Simple DIY Mixer w/ Op-Amps

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2 жыл бұрын

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Today we're going to apply what we've learned about op-amps to make a simple summing mixer. This allows us to mix multiple signals to a single output channel, using nothing more than a few op-amps and a handful of resistors! We'll see how we can do this with an inverting or non-inverting configuration and the advantages or disadvantages each.
Schematics here!
Inverting Config: drive.google.com/file/d/1E3bx...
Non-Inverting Config: drive.google.com/file/d/1Hf_N...

Пікірлер: 76

@jcmerlob746 3 ай бұрын

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

@StephenBrown85 2 жыл бұрын

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!

@TheAudioPhool 2 жыл бұрын

Yeah it's an absolute classic. I think all of us as beginners get a bit 'capacitor happy'. When i wasn't sure why my circuits weren't working i would just start chucking capacitors in everywhere and probably made everything worse! haha :)

@johnno31uk 2 жыл бұрын

I had the same aha moment. Thanks for the great explanations. Add input panning and stereo summing in a future video perhaps? Great reference I’ve found for mixer theory: sound-au.com/project30.htm (and there’s also a deep analysis of balanced interfaces if you want to go down the rabbit hole further)

@DJDiskmachine 9 ай бұрын

Would have loved to see a crossfader design too ♥️

@foureyedchick 2 жыл бұрын

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).

@deryckschnee6376 Ай бұрын

Such great presentation of this concept! Subscribed.

@jakobmathiszig-lee8046 Жыл бұрын

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

@maxasken 11 ай бұрын

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

@JKEYSONVINYL 8 ай бұрын

Just a great video so clear informative and no fluff

@GM-qz9fo 6 ай бұрын

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

@giova___0232 2 жыл бұрын

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

@DJDiskmachine 9 ай бұрын

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

@Peter12662 2 жыл бұрын

Excellent video! Keep them coming.

@TheAudioPhool 2 жыл бұрын

Trying to stick to a rhythm of posting every other week or better! Thanks for watching :)

@user-ie6de8xe2f Ай бұрын

very good practical tutorial. thanks

@alexreeve 2 жыл бұрын

well explained and nice demonstration! subbed ;)

@danieleden1856 2 ай бұрын

Such a good video, learned a heap.

@jamesdix922 2 жыл бұрын

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!

@timb.4825 Жыл бұрын

Great vid. Your a good teacher thankyou.

@angelos808 2 жыл бұрын

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

@TheAudioPhool 2 жыл бұрын

Thanks for watching! :)

@adastra123 2 жыл бұрын

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

@TheAudioPhool 2 жыл бұрын

That's so kind of you. Don't put yourself in any financial hardship!!

@TheDivergentDrummer 6 ай бұрын

Great vid man! Cheers

@ofootyeabicc201 Жыл бұрын

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

@TheAudioPhool Жыл бұрын

Exactly! It almost feels like cheating once you understand the fundamentals :)

@adamarmfield1069 2 жыл бұрын

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 :)

@TheAudioPhool 2 жыл бұрын

Thanks! Ill have a go next time. The camerawork and lighting stuff is a constant work in progress. Appreciate the tips and thanks for watching :)

@adamarmfield1069 2 жыл бұрын

@@TheAudioPhool that's alright, i got some bridgelux cobs i haven't done anything with yet, they need a decent heatsink that isn't easily available in the uk, rs had them for about £3, they're 95cri so pretty decent

@nigelpearson6664 6 ай бұрын

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

@tientienyao 3 ай бұрын

Nice tutorial. How to choose quality low noise components?

@asadlalani9057 Жыл бұрын

Excellent stuff

@beatnikcafe 6 ай бұрын

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?

@quinxx12 2 жыл бұрын

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?

@martinmartinmartin2996 8 ай бұрын

You must re study the inverting operational amplifier! the voltage at the inputs to the is incorrectly marked as 0 , this voltage turns out to be very, very small when the operational amp is operated the voltage at the junction of R1and R2 is often called ε = Vin/Aol. example in =1v ; A]open loop = 100,000 to 1,000,000 so ε = 10uv to 1 uv !

@jaysilence3314 2 жыл бұрын

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.

@TheAudioPhool 2 жыл бұрын

It's on my list! Thanks for watching :)

@jaysilence3314 2 жыл бұрын

@@TheAudioPhool Can't wait! In the synth forums there is a demand for a small mixer, preferably with multi track audio interface capability. Everybody likes the TE TX-6 device but also everyone tinks ist is way way too expensive. A Open Hardware DIY mixer would be awesome.

