There are plenty of audio mixers on the market, and the vast majority all look the same. If you wanted something different, or just a nice learning experience, you could craft your own instead. That’s precisely what [Something Physical] did.
The build was inspired by an earlier 3-channel mixer designed by [Moritz Klein]. This project stretches to eight channels, which is nice, because somehow it feels right that a mixer’s total channels always land on a multiple of four. As you might expect, the internals are fairly straightforward—it’s just about lacing together all the separate op-amp gain stages, pots, and jacks, as well as a power LED so you can tell when it’s switched on. It’s all wrapped up in a slant-faced wooden box with an aluminum face plate and Dymo labels. Old-school, functional, and fit for purpose.
It’s a simple build, but a satisfying one; there’s something beautiful about recording on audio gear you’ve hewn yourself. Once you’ve built your mixer, you might like to experiment in the weird world of no-input mixing. Video after the break.
This is a fun project! The enclosure is beautiful. Meters would be nice; maybe on the next iteration. But if I’m not bitchin’ I’m not breathin’.
Again, maybe on a later iteration: sliders provide an unpowered graphical presentation of quantitative information (hat tip Mr. Tufte).
All-caps Dymo? You say retro, I say cheezy. and this native English reader finds them barely legible, they need to be flipped around so the “P” in “PIANO” is at the top where the “O” is in the photo. The industry standard is that English reads right to left, top to bottom. Custom refrigerator magnets would be one solution; for cheap use existing refrigerator magnets, a *grown-up” label maker and an X-Acto knife.
That said, two thumbs up! If I had stuff to mix and didn’t already have an 8 track digital recorder this would fit my low level of expertise and be a doable project.
Magnets on alu?
I wasn’t consulted on the materials list. If alumibum is absolutely necessary for looks, thin sheet appluminOS over steel. Wow, I’m exhausted after coming up with that hack. Oh wait! Here comes another one: in-case neodymium magnets. So strenuous, must power down.
Don’t you mean left to right? I think that’s what you meant.
I agree that all-caps makes reading harder, but that’s a minor point and maybe comes down to personal preference. For a setup like this, having color-coded tape on the cables, matching dot or donut stickers on the enclosure could be a good visual approach to keep track of things.
Yes dammit! I screwed the pooch on that one, thank you. Forget reading, all-caps just looks crappier (personal taste); the hard-to-read part comes from the orientation. “color-coded tape on the cables”? What is this hatred (hat red) for color blind people? How about word-coded tape on the cables? A cable label if you will, and you will.
Ok, how about we negotiate for a middle ground and go with word-coded labels on color-coded tape? That way anyone can see them from close range and the color-differentiating folks can see that everything is right from across the room.
Funny story, as a gift in middle school I received a ream of neon paper, I think 100 sheets each of five different colors. For years I had no idea what to do with it, but held onto it since it was a gift from relatives. Around my first year of engineering school, I started printing cover sheets for homework problem sets onto sheets of neon paper. On occasions when the professor would return the graded homework by setting it on a table at the corner of the lecture hall, looking for the neon cover sheet among the sea of white papers saved me a lot of time.
Back to the mixer project, a meaningful improvement (in my opinion) would be to put the audio cable receptacles on the front face rather than the top. Assembly becomes more challenging but the user experience could be so much better.
If you’re “across the room” you have no reason to be looking at the board. Like what you say about audio cables and where they get jammed in but I suspect the industry standard is for good reasons to jam your male plug into the rear. Keep the cables out of way: don’t accidently disconnect none with your foot or bong, won’t be none. The potentiometer knobs/spindles are perhaps the least well executed part of the project: if you insist on knobs/spindles at least throw some some Telecaster knobs or numbered knobs (Tufte again on that thang!
Interesting, I always thought neon was inert, never heard of it in the paper industry. In my 4th ill-spent year in college I handed in my final Islamic Theology paper with no name or other indices of identification other than the subject I chose. Got me one of them A’s you hear tell of.
Better not walk into a French library (or German, or Spanish…). Your head will explode.
As Fiddler said to Kunta Kinte “You in America now bwoy!” Of course you may not be but you get the point. I’m not the one who chose English for the labels, just playing the hand I was dealt. Note the ON-OFF label. Jarring to this viewer.
Wow, so you feel like you most closely align with the idea that slaves (and voluntary immigrants) should give up their identity. (Also, I’m sure you’ve been waiting YEARS to use “boy” on someone). Nobody cares bro
Oh dude, you a raciss! It’s a well known quote from a world famous TV show, Alex Haley’s Roots.
“Kunta Kinte: What’s snow, Fiddler?
Fiddler: Never you mind, boy, never you mind. Let’s get on back to home. I got enough trouble teaching you the difference between manure and massa. ‘Course there ain’t all that much difference when you gets right down to it.”
If you so raciss that you don’ know Roots I can’t help you (and this time I’m spelling it right) m’bwoy.
“Also, I’m sure you’ve been waiting YEARS to use “boy” on someone” Godfrey Daniels you are full of hate! What the hash browns is wrong with you? Is this a new derangement or ongoing?
