Moog Light Synth V2

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Introduction: Moog Light Synth V2

About: I've always liked pulling things apart - it's the putting back together again that I have some issues with!

This synth is a pulse width modulated oscillator, routed through a light-controlled resonant low pass filter. The "growling" oscillator tonality is supplied via a PWM and an awesome high-resonance low pass filter. The oscillator is controlled via 2 Light dependent resistors (LDR) and gives you the ability to create amazing musical expression. The 10 “keys” give you different tones and allow you to play it like a keyboard

Also included is 2 Hex inverter drones, supplied via a 40106 IC. The 2 two adjustable drone oscillators give this synth three oscillators in total. You also have the ability to turn off the 2 hex inverter drones and just play around with the other oscillator.

I also added the ability to play the synth just with one potentiometer and the LDR’s. When combined with the echo/reverb feature you can really get some fantastic sounds from the synth.

Just watch the YouTube clip and you’ll see what I mean

Lastly, I have to give a shout out to Pete McBennett who designed this awesome circuit. Check out his YouTube channel here

You can check out the first one I built here

Step 1: Parts

The Moog Synth

I have designed a PCB for this circuit so all you need to do is to send the gerber files to a PCB manufacturer like JLCPCB (Not affiliated) who will print the board for you. The circuit and board were put together using Eagle and all of the files including the schematic, board and gerber files can be found in a Google Drive link in the next step

The parts list is also available in my Google drive as an excel file and I have included as a PDF in this Instructable.

The Rest of the Parts:

1. Potentiometer Knobs - eBay

2. Echo/Reverb module - eBay

3. 2 X 50K Potentiomeners (for the echo/reverb module) - eBay

4. 10 X momentary switches - Ali Express

5. 2 X SPDT switches - eBay

6. Wire. I like to use computer ribbon cable. you can buy it on Ali Express or just visit a place where e-waste is dumped to get it for free

7. Li-po Battery - eBay. I used an old mobile battery to power the synth. They work great for projects like this and you can get them for free. check out this 'ible on how to find them and use them

8. Charging and voltage regulator module - eBay

9. Micro USB module - eBay

10. Water Decal - eBay

11. 40mm X 80mm X 10mm length of hard wood (for making the case) - Hardware store

Step 2: The Moog Style Synth - Circuit and Board

As mentioned in the previous step, you can find the schematic and board (designed in Eagle) in my Google drive. If you want to you can play around with these yourself in Eagle. I have also saved the gerber files which is what you need to send to a PCB manufacturer to print the board

UPDATE Dec 2020

I have also included an updated PCB which has a tunable trimmer pot for each of the 10 keys. The resistor values have to be quite precise in order to have it in tune and using a trimmer for each key allows you to fine tune the synth. The board can be found in the Google drive link above and is in a folder called Moog Light Synth - Tunable Pots. I also included some test points against each trimmer so you can easily measure the resistance with a multimeter.

I have tried to make the board as small as possible and it has had a few revisions since the initial one that I used so will look different to the images. I've added an LED to indicate on/off and also a switch to turn on/off the drone oscillator plus a few more additions

I also used pin headers for all of the auxiliary parts like pots and LDR's. You can solder wires directly to the board if you like.

Step 3: Soldering the Components to the Board

Steps:

1. I always start with adding the resistors first to the board. They are usually the lowest part on the board and it makes it easy to do these first. Plus there are a heap of them so it's good to get them out of the way

2. Once I have all the resistors soldered I then work on other low profile parts such as the diodes.

3. Next I add the IC holders pin headers

4. After that I start to add on the taller components like the capacitors and transistors.

5. Lastly I add in the IC's and give it a test. Adding pin headers makes it pretty easy to test, you just need some female jumper leads and add the components onto the ends of these. It's always good practice to test any circuit you have made before you go the whole way and add it to the build. Nothing worse trying to troubleshoot when there are wires everywhere.

Step 4: About the PCB

The attached image shows the different connections to the PCB and how they are connected to the components. I've also included a glossary below which will help you understand what each of the connections to the PCB are for and what they do.

