before starting Today, we’re going to build together the 2nd FX Teacher pedal ! This is the Trémolo pedal, released at NAMM 2020.So of course, it is not the easiest project to get started, but nevertheless, we designed it so that everyone could get there ! If this is your first FX Teacher kit, I advise you to check out the blog and discover our methods, I consider in the rest of the article that all this will be largely acquired ! the essential tutorials If you have already made a dozen of kits and a simple BOM is enough for you, we also thought of you, skip the pedago/theoretical part and download directly the doc ! the trémolo kit doc Whether you’ve already soldered a dozen of pedals or not, a bit of theory never hurts, you will find all your satisfaction in our latest article on tremolo ! a tremolo, how does it work ? Disclaimer : If you’re in trouble with a step or you don’t understand something, we will be happy to help you. For this, leave a comment with your request on this blog post. This project is even so DIY, so it is up to you to make your own decisions and responsibilities, and to check what you are doing before going ahead. You will be answered as soon as possible and this answer will allow other readers to go forward. Don’t be surprised if your comment doesn’t appear immediately, we have to validate it to avoid spam from certain robots. To recap, no emails, no chat, no calls regarding DIY, only requests on comments section please. Otherwise, it’s unmanageable for us.Please also check that your request has not been treated, also that your tensions are good and that you have followed all the steps 🙂If you feel that you need to be coached, you can join one of our masterclasses, they are made for you ! 😉 plan the trémolo’s design, the different pcbs, and their interactions.motherboard assembly and testingmotherboard canning and testingaudio board assembly and testingfinalize the pedal the trémolo’s design the sections Tremolo effects were a real challenge for our team ! As described in our article on how they work, there are 3 important blocks : the power supply stage, the creation of digital LFO, and analog amplitude modulation.Each of these stages has been a challenge for us. After 1 year of intensive research and 3 years of occasional prototyping… We decided to test a new design with 2 PCBs ! The inside of the Trémolo when it is finished ! the advantages Each board has several roles, to sum up, the daughter board (the black one on the picture) is in charge of the analog signal processing. And, the mother board (the green one) is dedicated to power supplies and digital signals. CARTE MÈRECARTE FILLEGénérer la LFOModulation analogiqueGérer les alimentations +9V/-9V/5V/2V5/GND/DGNDTrue bypass à relaisLED RVBTrimpotsContrôles/InterfaceCâblages Concretely, the idea of having separated the process into 2 boards brings us several advantages : no digital noise by completely separating the groundsdouble the space to insert components !simplicity of canningeasier after-sales servicevery clean wiring ! But in addition, having moved to digital technologies, we can now create an infinite number of LFOs, completely crazy functionalities and more…So even after more than a hundred pedals manufactured, we find that this new process is really nice ! the technologies used The digital board as you’re about to receive it ! There are about a hundred components in this pedal and even more in the Ages our harmonic tremolo !We could probably manage to fit all the components on the Trémolo by using through hole components on 2 PCBs but it could be quite difficult… Then anyway, for the digital part there are some technologies that are quite difficult to find in through hole mounting.We consequently decided to entirely assume this technology and to make sure that the digital part is at most in SMD (Surface Mounted Components) !And of course, getting you to solder this, it’s a horor ! So you get a motherboard with a lot of small components pre-soldered in the factory, and you will have to add to the board only through hole components that are either too big to be SMD, or connectors/pots, or the microcontroller that we want to reprogram at will. motherboard assembly Okay, let’s go for real this time ! As described above, this board is very rich in components and features.Therefore, a large part of the components are already soldered, the smallest ones, and the others to be soldered will be the biggest of them, the through hole ones. Considering the technical difficulty of both hardware and firmware, and the intense technical and far away from audio aspects made us decide to focus on making this board rather than understanding it in every detail. So you must be having 4 bags : components to be soldered on the top of the boardcomponents to be soldered on the bottomthe wiring for canningthe screws 1st bag Here is the list of components to be soldered “at the bottom” of the PCB : 1st bag BOM. We will go on to consider that you’ve read the various blog posts. I am still going to remind you about the delicate components and you should avoid soldering upside down. 1st bag – electrolytic capacitors the value can be read on the side of the capacitor. the + is drawn on the board and it corresponds to the longest leg of the capa. Here is the expected result for this step : You have to push them in well so they don’t stick out too much. 1st bag – potentiometers and switches For this step, our supplier made us custom-made pots ! You will see it’s fabulous, they fit together and stay in place without any trouble !For the toggle switch unfortunately we couldn’t do as well but it’s already convenient and without wires. So there’s a video with a trick in this article (which you’ve already checked, of course !) : apprendre à souder comme un « pro » ! And here is the expected result of this step : Of course the pots and switch are straight, well aligned. If you want to check the accuracy of your alignment, it has to fit in the enclosure of your pedal ! Once soldered, we will prepare the nuts for the next step of the assembly.If you look carefully, the toggle switch is 12mm high while the pots are only 10mm high. A nut is 2mm, so we will use them to compensate the height : for each potentiometer, leave one nut fully tightened. this brings us to 12mm high.keep the washer and the 2nd nut of the pot aside for later. this will lock the pot on the enclosure.for the toggle switch, don’t leave anything on it, it is already at the right height.for the rotary switch, you have to do the same as for the pots. 2nd bag Now we move on to the TOP layer of the PCB ! Here is the BOM : 2nd bag BOM. We are lucky there are few components, but everything is a bit technical ! Above all, don’t do like some participants of the masterclass <3, don’t solder the chip on the wrong side.If you have any doubt, in 99% of the cases the component is drawn on the side where you have to insert it. 2nd bag – integrated circuits A little reminder about integrated circuits. A notch is drawn on the board, the same notch is on the IC socket. Once soldered, the chip can be inserted into the socket. To know the direction of implantation, you have to rely on the notch or the point drawn on the chip. Easy, isn’t it ? As the ATMEGA has 28 legs, it is not necessarily easy to push it onto the socket. The components are delivered with the legs bent slightly outwards.The easiest way to insert it is to push slightly in one row. Then you push on the chip to bend the legs inward. And finally, once the other row of legs is facing the holder, you can finally insert it !If you’ve damaged a leg, be careful with the flat pliers to put it back in the right place, it’s rather fragile ! 2nd bag – slide switch Nothing particular at the soldering stage, just put it on the right side to have access to it afterwards. Let’s go ! Be careful not to overheat it, it might make a bad contact. As a reminder, this switch allows you to choose to connect a Spinner or a Tap.For the Spinner, the switch must be at the upper position and inversely for the Tap. 2nd bag – female connectors So for this step, the most important thing is to be as straight as possible ! The female connectors once soldered. These connectors will be used to connect the motherboard and the daughterboard. On the other side there will also be male connectors. If you haven’t soldered them straight, it will be difficult to insert them. 3rd bag You know what ? We are not far from being able to test if the digital board works ! Yeah, all we have to do is power it up ! 3rd bag BOM. 3rd bag – motherboard test To test your board, take the red wire and solder it on the +9V pad. Then the 7cm black wire on the G pad. You can solder it on one side or the other, it is the same since we’re on the border. Use your FX Teacher tester to power the board. Once the FX Teacher tester is connected, you can turn the “RATE” knob, the one on the top right. If the LED flashes at different speeds and in red, you’ve got it !We haven’t tested everything, but if you get this result, it’s already a very good indicator. 3rd bag – motherboard voltage reading This table will serve you all along the construction of your pedal. Take your multimeter, put the black wire on a ground wire and the red wire on one of these pins. To help you, the names of the pins are written beside, on both the analog and digital boards. These values may differ by a few % depending on your power supply. Here mine generates 9.40V which you can see on pin S. It’s your turn ! Nom de la pinTensions à vide, carte numérique en boiteTensions avec une carte analogTensions avec une carte analog alluméeA2,47V2,47V2,52VB8,68V8,67V8,62VS9,40V9,40V9,39VH8,85V8,23V8,23VJ-8,84V-8,06V-8,05VL5,01V5,02V5,11VR5,00V5,02V5,10V 3rd bag – jack 3.5mm for the spinner The jack we use is a bit sensitive to heat. Since we have the appropriate soldering irons and we are a little familiar with them, we soldered it for you in the workshop ! Now all you have to do is insert it and solder it on the motherboard as it should be. Wiring of the mini jack, lovingly designed by Damien on his graphics tablet. We don’t need to wire the ground because it will pass through the enclosure, which will also be grounded.Then we look at the jack, wire side, and solder one wire after the other. Example, the left wire goes to the Rx pad of the motherboard. The right wire goes to the T pad of the motherboard. 3rd bag – jacks The jacks go through the motherboard then go directly to the connectors to be finally processed in the daughterboard, 100% analog. How to wire the jacks. Everything is explained in this article : Câbler les jacks de sa pédale For now, all I am asking you to do is prepare the IN and OUT jack with the rest of the wires from the 3rd bag. Don’t solder the red and black from the previous test on the power supply, we have to canning the board first. Once soldered. 4th bag 4th bag BOM. Let’s move on to assembly ! The goal is to insert the motherboard and its peripherals in the enclosure, once this step is over we can move on to the analog board ! 