DIY Project #01: Passive Attenuators
Jul 14, 2019 19:50:45 GMT
admin, thetechnobear, and 11 more like this
Post by NightMachines on Jul 14, 2019 19:50:45 GMT
!!! WARNING / DISCLAIMER !!!
Everything you do as a result from reading the following posts, you do so at your own risk. While synth DIY is generally safe, you are working with electricity, hot soldering irons, etc. and those things can be dangerous to your music equipment, house and to your health. Please always concentrate when working on your DIY projects and be calm and careful.
DIY Project #01: Passive Attenuators
Okay, phew … after making your way through the introduction thread, great things await you now, as you are equipped to start your first DIY project.
Attenuators are very useful to scale down CV signals in your modular synth, for example to reduce the effect of an LFO on its target, and they’re easy to build yourself. You actually just need one part: a variable voltage divider, to divide (and thus reduce) the current flow from the source to the target. Yes, we need: Potentiometers!!!
The circuit is super simple
The clockwise (right) leg of the potentiometer receives the input signal, the middle leg is the attenuated output and the counterclockwise (left) leg leads to ground (GND), where the excess current goes.
In this configuration, the potentiometer is turned counterclockwise to reduce the signal. If you switch the left and right legs’ signals, the turning direction is reversed.
First, let’s try it out on the breadboard. But wait! We haven’t actually learned how to use a breadboard yet!
Breadboard basics
The breadboard provides a way to test circuits without the need for soldering. Components can simply be plugged in and out. The board is covered in tiny sockets which are connected in rows and columns, acting just like “multiples” in your AE Modular system. This means that the sockets are copying an input signal to the remaining sockets in the row or column.
Look at this image. The green lines show the usual internal breadboard socket connections:
So when you plug a patch cable with a signal into a socket, the signal comes out of all the other sockets in the same row.
WARNING: Just like your AE Modular multiples, you should not use breadboard sockets to mix signals. There should only ever be one input signal per row, not more. If you plug two or more input signals into the same row, you risk damaging components (or AE modules).
Okay, let’s test our attenuator!
Breadboard Circuit Test
Bill of materials (BOM):
1x 100k Ohm Type B (linear) Pots (AliExpress)
Setup
!!!ATTENTION !!!
Switch off the power to your AE Modular system before you start!
The potentiometers used in the AE Modular system are made to be attached to special PCB mounting holes, which aren’t there on our breadboard. In order to use the pots we need to remove their little side legs. You can either simply bend them outwards with pliers or cut them off with your wire clippers.
Now the three legs of the potentiometers fit nicely into the breadboard sockets.
Each leg is sitting in its own row, so we can use another socket in that row to connect stuff to the legs. Take an AE Modular patch cable and plug it from the left leg’s row into a ground (GND) socket. You can find one on some AE modules, or on a free AE bus connector. Please be very careful to plug it into the correct hole there and not into the +5V port or other sockets.
Now that we have established the ground connection, plug another patch cable from the pot’s middle leg into a Mixer module input. And finally, patch a VCO signal to the right potentiometer leg.
The patch should look like this:
!!! ATTENTION !!!
Double-check your patch cables now! You will switch on the power to the system next. This means that your DIY circuit is connected to your modular synth and if you made a mistake, things might break. After powering your system on, immediately check if all things look normal. If you feel something is behaving weirdly (e.g. no LEDs light up, no sound, weird smell) disconnect the power immediately and re-check your cabling.
Now, turn on the power to your AE Modular system and listen to the mixer module output on speakers. When you turn the potentiometer on the breadboard, you should hear the volume change.
Congratulations! You just built your first synth DIY circuit!
LFO Attenuation Test
Now, instead of the VCO signal, patch an LFO output to the right potentiometer leg and patch the middle leg to a modulation source, like a filter cutoff CV input.
Patch a VCO through that Filter to the Mixer and listen how the LFO effect decreases when you turn the potentiometer counterclockwise. Awesome!
Constant CV Source Test
One more experiment! Keep the filter modulation patch from before, but instead of the LFO, connect the right pot leg to a +5V socket on the AE Modular (either on a module or on the power bus connector).
Now, the pot will act as a static control voltage supply, which lets you modulate the filter cutoff manually. Of course there is already such a knob on the filter module itself, but now you know that you can use the +5V from the power bus as a control voltage too.
What next?