Out = Audio Out. To be able to hear the synth you will need to connected it to an amplifier or portable speaker. This connection will later be connected to the "in" on the echo Reverb Board

Base = Drone oscillator, 100K potentiometer

Tenor = Drone oscillator, 100K

Oscillator on/off = This is used to turn off the drone oscillator

LED = Power on/off indicator

Tone = Master tuning control, 50K potentiometer

PWM = 100K trimmer potentiometer. This "tunes" the pulse width modulated oscillator. You'll need to adjust this until you find the sweet spot

LDR 1 & 2 = This is where the Light Dependent Resistors are connected.

PWR = 9v power source to run the synth

Single/Multi Control = I added this so you can control the synth from just one potentiometer. You can also use the Tone pot to play around with the sound as well when using the single pot control. This is a lot of fun when you have echo on.

Switch = This turns on & off the single multi control

100K = This is the potentiometer that controls the synth when one single play

Switch 1 = One leg on each of the 10 momentary switches used to play the synth need to be connected together. They are then connected to the "Switch 1" connection on the PCB

Switch 2 = Consists of 10 connections, each on needs to be connected to one of the legs on the 10 momentary switches

Step 5: Moding the Echo/Reverb Module

I did an Instructable on how to mod the echo and reverb module which can be found here. It's not really a mod per se, more just now to had the echo pot and what resistor to remove. I won't go through this in much detail here so if you need further instructions, check out the 'ible above.

Steps:

1. First you'll need to remove one of the SMD resistors (R27). I do this with an exacto knife and it seems to work well each time. Just get the tip of the knife on the side of the resistor and gently pry it up

2. Next, you will probably need to remove the reverb port which is soldered onto the board. If however you are able to connect the pot to the panel without having to remove it then just leave it on. If you have a de-soldering device then use this as the traces have a tendency to lift if you just add a soldering iron to it. If you don't then use a pair of wire cutters and just cut it away.

3. If you look on the board you will see that along with the 3 solder points for the pot that you just removed, there are 3 others near it. These ones are for controlling echo. You'll need to solder wires onto each of the solder points for reverb and echo control.

4. That's all you need to do for the moment. later on you will need to connect the wires to the each and reverb pots.

Step 6: Creating the Front Panel

To design the panels I used Inkscape, a vector graphics editor which you can download for free! There's a lot of information available on how to use it and I would suggest you do a couple of the basic tutorials to familiarize yourself with the different features if you haven't used it before

I did a couple video's on how to design knob scales and also make a front panel which I have included above.

There is even an extension that you can download so you can design knob scales easily and simply which you can download here

However, if you don't want to bother learning how to design your own, you can always just use mine which I have attached as a PDF. I have also includes the Inkscape file so you can play around with that as well if you want to.

Step 7: Adding the Water Acrylic to the Front Panel

Steps:

1. Once you have your design you should print a few copies of it on normal A4 paper. This will allow you to use it as a template to decide how big to cut the opal acrylic. The acrylic will in the end be the front panel. I used opal coloured acrylic but you can use any colour you want.

2. Cut the acrylic panel to the right size. I used a band saw tio do this but you could do it by hand as well. Last time I did this I pre-drilled the holes. However, it makes it very hard to line up the decal so don't worry about pre-drilling.

3. Next, print the panel design directly onto decal paper and leave to dry for 30 minutes. You can also spray with clear acrylic as well to protect the ink but I didn't bother.

4. Add the water decal to the acrylic by Placing the decal into some warm water and once it start to lift off, carefully slide it onto the acrylic. Ensure everything is lined up right and remove any excess water.

5. Once fully dried, sprayb some clear acrylic paint on the panel and repeat 2 to 3 times.

5. Mark all of the sections with a punch that need to be drilled.

6. Drill out the holes to the right size using a stepped drill piece.

Step 8: Making the Case

used some strips of hardwood to make the case. It's used for edging and can be brought at any hardware store. The dimensions are 40mm X 10mm X 1000mm

Steps:

1. The first thing you need to do is to cut a groove along the wood in order to secure the panel into. I use a dremel with a router attachment to do this.

2. Secure the wood with some clamps and run the bit near the top of the wood. Take your time and make sure you keep the dremel nice and straight.

