This is my first post ever here yet I’ve been following the forum and Sam’s channels for the past few months.
The crisis allowed me the necessary time to start learn some electronics & I started to build a few diy modules and a cool synth body.
But on the matter at hand. I’m in vacation back in my home country. A friend of mine started the other long trip into synth and music…buying a Minilogue, B. crave, a drummachine and monitor speakers.
Funny enough there is no mixer to put all these together and until next month there will be no possibility for him to get a good one.
I tought of making a simple mixer for him, yet the local electronics store here is very very limited.
As the title says I tought of making the TL072 mixer. Problem is I can’t obtain a +12/-12 power source.
Searching through the internet I found that it might be possible to trick this. Yet my understanding of all of it is still very basic.
It’s not necessarily for me to use a 9v battery. Seen a previous topic in this forum that you would need more V for such a task. If so I do not know how to modify it for a dc power supply.
When using an opamp (such as the TL072), you generally want to have a reference voltage right in the middle of your supply. That’s why it’s easier to use +/-12V supply, as the middle voltage is 0V. But if you want to use a single supply, you just have to create that reference voltage (for example, a 9V supply will need a 4,5V reference). On your first schematic, the two resistances R8 and R9 are dividing the supply voltage by two, creating the needed reference.
The first opamp (IC1A) of that circuit is wired in “Inverting adder”, with a gain of -1. The second stage (IC1B) is a variable gain inverting amplifier with a gain varying between 0 and -2.
The only thing you should take care of when using such low supply voltage is that the maximums input and output levels should be ~2V lower than your supply, or it will distort your signal.
I think C1 is meant as a decoupling capacitor. But there is no decoupling between the inputs. So input-1 is not decoupled from input-2 etc. Should any of the sources connected to an input carrying a DC value, then this will be connected (in part) to the other sources. That may be problematic. In quite a lot of mixers you see that each input has its own decoupling capacitor. Then C1 can be left out.
Yes, but connect it between pin 2 of the jack input and the potentiometer (and leave C1 out). Best is to not use an electrolytic capacitor but an a-polar one.
Hello guys.
Interesting topic for me. I’m working on a Drone Synth based on a 40106 chip and supplied by 9v.
I’m wondering if I would really need an Op-amp output stage or if a passive mixer could do the trick.
There will be one jack output (external mixer, guitar amp, …) and one internal speaker driven by an lm386.
Cheers
and a cool synth body.