So this all seems to work great! Next you could try to add some more potentiometers to your breadboard and duplicate their circuits. Since they will all share the GND connection on their left legs, you can use another row on your breadboard to "multiply" the one GND signal you already patched:
Once you feel comfortable with all of this. You can take the parts off the breadboard, solder them onto a PCB and build your own AE Modular attenuator module. In fact, this is what I will show you next in this thread. So stay tuned
Everything you do as a result from reading the following posts, you do so at your own risk. While synth DIY is generally safe, you are working with electricity, hot soldering irons, etc. and those things can be dangerous to your music equipment, house and to your health. Please always concentrate when working on your DIY projects and be calm and careful.
DIY Project #01: Passive Attenuators
Okay, phew … after making your way through the introduction thread, great things await you now, as you are equipped to start your first DIY project.
Attenuators are very useful to scale down CV signals in your modular synth, for example to reduce the effect of an LFO on its target, and they’re easy to build yourself. You actually just need one part: a variable voltage divider, to divide (and thus reduce) the current flow from the source to the target. Yes, we need: Potentiometers!!!
The circuit is super simple
The clockwise (right) leg of the potentiometer receives the input signal, the middle leg is the attenuated output and the counterclockwise (left) leg leads to ground (GND), where the excess current goes.In this configuration, the potentiometer is turned counterclockwise to reduce the signal. If you switch the left and right legs’ signals, the turning direction is reversed.
First, let’s try it out on the breadboard. But wait! We haven’t actually learned how to use a breadboard yet!
Breadboard basics
The breadboard provides a way to test circuits without the need for soldering. Components can simply be plugged in and out. The board is covered in tiny sockets which are connected in rows and columns, acting just like “multiples” in your AE Modular system. This means that the sockets are copying an input signal to the remaining sockets in the row or column.
Look at this image. The green lines show the usual internal breadboard socket connections:
So when you plug a patch cable with a signal into a socket, the signal comes out of all the other sockets in the same row.
WARNING: Just like your AE Modular multiples, you should not use breadboard sockets to mix signals. There should only ever be one input signal per row, not more. If you plug two or more input signals into the same row, you risk damaging components (or AE modules).
Okay, let’s test our attenuator!
Breadboard Circuit Test
Bill of materials (BOM):
1x 100k Ohm Type B (linear) Pots (AliExpress)
Setup
!!!ATTENTION !!!
Switch off the power to your AE Modular system before you start!
The potentiometers used in the AE Modular system are made to be attached to special PCB mounting holes, which aren’t there on our breadboard. In order to use the pots we need to remove their little side legs. You can either simply bend them outwards with pliers or cut them off with your wire clippers.
Now the three legs of the potentiometers fit nicely into the breadboard sockets.
Each leg is sitting in its own row, so we can use another socket in that row to connect stuff to the legs. Take an AE Modular patch cable and plug it from the left leg’s row into a ground (GND) socket. You can find one on some AE modules, or on a free AE bus connector. Please be very careful to plug it into the correct hole there and not into the +5V port or other sockets.
Now that we have established the ground connection, plug another patch cable from the pot’s middle leg into a Mixer module input. And finally, patch a VCO signal to the right potentiometer leg.
The patch should look like this:
!!! ATTENTION !!!
Double-check your patch cables now! You will switch on the power to the system next. This means that your DIY circuit is connected to your modular synth and if you made a mistake, things might break. After powering your system on, immediately check if all things look normal. If you feel something is behaving weirdly (e.g. no LEDs light up, no sound, weird smell) disconnect the power immediately and re-check your cabling.
Now, turn on the power to your AE Modular system and listen to the mixer module output on speakers. When you turn the potentiometer on the breadboard, you should hear the volume change.
Congratulations! You just built your first synth DIY circuit!
LFO Attenuation Test
Now, instead of the VCO signal, patch an LFO output to the right potentiometer leg and patch the middle leg to a modulation source, like a filter cutoff CV input.
Patch a VCO through that Filter to the Mixer and listen how the LFO effect decreases when you turn the potentiometer counterclockwise. Awesome!
Constant CV Source Test
One more experiment! Keep the filter modulation patch from before, but instead of the LFO, connect the right pot leg to a +5V socket on the AE Modular (either on a module or on the power bus connector).
Now, the pot will act as a static control voltage supply, which lets you modulate the filter cutoff manually. Of course there is already such a knob on the filter module itself, but now you know that you can use the +5V from the power bus as a control voltage too.
What next?
So this all seems to work great! Next you could try to add some more potentiometers to your breadboard and duplicate their circuits. Since they will all share the GND connection on their left legs, you can use another row on your breadboard to "multiply" the one GND signal you already patched:
Once you feel comfortable with all of this. You can take the parts off the breadboard, solder them onto a PCB and build your own AE Modular attenuator module. In fact, this is what I will show you next in this thread. So stay tuned
