this post and the followings unread

alanwilder81 wrote:
not having a formal EE education, but passion, perseverance, studying and swapping info on this forum can make up for it.
It is pretty much the same for me although I do have somewhat of an EE education. But I never finished it and honestly hardly learned anything
from it. Before I had internet access I learned mostly from studying schematics published in Elektuur (elektor magazine) and when I finally got
online a whole new world opened and it became a lot easier to find information. Of course this forum has been a huge help and inspiration.

As usual I am currently working on a couple of projects but my Scraprack has the highest priority as it will save me some space and makes it
possible to connect more stuff together.


Quote:
PhoBoS. I would love to see what you come up with on the volt per octave keyboard project. I have learned so much from your threads. Thank you so much for being here.
aw you are too kind Razz I am learning things from you as well and you're as much a part of the EM community as I am!

If I would make a volt-per-octave keyboard it would probably not be very different than what I see here. Unless you go digital there aren't many
options and you will quickly end up with a resistor string and a temperature stable buffer/converter. A comparator for a trigger/gate output is of
course very useful and you can expand with a S&H and glide.

hmm, I just realized a S&H might or at least could be used here for stability, I guess I have to read back a bit.

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alanwilder81



Joined: Sep 03, 2016
Posts: 310
Location: italy

PostPosted: Sun Nov 13, 2016 10:17 am    Post subject: Reply with quote  Mark this post and the followings unread

to phobos,

yes, the net opened up a whole new world to anyone.Before that, you could only rely on magazines,manuals and stuff lke that.
Nowadays even a complete noob like myself can have access to goldmines like this forum and therefore be able to build himself the hell out of synth modules Smile.And the willing member are always there to lend a hand or share some knowledge.Priceless !!
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alanwilder81



Joined: Sep 03, 2016
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Location: italy

PostPosted: Sun Nov 13, 2016 10:21 am    Post subject: Reply with quote  Mark this post and the followings unread

phobos,
anyway stay tuned. Cfish and I have been working on the above project, so, i hope some nice resoults will come soon
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alanwilder81



Joined: Sep 03, 2016
Posts: 310
Location: italy

PostPosted: Tue Nov 15, 2016 2:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

hey chaps

that might be a bit off topic, but being in search for a basic 1 V oct VCO to test the keyboard circuit, i came across this wonderful article.

http://www.allaboutcircuits.com/projects/diy-synth-series-vco/

This VCO calls for a LM358. Which i dont have.
Can it be replaced by any TL xx op amp series?
It's connected as a comparator i believe. i have also LM 393 at hand.
Are those to be considered valid replacements ?
the keyboard circuit is completed and cant wait to test on a reliable VCO ! Smile


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Cfish



Joined: Feb 24, 2016
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Location: Indiana

PostPosted: Tue Nov 15, 2016 3:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Alamwilder81

LM358 is a single supply opamp ( power to ground not -v) I don't see a reason TL07xx won't work at a glance. As long as you tie -v to -v not ground

+ inputs on TL07xx still tie to ground. Ground being half reference voltage in +-12v which I think you are using
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alanwilder81



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PostPosted: Tue Nov 15, 2016 3:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks Cfish,

i'll give a solid TL074 a try. They are my workhorse and are cheap.By the way, what's your faved op amp? Smile
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PHOBoS



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PostPosted: Tue Nov 15, 2016 4:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

LM358 works just as well with a dual supply. I am actually not sure what the main difference is but I think it has some sort of internal
biasing. It's output can also swing closer to the power rails (especially the negative/GND one). Also, the TL072 has J-FET inputs and
therefor a much higher input impedance. So for example a S&H would work better with a TL072 than an LM358.

I personally have a soft spot for the uA741, because the first couple of opamp circuits I build used that one. But I rarely use it nowadays.

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Cfish



Joined: Feb 24, 2016
Posts: 477
Location: Indiana

PostPosted: Tue Nov 15, 2016 4:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

I also have a ua741 soft spot, for the same reasons. I tend to use 741 and Tl071 the most. My Thomas Henrey VCO1, I built with 071s on a 5x7 perfboard, so I had plenty of room to get in with the meater and scope and really figure it out.

One of the best moves I ever made.

Second VCO1 I built with 074. Fits in 1/4th the space on perf
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alanwilder81



Joined: Sep 03, 2016
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PostPosted: Tue Nov 15, 2016 5:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

lol Very Happy Very Happy

I cant wait to get the LM13700 and 7555 to start building the crap out of the Thomas Henry VCO's .Those projects are wonderfully laid out, easy to understand and so clear, schematic wise. And sound remarkably good.

Those VCO's will be the crowning achievement of my DIY project Razz Razz they are in store.
As for the opamps, i am a green horn,so my only experience is limited to the all-round TL071 and TL074.Thomas Henry himself used them in galore.
To my ears they sound thik and fat
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Cfish



Joined: Feb 24, 2016
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PostPosted: Tue Nov 15, 2016 5:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

All Hail Thomas Henrey. Giver of wisdom, often without compensation.

I will point out that the man who wrights the web article explanations deserves his due compliments.

But, back to easy analog controller circuits.

This is the EFM circuit that I could never get to work.

I want to figure out why?

What does the opamp circled in green do? Experimented a lot, makes no notable difference without it.

Never could get the OTA circled in red to do anything. This is the only project I have used the Chinese 13600s I bought in. They could be fakes.

Looks funny to me. The cap .01 blocks all but changes in voltage to the OTA. Which makes since for retrigering the gate. I just don't see how it can actually work, so I sort of gave up when it didn't.


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alanwilder81



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PostPosted: Tue Nov 15, 2016 6:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

yes Chris,
i remember you mentioning a project you couldnt get to work both GATE and TRIGGER of,hence giving up on it.is that really the case of a suspect counterfeit chinese chip lot?

Well, the only reason i haven't yet bought those CA 3080 or LM13700 off ebay is because of fear of scams Sad Sad .They are ridicolously cheap compared to the US or EU market but i definitely didnt feel like running the risk. I'm about to shell out the cash and get the bloody LM13700 off an italian seller,for around 1.50 dollars each. Not bad i guess Smile
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PHOBoS



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PostPosted: Tue Nov 15, 2016 6:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

ow that's easy, it's an ehm wait, what ?! scratch
The 0.1uF capacitor does indeed make some sense in triggering the S&H everytime a key is pressed, I don't know why an OTA is being
used there though especially in the way it is connected. And I would say the GATE out is actually a TRIGGER out. But the opamp you circled
in green ?, I can't make sense of it. Almost looks like a connection is missing but it is probably just a connection in my brain. Would be nice if
someone could explain it (the circuit, not my brain).

(1,50 is not a bad price for an LM13700 and it is a nice chip)

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