Simple DIY Mixer w/ Op-Amps 

Im still in min 2 and i have to say i havent seen such good class in RU-vid for YEARS!

I learnt how to make a summing mixer when I knew next to nothing about electronics, and have never really thought about how it actually works. Your explanation of the current flowing through the resistors was very good and a bit of an "aha" moment for me. Also the DC offset thing from AC coupled inputs really catches people out. I put together a Eurorack kit (Radio Music) and there is a known issue caused by exactly this which can be solved by soldering an extra resistor between 2 of the components. Great video!

Would have loved to see a crossfader design too ♥️

11:31: The buffer is a voltage follower, a non-inverting unity gain amplifier, with high input impedance (ideally infinite), and low output impedance (ideally zero).

Such great presentation of this concept! Subscribed.

This is literally the Befaco STMIX. 8 minutes in and my eyes have been opened.

This is an absolutely brilliant video. I've always foudn electronics a bit of a struggle and this is so clear

Wonderful pedagogy!! You really answered so many questions i hade! Thank you!

Ty so much for this tutorial and explenation, ill try it asap, i was searching for a op amp based multichannels mixer for alot, ty

Just a great video so clear informative and no fluff

Where have you been all my life! Thank you very much, Excellent.

very good practical tutorial. thanks

Fantastic video, great explanations and interesting comparing designs. Cheers!🥰

Such a good video, learned a heap.

Excellent video! Keep them coming.

well explained and nice demonstration! subbed ;)

Brilliant video, I’m really enjoying all of your great work on the channel! I have a question that I’m hoping you may be able to help me out with. In the context of a synth, you have a number of ac coupled sources at 10vpp (3 oscillators for example). Using a virtual earth mixer with matched resistor values will sum the inputs, resulting in an inverted 30vpp signal. What I cannot get my head around is how people deal with this when only signal is sent to the mixer for example (the other two turned down to using potentiometers as potential dividers). Is the feedback resistor value changed so that the output is 3.3vpp when only one signal is sent to the mixer, then 6.6vpp etc? Or is there something that I’m missing that allows the output to be 10vpp regardless of the number of sources? I hope this makes sense and you can point me to something I may be missing!

Great vid. Your a good teacher thankyou.

Great vid man! Cheers

thank you for this video. awesome channel in general, keep it up!!!

Excellent stuff

Well done 👏. Thanks . When my financial situation improves I will donate . Brilliant explanation.

that's great, I think your workshop shot with the light/bench behind you would benefit from a little extra fill light on the shaded side of your face, you can use some crumpled tinfoil to bounce diffused light for this, the new lights seem to make a real difference :)

There is one exception to the phase doesn't matter rule. Bass transients like drums and percussion instruments. Tweeter phase is interesting.

Thank you for this great video! Regarding the first op-amp curcuit, could you explain why there is any current flowing from the first node after the first resistor eventhough from there on the voltage level is 0 from the negative opamp input side) ? Doesnt that mean that theres no pressure for any current to flow anymore?

Nice tutorial. How to choose quality low noise components?

Great video, thank you so much! As a side project I am tinking about designing a simple small portable (stereo) mixer similar to the 4sum by Syntherjack. But I would like to contro the pots via midi, eg through a teensy. This could be used musically by having a Midi CC LFO for example. Digging into digipots I read that these would introduce glitching sounds when being "turned". Someone suggested using VCAs instead of inverting opamps and digipots. Could you maybe make a video with a VCA based mixer? That would be bomb.

Do you know how to make a quad panner as compared to a stereo panner? Or have any ideas for a simple approach towards mixing to 4 speakers instead of two?

I'm Wonder how many buffers can be used in my modular rack. I was planning on only putting them in all of my oscillator modules, but as I research other module builds, I've noticed that there are options with or without/o buffers (mult/buffered mult, mixer/buffered mixer, etc..). Do I need/should I avoid; running a signal through a buffer on the OSC, through another buffer on the multi, and through another buffer in the mixer, etc? Looking for to the next video🤙

good one

You’re the real life Harry Potter

Can you use this idea for combining multiple oscillators together as like a polyphonic sound? Like if I put 3 sawtooth waves in at 3 different frequencies it would sound like a chord?

All explained so well, thanks! Have yet to build most of your example circuits but have learnt so much from your exposition, really down to earth and clearly explained. Is there somewhere you talk about building dual rail supplies? I've seen so many solutions to this (2x 9V batteries (ugh), using a voltage divider + op amp(low current output?), or use a charge pump built manually (not clean), or a some capacitors and a max1044 chip (maybe this is cleaner than a self built one?), rectify an AC to AC adapter(those adapters seems kind of £££))... As a noob it's all bewildering!

Hello! I am pretty new to this but want to learn. Do you have an absolute basic beginners course just so I can get to grips with the fundamentals? Thanks!

Really? No one? C'mon, it literally GOES TO ELEVEN!

Wytse, its 2999,- and on Thomann. Why the Carbon? Aluminium would have been fine. Is it really as good as Emperical labs or SSL?

Sir isn't 9:06 identical to passive summing? isn't this case the opamp is obsolete?

That was about as close to getting this stuff as I’ve been. Got a bit lost in the closing minutes though with the capacitors and DC offset tho 🤕

hey The AudioPhool, just a quick one: is it possible to power these mixers with a standard sigle rail 9VDC power supply? BTW, keep up the good work!

A-M-A-Z-I-N-G

Why not just have a grounded potentiometer from each input buffer and a single non inverting stage with fixed gain (depending on the number of inputs) - no need for inversion or messing about with gains

no sound for mic input

I have one blutooth module wanted to connect it through wire to two amplifier ...how to do

I don't want to be a nag, but you actually pronounce his name "kurch·haaf".

just got dizz and left this video .....learned nothing here

What a confusing video.