Louis Gossett Jr. from Officer and a Gentleman and Iron Eagle and Lavar Burton from Star Trek TNG and Reading Rainbow played the scene. Take your mental problem up with those two colored fellas.
On my personal scale for ranking people you tested out as SFI level. I’m being civil so what that means is left as an exercise. Okay, in the spirit of good fellowship I’m going full remedial: “exercise” is when someone tries do stuff. Surely you’ve seen it? Thanks for the input but no thanks, not even after last call at The White Swallow. Massa.
I would argue that it’s not an active mixer, but rather a passive mixer with a buffer on the output. And as far as I can tell, adjusting the level of one input will also change the levels on all the other channels. That’s generally considered to be a bad thing in an audio mixer.
I think that adding eight op-amps – one on the wiper of each channel pot – would result in a better design. It would increase the noise a little bit, but quieter amps would mitigate that.
Correct in principle, but here the summing point is at ground potential, held there by the first opamp. Adjusting any input won’t change that voltage, so won’t propagate to other channels.
But buffering lets you do other things more easily, like panning and equalization and adding a preamp.
It also reduces cross talk between channels. Slapping a non-inverting buffer on each channel however quadruples the number of needed op-amps (or just use a quad op-amp, that’s only two additional chips to mount). Digikey tells me the used op-amp less than 2€ a piece, so another 8€ for the op-amps plus a few cents for the filter caps. Simple enough. Years spent in a lab told me to always buffer inputs and outputs…
The mixer should also limit the resulting signal to maximum line level, shouldn’t it? At +/-9V symmetric supply this is waaay high, isn’t it? (I think it should be about +/-1.5V for line?).
I like buffering everything too – but you have to be careful about noise. Even with decently quiet op-amps like the NE553x series, the hiss can get objectionable fairly quickly if you don’t keep on top of it. That’s not too hard if you’re designing at the system level, but if you’re doing it piecemeal it can be a problem.
Thanks for the correction. I thought of the summing-point-as-ground point when I was writing my comment; but I had a brain fart and convinced myself that it was a high-impedance point. I just looked at the schematic again now and suddenly it was obvious. Perils of an aging brain I guess…
“Nice that the number of channels land on a multiple of four?” Not a power of two? I know eight is both, but since I don’t come from much of an audio recording world I was wondering why the multiple of four is important rather than power of two, sounds like an interesting story
There are no non-negative multiples of or powers of four that are not multiples of or powers of two. But having seen you raise the question I have the same qualm. Perhaps the writer started out on a four-track as many people such as myself but not the Beatles do/did? Beware: I probably got something wrong here too.
https://www.beatlesbible.com/forum/recording-and-musicology/recording-with-two-track/
Permit me to give the writer full marks for saying “multiples of four” rather than “powers of four” because 24 track recorders/mixers/boards are not uncommon.
Good props, Author!
Drill pilot holes
Don’t cut the anti-rotation tabs off the pots
Nothing wrong with learning. If this was tipped up to sit on the rear it would make more sense. Jacks at the top, cables out of the way just like pro mixers. The way it is the pots without knobs are hidden behind a forest of adapted to tall plugs, and too close for sizable pointer knobs. It should be from front to rear, knob, label, then jacks. Your fingers shouldn’t cover the labels whilst lingering with perhaps both hands on knobs.
Of course the pointers should go from 7 o’clock minimum to 5 o’clock max (12 hour face), which is standard. I’ve a Yamaha board with gear rack and pinion “sliders” on rotary pots (highest quality sealed), but all the EQ and monitor pots labels go from 11 o’clock max to 1 o’clock minimum! At least they are clockwise increase. Weird! I guess they wanted to see the center setting and pointer than be hidden behind the knob.
The project by Moritz isn’t showing up. It’s a duplicate link of rhe Something Physical video.
For those few actually stumped by that error: https://www.youtube.com/watch?v=q8tmUgaXrEQ
Nice build, though it lacks some creature comforts like meters and faders. I am currently building a 16 channel unit with 3 band parametric EQ, meters and faders. I hope to put it into a nice case and have it in my recording setup. Yeah, I could buy a cheap mixer at the music store, but this is a hell of a lot more fun, and will probably have better quality than the cheap ones I could buy, and cost about the same.
Q: Will each channel have its own EQ? Otherwise why build it in? Are “faders” the same as slide potentiometers?
Yes. Each channel has a parametric EQ, and the “faders” are slide potentiometers.
My brother built a mixing console for a studio he and a couple of friends started back in the late 60’s.
You can see what it looked liked here:
https://buckeyebeat.com/landenrec.html
He also worked for legendary mixing console maker Flickinger, and installed them in several studios in the states, one for Johnny Cash’s home studio. He also worked as Cinderella Sound in Tennessee, and had recently restored the Flickinger there, as the owner was retiring and sold the unit to a studio in Germany.
“He also worked as Cinderella Sound in Tennessee” That was your brother? Now I feel kind of weird but say “Hi!” for me.
Sounds cool, but seeing as it’s just yet another YouTube link, I’ll never know.