Building Look Mum No Computers 3340 Simple VCO

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nigel
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Post by nigel » Tue Jul 02, 2019 6:19 pm

Bardan wrote: Now i didn't dare to plug it to the supply that fires out ~14V..

How insignificant is this 2V difference in a modular synth application?
A lot of circuits designed for Eurorack +/-12V power will run quite happily on the +/-15V used in some other formats, so 14V will probably not do any harm. However, the fact that the power voltages are not symmetrical may make it impossible to calibrate a circuit, or just stop it working correctly.

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Post by Schlumpfhut » Wed Jul 03, 2019 12:32 am

If you are unsure check the datasheets of the ICs and other relevant components. They contain information on operating voltages.

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Post by Bardan » Fri Jul 05, 2019 8:16 pm

nigel wrote:
Bardan wrote: Now i didn't dare to plug it to the supply that fires out ~14V..

How insignificant is this 2V difference in a modular synth application?
A lot of circuits designed for Eurorack +/-12V power will run quite happily on the +/-15V used in some other formats, so 14V will probably not do any harm. However, the fact that the power voltages are not symmetrical may make it impossible to calibrate a circuit, or just stop it working correctly.
The thing is, i have two power supplies, they both are symmetrical but one is giving me +/-12V and the other one +/-12V.. so i guess i just made an hybrid between 5U and Eurorack lol

Thanks for your help! :)

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Post by Thinredline » Tue Jul 09, 2019 11:59 am

I actually made a stripboard version of FC's power supply based off of their schematic. The LEDs in the circuit have been a lifesaver for me, as they will tell me if I have a short somewhere. Normally both are on when everything works properly, but if I have a short somewhere one of them will turn off, prompting me to cut the power! If you have stripboard and extra parts you can always build another psu module. And yeah, if you read voltage from either the 7812 or 7912 w/nothing connected you will see a little higher voltage due to no load being place on them. I'd say the one reading ~14v, check your resistors to make sure none of them got damaged at all.

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Re: Building Look Mum No Computers 3340 Simple VCO

Post by m1kachu » Sun Apr 12, 2020 1:59 pm

zarar wrote:
Fri Aug 10, 2018 6:43 am
Hi!

Plugged in some headphones in the Square output jack and plugged the power in... nothing, just a very very slight static hum.

Here's a link to the build instructions:

https://www.lookmumnocomputer.com/proje ... iy-simple/

Hi Zazar! I'm, having the same issue with square output.

I found another man able to make this module according to Sam's scheme, but he doesn't seem to have this issue...
http://modular.ob1techno.com/2019/04/04 ... ototyping/

Did you find a solution for the square out?

Thanks a lot!

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Re: Building Look Mum No Computers 3340 Simple VCO

Post by infinitemachinery » Sun Apr 12, 2020 6:11 pm

m1kachu wrote:
Sun Apr 12, 2020 1:59 pm
zarar wrote:
Fri Aug 10, 2018 6:43 am
Hi!

Plugged in some headphones in the Square output jack and plugged the power in... nothing, just a very very slight static hum.

Here's a link to the build instructions:

https://www.lookmumnocomputer.com/proje ... iy-simple/

Hi Zazar! I'm, having the same issue with square output.

I found another man able to make this module according to Sam's scheme, but he doesn't seem to have this issue...
http://modular.ob1techno.com/2019/04/04 ... ototyping/

Did you find a solution for the square out?

Thanks a lot!
What's the voltage on pin 5?

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Re: Building Look Mum No Computers 3340 Simple VCO

Post by m1kachu » Mon Apr 13, 2020 3:44 pm

Sorry it was a noobs mistake, one of the TL072 socket pins wasn't soldered properly.
Now everything works fine, but along with troubleshooting I googled another implementation, that claims it has all LMNC errors fixed with added sync input and SIN output:

http://electro-music.com/forum/topic-70555-25.html
Image

it's way less compact and I prefer sticking to a compact design, so I followed this schematics:

http://modular.ob1techno.com/2019/04/04 ... ototyping/
Image

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Re: Building Look Mum No Computers 3340 Simple VCO

Post by m1kachu » Wed Apr 15, 2020 4:22 am

So I built a VCO according to the picture above.
There are 2 issues/questions now:

1) When I connect the 100K potentiometer (marked Frequency in the picture), the minimum pitch becomes ~4 octaves higher than it is with the pot disconnected.
It's obviously due to that 12V come through 100K pot and 100K resistor, but affect the pitch of the 3340IC.