3. Measure and cut the wood to size. The best way to do this is to just slip in the front panel into the groove of the wood and measure where to make the cuts

4. Before you secure the front panel into the case, paint the top section and inside. When the panels in place it will make it hard to do and you might get paint on the panel. I used some clear stain to highlight the grain in the wood. The reason why you don't paint it all is you need to sand the wood once the case is complete.

5. Place the front panel into the grooves of the wood and use some PVC to glue it together. If you find the panel is a little big and the wood doesn't right then just remove a little of the acrylic along the edge with a sander.

6. Clamp and leave to dry for 12 hours.

Step 9: Sanding the Case and Making a Base

Once the glue is dry you can then use a sander to make the edges nice and clean. I also rounded off the top sections which gives it a bit of a softer look.

Steps:

1. If you have a belt sander then this will be an easy job. If not, a hand sander will suffice

2. Sand each of the sides of the case until the wood is smooth and level.

3. To round off the top sides of the case I agauin used to sander. Just rotate the section to be rounded on the sander until you get the desired effect.

BE CAREFUL - Check out the last image to see what I mean. I managed to touch the sander onto the front panel and scratched the name of the synth!

4. To finish, use some 400 grit sandpaper to smooth everything out.

5. The base is just a piece of ply wood. First, measure and cut to size

6. Place onto the bottom of the case and add some screws to hold it in place.

7. Use the sander again to smooth the edges and make them level with the case.

8. Un-screw the base and make a little mark on both the base and case so you know which ends go together

Step 10: Adding the Componets to the Front Panel

This is pretty straight forward, just be careful not to scratch the front panel when you are scecuring the components.

Steps:

1. There are 10 momentary switches to add so you may as well start with these to get them out of the way

2. Next add the pots and the 3 SPDT switches

3. Then comes the audio socket

4. Lastly, you can add the potentiometer knobs as well.

Step 11: Adding the Circuits and Battery to the Case

Now that you have the case, panel and PCB's done, it's time to start thinking about connecting everything together. Just before that happens though, you'll need to secure the battery and PCB's to the base of the synth.

Steps:

1. Lay all of the parts onto the back panel and work out the best place to locate them. For example, if you add the micro USB charging module at the top, then make sure that you locate the battery at the top as well.

2. Once you are happy with the layout, use some good, double sided tape and stick everything down. The great thing about using tape is it's easy to pull off the parts from the back of the wood if you need to. You could also screw down the boards later if you wanted to once everything has been tested

3. To be able to charge the battery, you will need to add a micro USB module somewhere on the case. The easiest way to do this is to make a small cut-out with a flat file at the bottom of the case. You can then add a little superglue and stick it in place. Later this will be connected to the charging module.

Step 12: Connecting Everything Together

Steps:

1. Lay the top and bottom sections of the case next to each to each other.

2. First thing you should do is complete any soldering that needs to be done. Solder the wires from the echo/reverb module to the relevant pots on the front panel

3. Next, stick the battery charger and voltage regulator module on top of the battery. If you want more details on how to use this module then I've done an Instructable on this as well which can be found here. Wire-up the battery to the module and connect to the on/off switch. Also set the voltage to 9V on the module via the micro pot on the module. You'll need a multimeter to do this

NOTE: The module will always draw a little bit of power so I always connect the on/off switch from the battery to the module. That way you stop the module from drawing power from the battery and draining it over time. it's only a very small amount but it will drain it over a few weeks

4. You'll also need to add a couple wires from the echo/reverb module to the output on the charging module to power it. Also connect the positive and ground from the moog light PCB to the out on the charging module

5. Solder any wires needed to the switches as well. If you are confused at all then reference the image on step 3.

6. Once all of the soldering is done, you can start to connect the pots up to the PCB. Again, reference the image on step 3 for how to orientate the pots.

7. Test to make sure everything is working as it should before closing it up.

NOTE: Remember that you need to set the PWM trimmer pot. To do this, turn on the synth and slowly turn the trimmer pot. Once you hear some sound, push down on one of the buttons until you get a clean, modulated sound.

TIP - if you find that the echo/reverb isn't working, disconnect it from the battery and connect it again. Sometimes they need resetting before they will work.

