Designing a simple audio compressor from scratch
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- čas přidán 19. 06. 2024
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In this episode, we'll DIY our way towards a simple audio compressor circuit, based on my diode VCA. If you want to build along, here's the bill of materials:
1x TL074 quad op amp
1x TL072 dual op amp
11x 1N4148 small signal diode
1x 10 uF capacitor
1x 100k log potentiometer
2x 100k lin potentiometer
1x 20k lin potentiometer
10x 100k resistor
2x 20k resistor
2x 14k resistor
1x 4k7 resistor
1x 1k resistor
Chapters
00:00 Intro & what is compression?
04:21 Rough circuit structure
06:12 Diode VCA
09:48 Peak detector
14:19 Voltage subtractor
16:24 The gap & how to get rid of it
21:34 The ratio control
23:32 Attack & release
27:45 Sidechaining & outro - Věda a technologie
The extra effort here with the animations was definitely appreciated on my end! I love that you slipped a side chain feature in at the very end! Beautiful stuff Mortiz!
glad to hear - doing the animations is super fun, will definitely expand on this in the future.
@@MoritzKlein0 Agreed. This new approach is really well done and looks great. Thanks for the awesome content!
@@MoritzKlein0 what did you use for those animations? They’re super helpful.
@@MoritzKlein0 Animation helped me a lot here thanks
animations super helped
I am a hobbyist C++ Audio DSP programmer, so I understand exactly what a compressor does and the functional blocks used to control it, but the actual breakdown of specific implementations using electronic components has always eluded me.
Looking at electronic circuits without experience made it difficult to see the "boundaries" between components. Your video has helped me realize that obtaining generalized knowledge of common audio electronics sub-assemblies and the ability to identify those sub-assemblies is the key to my understanding audio electronics in general.
I feel significantly less intimidated about designing audio circuits after watching this video. Thank you so much for the work that you do!
Yeah, thinking in modules i guess. It's what makes any tear down or circuit analysis video good, is them kind of circling part of the board and saying what it is and then the individual components, and it's the right way to think of circuits. I guess the only difference is when you don't know and see a circuit board it looks over overwhelming but if you can break it down into its parts or sections it's more approachable.
I hacked a Yamaha compressor GC2020 to have a 10-second release time, it was so that when I watched a movie the sound was absolutely perfect and without it going beyond the dynamics and when the scenes with low volume the compressor slowly turned up the volume. Attack time=0, Release time=10sec or less
I'm in a similar boat designing a pi DSP drum machine+synth. Care to share your favorite resources of getting to understand compressors? This video helps but im trying to soak up some more. Thanks!!
Yeah, that's what engineers (have to) do... Divide and conquer. Doesn't matter if it's HW or SW. chop it into simple modules and test them thoroughly
Ive taken the full electronics series of courses in my degree track. Stumbling across these videos makes everything I've learned click.
As a pedal designer, compressors have always puzzled me. This is a very nicely done video describing how they work. Thanks
i don't work in music any more but one of my favorite things is asking "pedal designers" simple things like "what does an NPN transistor do" and "how does ground work"?
@@chrismathewsjr lmaoo how does it go then
@@executorarktanis2323 I am more basic. I would first ask why he uses his assumptions(or delusions?) on his hypothetical designers with an example in the style of the Brothers Grimm? What stupid (and the totally unnecessary blanket insulting taunt) stuff he's talking up there? A totally insane straw man about how transistors work... thrown out of context to make himself important. Great! Now we all know the kind of people he dislikes: music pedal designers. Did someone ask for that? Or does this childish BS interest anyone? As @elluisito000 said, it is a very interesting topic. Just search for "boss compressor schematic" or "Formant", "Parametric Multiband", "Hollis", "Teletronix", and so on. Not a bad idea to learn from the experts ... or ancients ... or ancient experts!:) Have fun playing and soldering, all (including our braggart).
@@dieSpinnt holy thanks man
@@chrismathewsjr I'm not an obstinate prick anymore, but one of my favourite things is asking guys like this simple things like "how do you talk to people at parties without them all leaving"?
i have been looking for a good compressor circuit that didn't need any fancy components (monolithic VCA chips, OTAs, special FETs , or LDR tuning) for a long time and finally here one is.