4th bag – spacer To connect motherboard and daughterboard, as you know there are female pins on one side and male pins on the other ! We’re going to reinforce all this with screws and nuts to prevent it from moving in time ! We use the screw on the pot side and the spacer on the chip side. The nut is set aside for later, in order to fix the daughterboard. 4th bag – let’s screw the 3.5mm jack For this step you need a pair of pliers with teeth. This way you can tighten the nut of the 3.5mm jack that you soldered earlier. Insert the mini jack into its hole and tighten the nut. Be careful not to scratch the case ! 4th bag – motherboard canning Come on, let’s follow the video we made for the Ego Driver ! pots mounting. If you have a doubt about the quality of your assembly, don’t put the knobs immediately, it’s not easy to remove them ! The expected result at this step. As a reminder : each pot will have a washer and a nut to install.the toggle switch will only have one nut.and finally, the rotary switch, you don’t put anything on ! it holds itself thanks to the board. 4th bag – power supply wiring Again, this method is presented in our article of effect pedal assembly.The purpose is to supply the pedal with power via the power jack : Heat the legs of the jack enough for the solder to adhere. But be careful not to burn the plastic that holds the legs of the power supply. 4th bag – the footswitches Here, the footswitches used are simple contactors that send information to the microcontroller. Compared to what we find in the article about the true bypass, it’s a close operation of the relay system. Except that it is not based on NE555 but on a microcontroller which controls the relay switching. To simplify your job, the switches are soldered directly on the motherboard, no need to wire them ! On the other hand, if you put the switch on the case, its legs won’t be at the same height as the motherboard pads.So we made wedges for you to screw them at the same height and uniformly ! Wedges for footswitch. So you remove the star shaped nut, unscrew the hexagonal nut a little bit. Then put the wedge under it and tighten the hex nut. Once the 2 footswitches have their nuts at the same height, you screw them to the case with the star nut.You check that the heights are the same and then you just have to solder them ! For soldering you have to heat a little more than usual because the surface is large. Don’t hesitate to put a little more pewter (without abusing it !). Expected result, except that your wires will be a little more orderly, we’ve shortened them since then ! 4th bag – power supply filter As the power supply of the tremolo is rather greedy in inrush current, it is necessary to privilege the capacitive current rather than the inductive current of the transformer. For this we placed 4 or 5 capa of 470uF on the whole pedal ! As there’s never enough you’ll solder one as close as possible to the power supply terminals (there was no more space on the board ^^). For that it’s not complicated, the capa in the 4th bag has a long leg, it will go on the + of the power supply, that is the red wire and therefore the short leg on the black.Before you start soldering, shorten the legs a little so that the capa will stay at the level of the jacks. But be careful not to shorten them too much or you may find it difficult to solder. 4th bag – the jacks All that’s left to do is to screw on the jacks, you start with the washer and then the nut and be careful not to damage/knot the wires ! Expected result once the jacks are screwed in. Once the jacks are screwed in you just have to take care of your wires. You have to make sure that they will never be pinched by the pins, the spacer, the daughter board, the jacks, etc… And make sure they’re close to the motherboard so they don’t hinder it afterwards. 4th bag – canning test For this final test (of the motherboard only, of course !), you connect a 9V negative centered power supply, a jack on the input and the output.Then play with the pots and the switches. If the LED turns white when you switch, the rate changes when you turn the pot, change the subdivisions or even play with the tap tempo. Well all is right in this case ! It works ? Let’s put on the knobs and move on ! You got a little nut left ? It’s normal, we will use it afterwards to hold the analog board ! analog board Now let’s go to the audio part, I promise ! Once again, the whole theoretical part is explained in our blog article. Don’t hesitate to take a look at it before you start soldering, it will allow you to understand all the explanations during the tests. Full analog schematic. This board has also been divided into 4 steps : bypass stagepwm filteringinput bufferthe amplitude modulation The 4 bags of the analog board. 1st bag – the true bypass The purpose of this section is to create a true bypass from a relay. This relay is driven by the ATMEGA328 of the motherboard. This microcontroller turns the relay on and off as many times as necessary, depending on the actions on the footswitch and pots. All these actions are pre-configured by the firmware which took us a few months of development ! True bypass schematic. I and O are connected directly to the input and output jacks via male and female pins soldered to the boards.Likewise, the 9V power supply, the ground and the relay activation are respectively connected through pins B, E and D. 1st bag BOM. 1st bag – reminders Even if you know all types of components, a few reminders won’t hurt ! The article detailing all of this, here. For the transistors, there’s a flat side and a curved side. It’s drawn on the board ! The diode also has a direction, a ring is drawn on one side of the diode, this is the cathode. It is also drawn on the board. The relay has a black stripe on the top, it is also drawn on the board.There are 2 extra pads, we used them before to plug the relay on a socket. But finally it is better without ! 