2) I'm using Beatstep 1 as MIDI to CV converter and can't get it produce C note across even 2 octaves.
For example, I tune the C1 note to play C, but next octave C plays G etc.
Looks like CV gives 0.8volts per octave, but I've tested the Beatstep CV output. It gives exact 1 volt per octave (my best $30 bucks investment so far lol)

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Re: Building Look Mum No Computers 3340 Simple VCO

Post by socom93 » Wed Apr 15, 2020 4:50 am

m1kachu wrote:
Wed Apr 15, 2020 4:22 am
So I built a VCO according to the picture above.
There are 2 issues/questions now:

1) When I connect the 100K potentiometer (marked Frequency in the picture), the minimum pitch becomes ~4 octaves higher than it is with the pot disconnected.
It's obviously due to that 12V come through 100K pot and 100K resistor, but affect the pitch of the 3340IC.

2) I'm using Beatstep 1 as MIDI to CV converter and can't get it produce C note across even 2 octaves.
For example, I tune the C1 note to play C, but next octave C plays G etc.
Looks like CV gives 0.8volts per octave, but I've tested the Beatstep CV output. It gives exact 1 volt per octave (my best $30 bucks investment so far lol)
Hey ! Nice project, I hope you will succeed, i will try to help you with what i've learned using the AS3340 :

1/ You get the right answer ! I would advice to use this 100k pot as a voltage divider, you will have 1 on GND and 3 on +12V (or maybe less) and 2 as out. This way, when turned off you will get a lower octave.

2/ the Problem with a lot of "simple schematics" like the one from LMNC is that there is not a real tuning trimer.
Your 10k trimer is not there for tuning the pitch but to calibrate the 1V/OCt. So first you have to calibrate that (Kassutronics as a really good calibration explanation)
But then, you have to set the initial (OV cv) voltage. You should had another trimmer so you can change the initial voltage at pin 15. Put a 100k trimmer (set a variable resistor) and a 220k in serie to pin 15. This way you ill be able to tune the pitch of your VCO.

Wish you all the best

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Re: Building Look Mum No Computers 3340 Simple VCO

Post by m1kachu » Sat Apr 18, 2020 4:34 pm

@socom93 thank you so much for the help!
1/ You get the right answer ! I would advice to use this 100k pot as a voltage divider, you will have 1 on GND and 3 on +12V (or maybe less) and 2 as out. This way, when turned off you will get a lower octave.
Indeed that helped. I updated the layout with this ground wire.

Image


2/ the Problem with a lot of "simple schematics" like the one from LMNC is that there is not a real tuning trimer.
Your 10k trimer is not there for tuning the pitch but to calibrate the 1V/OCt. So first you have to calibrate that (Kassutronics as a really good calibration explanation)
But then, you have to set the initial (OV cv) voltage. You should had another trimmer so you can change the initial voltage at pin 15. Put a 100k trimmer (set a variable resistor) and a 220k in serie to pin 15. This way you ill be able to tune the pitch of your VCO.
As for tuning, I still don't get your advice. The Pin 15 is already juiced by this 100K pot (+ 100K resistor), that lets a portion of 12V to come through, isn't it?


Currently my build looks like this.
I found having sockets for all external connections very useful, as I can change the pots value easily.
Image

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Re: Building Look Mum No Computers 3340 Simple VCO

Post by m1kachu » Sat Apr 25, 2020 11:17 pm

socom93 wrote:
Wed Apr 15, 2020 4:50 am
m1kachu wrote:
Wed Apr 15, 2020 4:22 am
So I built a VCO according to the picture above.
There are 2 issues/questions now:

1) When I connect the 100K potentiometer (marked Frequency in the picture), the minimum pitch becomes ~4 octaves higher than it is with the pot disconnected.
It's obviously due to that 12V come through 100K pot and 100K resistor, but affect the pitch of the 3340IC.

2) I'm using Beatstep 1 as MIDI to CV converter and can't get it produce C note across even 2 octaves.
For example, I tune the C1 note to play C, but next octave C plays G etc.
Looks like CV gives 0.8volts per octave, but I've tested the Beatstep CV output. It gives exact 1 volt per octave (my best $30 bucks investment so far lol)
Hey ! Nice project, I hope you will succeed, i will try to help you with what i've learned using the AS3340 :

1/ You get the right answer ! I would advice to use this 100k pot as a voltage divider, you will have 1 on GND and 3 on +12V (or maybe less) and 2 as out. This way, when turned off you will get a lower octave.

2/ the Problem with a lot of "simple schematics" like the one from LMNC is that there is not a real tuning trimer.
Your 10k trimer is not there for tuning the pitch but to calibrate the 1V/OCt. So first you have to calibrate that (Kassutronics as a really good calibration explanation)
But then, you have to set the initial (OV cv) voltage. You should had another trimmer so you can change the initial voltage at pin 15. Put a 100k trimmer (set a variable resistor) and a 220k in serie to pin 15. This way you ill be able to tune the pitch of your VCO.

