Thank you so much for these videos! I'm currently trying to teach myself circuit design for some module ideas I have kicking around, and the way you step through these circuits is amazingly educational.
Really well-explained video, thanks. I came here after looking at the schematic because I never saw electrolytic capacitors back-to-back like that before... Is this purely to get a "large" value of cap that's effectively non-polarised? Could they be replaced with a single 4.7uF or 10uF ceramic cap? (I have about 50 of each sitting here!)
Yup you can certainly use a larger single cap. For audio coupling applications using normal polarized caps is the most common since usually large voltages don't develop across them in both directions. (you're usually putting on or taking off a DC offset) But for a circuit like this you want to store either polarity of voltage.
Great vid! I'm trying to build my own modular synth, and your videos have been a great help to a beginner like me! However, could someone help me understand -12v? Why not just use ground?
It's a seemingly simple question with a complicated answer. Firstly, audio (and usually control) signals are often signals that vary up and down around a centre point. When there is no sound, the output is 0 volts. Most sounds are represented by vibrations that go positive as well as negative. (this happens in the real world too) So to deal with those in electronics we normally need to be able to make signals of both polarities. So we treat 0V as the centre, and set up our circuits to allow both positive and negative voltages. (with respect to this 0V signal, or ground) The other part has to do with how most audio circuits are designed. The common component for modern audio and synth circuits is the op amp. Most op amps expect signals somewhere in between its power supply pins. Due to limitations in their design the signals can't go all the way to the power supply rails. So it's often convenient to power an op amp from, say, +12 and -12 and then deal with signal of maybe +/-5V or +/-10V. When the range of signals you want to deal with are well within the range of the power supply voltage rails, everything gets easier. Of course there are exceptions and many low voltage designs (mobile phones, laptops, etc.) use a single power supply for audio circuits. But this has limitations and annoyances. Because most synth circuits are DC coupled so they work way down into super low frequencies, a dual-rail power supply is always more convenient, despite seemingly more complex and annoying to implement. I'll do a full video about this sometime but I hope that helps to shed some light on it.
If I use a 100K pot instead of the 250K I just get a shorter max slew rate, right? I don't have any 250k pots on hand and I'm just wonder if it is worth getting them if I don't need super slow slew rates.
shiftedphase well, I'm in my second year of electronics engineering and it's really interesting to watch your videos. All though, I'm not at your level yet aha
Thank you so much for these videos! I'm currently trying to teach myself circuit design for some module ideas I have kicking around, and the way you step through these circuits is amazingly educational.
Really well-explained video, thanks. I came here after looking at the schematic because I never saw electrolytic capacitors back-to-back like that before... Is this purely to get a "large" value of cap that's effectively non-polarised? Could they be replaced with a single 4.7uF or 10uF ceramic cap? (I have about 50 of each sitting here!)
Yup you can certainly use a larger single cap. For audio coupling applications using normal polarized caps is the most common since usually large voltages don't develop across them in both directions. (you're usually putting on or taking off a DC offset) But for a circuit like this you want to store either polarity of voltage.
Great vid! I'm trying to build my own modular synth, and your videos have been a great help to a beginner like me! However, could someone help me understand -12v? Why not just use ground?
It's a seemingly simple question with a complicated answer.
Firstly, audio (and usually control) signals are often signals that vary up and down around a centre point. When there is no sound, the output is 0 volts. Most sounds are represented by vibrations that go positive as well as negative. (this happens in the real world too) So to deal with those in electronics we normally need to be able to make signals of both polarities. So we treat 0V as the centre, and set up our circuits to allow both positive and negative voltages. (with respect to this 0V signal, or ground)
The other part has to do with how most audio circuits are designed. The common component for modern audio and synth circuits is the op amp. Most op amps expect signals somewhere in between its power supply pins. Due to limitations in their design the signals can't go all the way to the power supply rails. So it's often convenient to power an op amp from, say, +12 and -12 and then deal with signal of maybe +/-5V or +/-10V. When the range of signals you want to deal with are well within the range of the power supply voltage rails, everything gets easier.
Of course there are exceptions and many low voltage designs (mobile phones, laptops, etc.) use a single power supply for audio circuits. But this has limitations and annoyances. Because most synth circuits are DC coupled so they work way down into super low frequencies, a dual-rail power supply is always more convenient, despite seemingly more complex and annoying to implement. I'll do a full video about this sometime but I hope that helps to shed some light on it.
Shiftedphase Thanks so much! Totally useful reply!
Thanks so much! Very helpful!
If I use a 100K pot instead of the 250K I just get a shorter max slew rate, right? I don't have any 250k pots on hand and I'm just wonder if it is worth getting them if I don't need super slow slew rates.
Yup that's right! Try a few and see which one works for you. You can also add extra resistance in series or parallel to change the range.
Are you an electronics engineer?
shiftedphase well, I'm in my second year of electronics engineering and it's really interesting to watch your videos. All though, I'm not at your level yet aha