Step 13: So How Do You Work the Thing!

That's a good question! Turns out luckily that its very easy to play. I'll go through what each of the controls do and some of the quirks that I found that you can play around with as well

Steps:

1. First lets play around with the 10 keys. make sure that the single/multi pot is turned off

2. Place you fingers over the 2 LDR's and start to play one of the keys. You should get a nice deep growl of a sound. Move your fingers away from the LDR's and the PWM will give you different tones

3. Turn on the drone synth and you'll get a low drone. play around with the base and tenor until you get the oscillators in sync or close to.

4. Now you can play the PMW synth with the drone synth in the background

5. Now turn up to 7 both he reverb and echo and start playing the synth. You will notice the sounds are fatter and have more dimension due to the echo. change the echo length and speed by turning the echo pot

6. Turn the Tune pot to change the pitch of the PMW synth. You can have it play higher or a real deep base low

7. Ok - so now it's time to play around with the single/multi pot. First turn it on. You'll hear the PMW synth constantly running.

8. Place your finger's over the LDR's and slowly turn the single/multi pot. Give it some echo as well and you'll get some awesome droney sounds coming out of the synth. Now slowly turn the tune pot to change the pitch. Give it a quick turn and the echo will kick in.

9. You can even play the keys at the same time and get some funky sounds coming out of the synth

10. There is a small glitch that I found in the tune pot. If you tune the pot to about 3 you'll notice that the synth pulses. Play around with this as it's almost like a basic arpeggiator which you can play to.

11. This is just some basic's to get you started. There is plenty more that this little synth can do - I'll leave it up tp you to experiment and find them

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    28 Comments

    0
    AutoSol
    AutoSol

    Question 11 months ago on Step 2

    Well done!
    I was not able to find the tunable pot version of the board on your Google drive.
    Please add it.
    Thanks,
    AutoSol

    0
    lonesoulsurfer
    lonesoulsurfer

    Answer 11 months ago

    It's on the drive - in a separate folder. Click on the link and at the top there is a folder which has all of the info you need

    0
    lonesoulsurfer
    lonesoulsurfer

    Reply 7 months ago

    Still waiting on a couple parts to arrive. I've got the boards so will put one together and see how I go. If I get the same issues then will take another look at it.
    Glad you got it to work though

    0
    AutoSol
    AutoSol

    Answer 8 months ago

    Lonesoulsurfer,
    I found it, thanks.

    I made the tunable pot PCB version per the schematic but is does not work, with these symptions:
    >Single Multi only works on switch 10.
    >Switch 1 always works
    >Tune pot only works in center of rotation
    Comparing the resistor schematic to the tunable pot schematic I discovered that the resistor schematic only has the first switch connected to opamp 1c1b inverting input while the tunable pot schematic has all pot legs connected together to opamp 1c1b.
    This would account for the behavior i am seeing and think will need to modify the PCB to be like the resistor schematic to get it to work.

    Have you tried the tunable pot schematic? If so what results do you get?
    Any other comments?

    Thanks,
    AutoSol

    0
    lonesoulsurfer
    lonesoulsurfer

    Reply 8 months ago

    Hi AutoSol,

    That's a shame! I have started to build the tunable pot version but am waiting on a couple parts to finish it. If you take a look at the schematic below which is by Pete McBennett, he originally added pots to this synth instead of resistors. How this is wired-up is pretty much the same as I have done with the tunable pot version.
    You could be right though, the issues you are having could be due to how the pots are connected together...
    I'll finish mine off in a week or 2 and will test it to see if I have the same problem.
    I'll let you know how I go.

    LDRsynth.JPG
    0
    AutoSol
    AutoSol

    Reply 7 months ago

    Hey lonesoulsurfer,
    After cutting foils and adding jumpers to mimic the connections on the resistor schematic the synth now works as you presented. The tunable pot schematic was not correct and needs to be updated for anyone attempting this implementation.
    Have you tried your tunable pot version yet? Results?
    Thanks,
    AutoSol

    0
    westeraj
    westeraj

    Question 9 months ago

    Amazing project! I love your work.
    I have a question. I'm wondering about including the vactrol arpeggiator circuit from your first version of the instrument in this one for added sound effects. To do that, I assume you would just connect the leads to the LDR ports on the new circuit board. But where would you connect the power leads for the vactrol circuit? Is there enough power to run it in series with the mainboard or would you have to adjust anything else? Thanks so much!!