Wish you all the best
Good day guys! Hope you're doing well!

I tried adding some voltage to the PIN 15 according to @socom93's advice... I still don't understand does it help or not with fine-tuning, but raises the minimal pitch a lot :-)
I read the Kassu guide, but It doesn't seem to work for me...

Image

Do I understood the idea right? Maybe any other ideas, how I can get an octave range feeding 1-2-3-4-5... volts?

Thanks a lot! Be safe!

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Re: Building Look Mum No Computers 3340 Simple VCO

Post by socom93 » Tue Apr 28, 2020 11:01 am

Maybe I didn't get you right the first time. Your 10k trim pot is there to get the 1V/Oct and only him.

So first, you trim the 10k pot : use the calibration given by kassutronics. (note that every frequency pot and FM should be at a fixed position, like 0V)
Then, you trim the 100k pot to calibrate your starting frequency (note).

Tell me if that works for you, if not maybe send other pictures of your circuits we will figure out what is wrong

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Re: Building Look Mum No Computers 3340 Simple VCO

Post by m1kachu » Sat May 16, 2020 12:56 am

socom93 wrote:
Tue Apr 28, 2020 11:01 am
Tell me if that works for you, if not maybe send other pictures of your circuits we will figure out what is wrong
I finally got it right!

The wrong part was a shitty trimmer of a different type. After installing the proper trimming resistor with a super long run (probably 10 turns), I easily got the same note on 7 octaves!
The pitch fluctuates just a bit, but that's fine.

Thanks @socom93 for the help!

I'll share the final result a bit later, as I recently got a 3D printer (which is awesome!) and I want to print a panel for this VCO

Image

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Re: Building Look Mum No Computers 3340 Simple VCO

Post by socom93 » Sat May 16, 2020 4:28 pm

m1kachu wrote:
Sat May 16, 2020 12:56 am
socom93 wrote:
Tue Apr 28, 2020 11:01 am
Tell me if that works for you, if not maybe send other pictures of your circuits we will figure out what is wrong
I finally got it right!

The wrong part was a shitty trimmer of a different type. After installing the proper trimming resistor with a super long run (probably 10 turns), I easily got the same note on 7 octaves!
The pitch fluctuates just a bit, but that's fine.

Thanks @socom93 for the help!

I'll share the final result a bit later, as I recently got a 3D printer (which is awesome!) and I want to print a panel for this VCO

Image
Good Job !!! :yay: :yay: :yay:

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Re: Building Look Mum No Computers 3340 Simple VCO

Post by Studioalethea » Sat May 16, 2020 5:03 pm

Was it a wrong part or a defective/poor quality trimmer? Just curious.

I have a tendency to use knockoff ones from Tayda to prototype on the breadboard but then put legit Bournes with the desired pin orientation and horizontal/vertical orientation when I solder it up.

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Re: Building Look Mum No Computers 3340 Simple VCO

Post by m1kachu » Sat May 16, 2020 10:48 pm

Studioalethea wrote:
Sat May 16, 2020 5:03 pm
Was it a wrong part or a defective/poor quality trimmer? Just curious.
Hey, it was just of a different type, just as the pot in a left top corner (a radial one).
I wouldn't even call it a trimmer, 'cause it was just as a regular pot with about 320 degrees rotation.

The correct trimmer: https://www.digikey.com/product-detail/ ... -ND/666503

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Re: Building Look Mum No Computers 3340 Simple VCO

Post by rektagonal » Tue Jul 28, 2020 10:59 pm

Hello all! Took at a stab at building this from the OG design on Sam's site (with Square/PWM CV) as my first proper strip board module build. unfortunately I'm getting absolutely zero sound out of the module. I made a major noob mistake initially and wired all the pots on backwards (yikes) hoping this didn't fuck up the 3340 chip in any way. triple and quadruple checked all my wiring and considering I'm getting nothing at all outputting from any of the waveforms I feel like I've either made a totally stupid mistake or fucked my 3340. pics below for reference (placement of jacks and pots are purely for testing purposes, will mount to panel later, also, far left tab of the coarse tune pot is bent away, not connected to circuit). lesson learned: test with cheap knockoff chips before you buy the real thing?
IMG_2777.JPG
IMG_2778.JPG
IMG_2779.JPG
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Re: Building Look Mum No Computers 3340 Simple VCO

Post by Studioalethea » Wed Jul 29, 2020 2:09 pm

Measure all the voltages on each pin of the 3340 and report back. Wiring the pots backwards would probably not have a damaging effect on the chip. Step 1 is making sure you have +12V on pin 16 and -5V(ish) on pin 3. I'm trying to follow your traces for power but not quite seeing the flow.