@phyphedelic3214 2 жыл бұрын

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🤙

@TheAudioPhool 2 жыл бұрын

Having more buffers can't really hurt, the only thing is as you've figured out is that they draw current. It's good to know when you can get away with using as few op-amps as you can as i started to get into this video, one easy thing to do is build up/simulate your designs and just see how much current they draw. It all depends on your power supply what you can handle. You can always add another psu! (video on that coming soon)

@phyphedelic3214 2 жыл бұрын

@@TheAudioPhool that makes sense. On one hand, I didn't understand the need to run a buffered signal through a buffer; however, I was also afraid that running a signal through an unbuffered module would degrade the signal more than the initial buffer could support. This is good news since I've already built my multi's and mixer unbuffered

@twobob 2 жыл бұрын

good one

@DirkArnez 5 ай бұрын

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

@LabSkaterPussies 2 жыл бұрын

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?

@TheAudioPhool 2 жыл бұрын

Absolutely! This is basically how a polyphonic analog synthesiser works. You have one oscillator & vca per 'voice' (basically note) and then you mix them all together

@LabSkaterPussies 2 жыл бұрын

One follow-up question, if you were to mix say 3 sawtooth waves together, wouldn't the output signal be louder than the inputs since the peaks might be added together at some points? If you increased to 8 inputs, wouldn't the output just get louder? Even if they are all different frequencies? When making a polyphonic sound do you just have to manually control the volume of the output based on what you are putting in?

@cdgonepotatoes4219 8 ай бұрын

@@LabSkaterPussiesat a certain point the signals will simply peak to the amplifiers max output voltage. I assume you may get a chord with three distinct sounds if you directly pass the output through a speaker because the offsets may be slightly different? And the amplifier in this configuration can work as an attenuator or you could hook the output to a compressor.

@gdrdm Жыл бұрын

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!

@TheAudioPhool Жыл бұрын

Sorry only just seen this. If you go under my channel I have a "synth from scratch" playlist that goes from some very simple circuits, through basic circuit theory up to where we are now. Let me know if there's anything specific you want to know more about!

@gdrdm Жыл бұрын

@@TheAudioPhool Thank you! I'll check it out. Appreciate the videos and the time to reply! Cheers

@TheAudioPhool Жыл бұрын

@@gdrdm Appreciate the comments. Good luck on your electronics quest!

@paulconnell5399 2 жыл бұрын

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 🤕

@TheAudioPhool 2 жыл бұрын

Just make sure if you use a capacitor on the input of an op-amp you put a big (100k+) resistor from the op-amp input down to ground. :) It gives any small currents a path to flow that doesn't go through the capacitor, because you don't want to accidentally charge that capacitor up for the reason i showed on the scope! I have a 3 part series on capacitors if you want to know a bit more: kzfaq.info/get/bejne/es6ol8tnvJjSZ3k.html Thanks for the kind words!

@paulconnell5399 2 жыл бұрын

@@TheAudioPhool that’s my evening viewing taken care of. Cheers.

@oscarmoralesjuarez2274 Жыл бұрын

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

@thengel24235 2 жыл бұрын

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!

@TheAudioPhool 2 жыл бұрын

Thanks!! you're too kind :) Yeah it is a real pain. The worst thing as a beginner! Building a proper +-12v supply video coming very soon!

@thengel24235 2 жыл бұрын

@@TheAudioPhool I had another quick question actually, do you think you could point to some resources/ explain briefly what is meant by output/input impedance in this context? Having a hard time understanding this!

@majordabalert Жыл бұрын

You’re the real life Harry Potter

@kevindewinter8235 Ай бұрын

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

@lorenzobiagi5200 Жыл бұрын

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!

@TheAudioPhool Жыл бұрын

Yes. Basically replace any -v with gnd, and then any gnd with 4.5v :)

@lorenzobiagi5200 Жыл бұрын

@@TheAudioPhool oh thank you very much! this makes things much easier for me (for some reason I don't get the meaning/need of dual power supply). awesome! let's build it! cheers

@lorenzobiagi5200 Жыл бұрын

@@TheAudioPhool hi, one more on this topic: where do usual GND connections such as the metallic shell of pots or the ground leg of the output jack need to be connected? do those terminals go to GND (as usual) or to 4,5V? Thank you!

@HeywoodJablomie Жыл бұрын

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

@malcolmhodgson7540 Ай бұрын

Is there only us who got that?

@RavenLuni Жыл бұрын

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

@cdgonepotatoes4219 8 ай бұрын

I meant to reply by saying the math is different and the output wouldn't be the same with variable inputs unless you keep adjusting the potentiometers, but I tried to produce some examples off the top of my head and it was. Could be my math was wrong but still... Without pen and paper in hand, my first answer would be "you may not care about the inversion say with sound unless you want to further process the signal." I may come back to this later. EDIT: still haven't tried myself, but reading on this it seems that it all comes to the noise of that +1 you get in the non-inverting configuration. When it matters that the output signal is in phase, it's more convenient to just use a second inverter. You can also do sub-volt addition, whereas you can't if you have a static voltage of 1 without inverting your inputs.