    FW1V2GIK6KVIU70.jpg
    0
    lonesoulsurfer
    lonesoulsurfer

    Answer 9 months ago

    Hey there.

    Power can be connected directly to the power diving the moog circuit. def will have enough power. The main thing you really want to do is be able to switch from the LDR's on the Moog to the vactrols on the arpeggiator.

    0
    peluzcano
    peluzcano

    10 months ago

    Can you explain what I have to do to adjust the 100K PWM potentiometer and leave it still without moving it?

    Sin título.jpg
    0
    lonesoulsurfer
    lonesoulsurfer

    Reply 10 months ago

    The 100k timmer pot needs to be adjusted once the synth has been built. You use a small screwdriver to adjust the pot - there is no need to touch it once it has been adjusted and it won't move once it has been adjusted. To tune it in - all you have to do is to push one of the keys and turn the pot until you hear the sound. There is a sweet spot where the filter is humming and you'll hear it once you start to turn it.

    0
    peluzcano
    peluzcano

    10 months ago

    Hello there is one thing that I do not understand that it is the working voltage of the whole circuit ......
    In the drawing there is a 9V battery, and you explain a 3.7V lithium-ion mobile phone battery with its charger circuit .......
    Where we are, does the whole circuit work at 3.7V or at 9V ????

    0
    lonesoulsurfer
    lonesoulsurfer

    Reply 10 months ago

    So the working voltage is 9V. You can power it from a 9V battery if you want to. However, I used a 3.7v mobile battery and a buck booster to increase the voltage to 9V. I did this so I could have a rechareable battery in the synth instead of having to have to replace a 9V battery every time

    0
    eburman
    eburman

    Question 11 months ago

    I think I'll submit an order to JLCPCB for the revised PCB version with the individual tuning pots. Maybe I'm overlooking where you mentioned it, but what is the resistance range of the trimmer pots that you are using for the new version? Also I don't see any details regarding the two LDR's. Do you remember what the resistance range and size is for the particular LDR's that you used? Maybe you have a link to the exact ones you used? Thanks for your help!

    0
    lonesoulsurfer
    lonesoulsurfer

    Answer 11 months ago

    I think that's the best way to go. However just be warned, I haven't tested the PCB yet, although I don't foresee any issues with it. The resistor range I included on the board and go from 3.40K to 38.3K. You will need 9 X 10K trimmers and 1 X 50K trimmer.

    In regards to the LDR's - I must admit I just brought some cheap one I found on eBay. I've measured the resistance on them and it is reading aprox 200R to 10K resistance.

    Hope that helps!

    0
    eburman
    eburman

    Reply 11 months ago

    Yes thanks! That helps a lot. I think I probably have some LDR's in my parts box that are in that range. As for the PCB I think I'll stick with the old version (which I already have) and wait until you've got the newer one checked out. I can always upgrade later.

    0
    lonesoulsurfer
    lonesoulsurfer

    Reply 12 months ago

    No worries. done

    0
    AleCss
    AleCss

    Reply 11 months ago

    Hi, very beautiful project! Where can I find the gerber files?

    Thanks

    0
    lonesoulsurfer
    lonesoulsurfer

    Reply 11 months ago

    Thanks. Gerber files can be found in step 2 in the "Google Drive" link

    0
    eburman
    eburman

    12 months ago

    This sounds like a fantastic project! I plan on building it. Thanks for taking the time to make a very detailed tutorial!. I have a suggestion though. Why do you have the drill file separate from the Gerber files? When I submitted the Gerber's to JLCPCB they rejected it because the drill file weren't included. I came to realize that I have to take the drill file out of the drill file folder and include it with the Gerber files. Those of us who haven't had a lot of experience with PCB fabrication are not aware of these things and I'm sure it's very confusing to a lot of beginners. Why not have a complete and consolidated set of compressed files that are good to go that newbies like myself can simply drop into the JLCPCB order page? Or maybe I'm doing this wrong?