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Re: Building Look Mum No Computers 3340 Simple VCO

Post by rektagonal » Wed Jul 29, 2020 4:33 pm

Studioalethea wrote:
Wed Jul 29, 2020 2:09 pm
Measure all the voltages on each pin of the 3340 and report back. Wiring the pots backwards would probably not have a damaging effect on the chip. Step 1 is making sure you have +12V on pin 16 and -5V(ish) on pin 3. I'm trying to follow your traces for power but not quite seeing the flow.
Ohhhhh shit I see what I did. When I adapted the board for use with Eurorack 10-pin, I jumped the + and - 12v to the rails above and below ground (black line) respectively. However, I failed to then cut the traces on the other side of my jumper pins, so the power is also going to the 2 rows on either side of ground (sending +12v to pin 5 of the top TL072 and -12v to pin 8 of the bottom TL072). This means -12v is also going to that 470R coming off pin 5 of the 3340. Who knows what havoc this could be doing on the circuit. Yikes. Well I guess worst case scenario is all 3 chips are fucked and I learned a good lesson :despair: :roll: Pics below for reference.

Thank you for asking about my power scheme or else I would not have caught this!
Screen Shot 2020-07-29 at 5.25.33 PM.png
Screen Shot 2020-07-29 at 5.25.14 PM.png
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Studioalethea
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Re: Building Look Mum No Computers 3340 Simple VCO

Post by Studioalethea » Wed Jul 29, 2020 8:55 pm

rektagonal wrote:
Wed Jul 29, 2020 4:33 pm
Studioalethea wrote:
Wed Jul 29, 2020 2:09 pm
Measure all the voltages on each pin of the 3340 and report back. Wiring the pots backwards would probably not have a damaging effect on the chip. Step 1 is making sure you have +12V on pin 16 and -5V(ish) on pin 3. I'm trying to follow your traces for power but not quite seeing the flow.
Ohhhhh shit I see what I did. When I adapted the board for use with Eurorack 10-pin, I jumped the + and - 12v to the rails above and below ground (black line) respectively. However, I failed to then cut the traces on the other side of my jumper pins, so the power is also going to the 2 rows on either side of ground (sending +12v to pin 5 of the top TL072 and -12v to pin 8 of the bottom TL072). This means -12v is also going to that 470R coming off pin 5 of the 3340. Who knows what havoc this could be doing on the circuit. Yikes. Well I guess worst case scenario is all 3 chips are fucked and I learned a good lesson :despair: :roll: Pics below for reference.
We've all smoked our share of chips. Hopefully not all is lost!

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Re: Building Look Mum No Computers 3340 Simple VCO

Post by smiler » Thu Jul 30, 2020 12:46 am

A common thing to do is to before you insert the ICs into their sockets is to probe the power rail pins in the sockets with the board powered up and make sure that you see the expected voltages.

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Re: Building Look Mum No Computers 3340 Simple VCO

Post by Studioalethea » Thu Jul 30, 2020 1:50 pm

smiler wrote:
Thu Jul 30, 2020 12:46 am
A common thing to do is to before you insert the ICs into their sockets is to probe the power rail pins in the sockets with the board powered up and make sure that you see the expected voltages.
I second this. Install ICs only after you have checked voltages on all the pins of the sockets.

Also, before you even connect to power, continuity test all the rail connections... are all the -12V connected together but NOT to Ground or +12V or Ground... all the grounds, etc. Protect those ICs.

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Re: Building Look Mum No Computers 3340 Simple VCO

Post by rektagonal » Thu Jul 30, 2020 5:49 pm

Studioalethea wrote:
Thu Jul 30, 2020 1:50 pm
smiler wrote:
Thu Jul 30, 2020 12:46 am
A common thing to do is to before you insert the ICs into their sockets is to probe the power rail pins in the sockets with the board powered up and make sure that you see the expected voltages.
I second this. Install ICs only after you have checked voltages on all the pins of the sockets.

Also, before you even connect to power, continuity test all the rail connections... are all the -12V connected together but NOT to Ground or +12V or Ground... all the grounds, etc. Protect those ICs.
I was a bit overconfident I think as there was no continuity between +/-12 and ground, so I assumed all was well.Was I didn't do was look for +/-12v where there SHOULDNT be +/-12v. A review of the proper pinouts for the ICs and checking before plugging them in would've solved this but I have most certainly learned my lesson.
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