1st bag – male connectors So a little trick to solder the male connectors on the top !The idea is that we want to be able to easily insert the daughter board into the motherboard. For this you will have to solder the male connectors on the component side. You will notice that the connectors have a short side and a long side. We will keep the long side intact so that you can easily insert the board into the female connectors. Then you will have to solder the shorter part on the board. step by step, the assembly of the male connectors. To be well positioned, you put the long part into the female connectors, you insert them slightly but don’t push them in all the way.Then you put your daughter board on the sticking out pins. Once you’ve inserted everything correctly, you push the pins.And finally, you can solder ! 1st bag – tests and measurements insert the daughter board on the mother board. the tensions should be about the same as before.now, since a relay is connected, you can use your pedal on the bypass position. so red led, you have audio passing, white led, no audio.if you are meticulous, you can plug a jack in and out of the pedal to your audio interface. then, check with a frequency sweep that the true bypass does not attenuate certain frequencies.you can also have fun turning the pedal on/off with the bypass footswitch and listen to the relay click. 1st bag – expected result what you’re supposed to get now. 2nd bag – lfo filtering This stage transforms the LFO of the motherboard, which is a PWM signal, into an analog LFO ! LFO filter schematic. About components, there are no traps for this step ! Don’t forget the socket under the chip, read carefully the values of the components and it will be fine. BOM for this 2nd step. 2nd bag – audio tests If you have the FX Teacher tester, you can solder a wire on the TP_LFO pad and watch your LFO on Audacity !Once the wire is soldered, insert the daughterboard on the motherboard via the pins. Then connect the white wire of the tester to the TP_LFO pad and the black wire to the ground of a jack.You don’t need the send (the green and black jack) and you can power the pedal directly from the enclosure. Be careful, the power supply only works by plugging a mono jack in the input jack, even if it’s not connected to anything. Starts Audacity recording and plays with the pedal interface.You should see nice little waves that change frequencies according to the rate ! The setting of the Bias is extremely precise, take the opportunity to put it in sine mode, the pedal instructions are on this page.Then, play with the bias so that the wave is as smooth and curved as possible and that there is no clipping ! Usually when you set it at 2.5/10 it works 99.99% of the time, but you never know ! When you’re done, disconnect the daughterboard and don’t forget to cut the wire on TP_LFO, you don’t need it anymore. 2nd bag – expected result 3rd bag – the input buffer Let’s go to the easiest stage 🙂Its purpose is to make the tremolo as transparent as possible. Without it, you can have impedance problems that can only be solved by putting an OD in front of it, which also needs to be buffered ! Buffer schematic ! In addition, nothing special about components, you can go for it ! The BOM for this step. 3rd bag – tests and measurements We will use the FX Teacher tester to check the transparency of the buffer : connect the output of the audio interface card to the input of the pedal.solder a wire on tp_buff.insert the daughterboard into the motherboard.connect the fx teacher tester, on one side to an input of your audio interface. on the other side, white clip on tp_buff, black clip on the ground of your choice (black wire in the motherboard).connect the 9V power supply to the pedal.go to audacity to launch a frequency sweep, the output spectrogram must be more or less the same as the input spectrogram !disconnect everything and cut the test point wire. 3rd bag – expected result 4th bag – amplitude modulation And finally, the most interesting step, the one that will generate the tremolo effect ! On one side, we receive the buffered guitar signal. On the other, we receive a nice well filtered LFO at the input of the vactrol. Then, we return all this to the amp ! G’ and F are pins connected directly to the volume pot (the first one on the top left), so the work is already done ! Don’t forget to set the GAIN trimpot to 6/10. 4th bag – the optocoupler The only component that changes a bit is of course the vactrol ! The NSL-32 has a dot drawn on it. Same on the board, you just have to refer to it to get the same result. installation of the optocoupler ! 4th bag – expected result 4th bag – tests For this step, the tests are made on the guitar, and yes you’re done ! 🙂Insert the daughterboard into the motherboard, seal it with the remaining nut for the spacer and you’re done ! well done ! Congratulations on that achievement, it wasn’t so easy, was it ? But I think you’ve been helped a bit ! It makes the project much more realizable.If you have any questions or if you have any problems with the realization of the kit, it’s just below in comments. You can also leave sweet words, feedback and even suggestions for the future ! See you soon !