You should modify the peak detector to use a precision rectifier instead of a half wave single diode like you use. That way you can reuse the circuit for an envelope detector to control a VCF without noticeable wobble when playing bass frequencies. The big downside to half wave peak detectors like that is that with bass frequencies you tend to hear a lot of wobble in the envelope as it’s only acting on half the peaks.
This works great for symmetric wave forms, which is most of the cases.
Now, imagine you have a wave form which has negative peaks and no positive peaks, then the peak detector will never turn on.
To solve this problem you need to place absolute value circuit before the peak detector, which could be as simple as full wave 4 diode rectifier circuit or its opamp equivalent.
I just built this circuit with some changes for my guitar. Since unamplified guitar voltages are a few hundred mV at most, I only used one diode on each side of the diode bridge and didn't attenuate the signal going through it. Other than that, I replaced the potentiometers with fixed resistors since I don't have any pots on-hand and changed two or three resistor values, but that's it. It works really great as a compressor.
hey, I'm trying to recreate this circuit for the same purpose as you, for a electronics class in college, I would very much appreciate if you could share the components you used, specially the OpAmp, since all the OpAmp I own strugles with such low voltages. Thank you.
I have been on the audio scene for over thirty years, I mean on the electronics field rather than in the use of the machines, and believe me...I have never found a book or document that explains in both easy and comprehensive way the subject you have gift us on this video. Not only the practical design and the theory behind (without getting into heavy design issues) but, also, the perfect animation and perfectly chained explanation. I have subscribed immediately to your channel. Thank you for your work.
This is exactly, how to learn analog circuit design. I absolutely love how you describe every single detail. That shows that you truly understand what you are doing, making it really really helpful for others to understand these concepts. So helpful, thank you so much.
This single video is more useful than any of my circuits classes ever were
2:02 - My god. This is the best explanation of compression I have ever seen
This is the best stuff about electrotechnical principles in music. This beats all that I've learned for several years in my engineering university. Just excellent and very inspiring! Thank you!
Agreed awesome stuff
I’m not sure how I haven’t had your videos in my recommended yet but I’m genuinely excited to have found your channel
i've been wanting to learn about signal processing, and electronics in general, for a while, but it all just seemed so confusing. the animations and visualizations in this video were amazing, and helped finally feel like i have a chance at understanding things! thank you so much for this amazing video!
Just paused at 8 minutes to say WOW! The animations! They really help to grasp the flow in a much easier way! Thank you!!! 🙏
As ever, very nice video, accompanying explanation, and pleasingly simple circuit.
One needs to distinguish, however, between compression and limiting. Limiters direct the circuit to address the dynamic peaks, while leaving material below the threshold intact. Compressors attempt to achieve an overall average signal level, by limiting peaks in the manner you've illustrated, but also *increasing* gain when content is well below the peak threshold. In practice, the two can sound identical with adjustment of controls, but there can still be audible differences between them when controls are set differently.
One of the phenomena compression can result in is often referred to as "breathing". Since analog compressors generally have no means to differentiate between pianissimo signals and background noise. they dramatically increase gain when the input signal is small. If the release/gain-recovery time is long enough, the gradual increase in gain during soft parts results in amplification of background hiss that sounds like someone inhaling - hence "breathing". The cure involves use of as pristine an input signal as one can provide, and as quick a gain-recovery as is plausible. Limiters typically do not encounter breathing.
While not strictly true all the time, limiters often involve feed-FORWARD control, while compressors tend to use feed-BACK control. That is, limiters use the input to control the final result, after the gain is applied, while compressors tend to use the amplified result to adjust how the gain is set. That aspect plays a big role in achieving an overall average level-setting in compressors.
Another limiter/compressor difference that may not be quite so apparent in the percussion example used in the video is the impact of instrument, or other, signal sources that either sustain or have long decay times. Although we may perceive such sustain or prolonged decay as smooth, it is actually filled with a great many little bumps, often referred to as "envelope ripple". When simple half-wave rectifiers are used to extract information about signal level, that ripple in the resulting control-voltage can produce small rapid fluctuations in output level (or filter-frequency, when used to control a filter) that can sound like "distortion" to the user; especially if used in conjunction with control elements that are able to respond to very quick changes (one of the reasons why photocells are often prized for some forms of sound processing). The solution is often to use better rectification, as well as averaging the detected signal level over a longer period; the goal being to make the control voltage resemble pure DC as much as possible.
Again, as elegant as the circuit shown here is - and it IS elegant - it is really predicated on processing short percussive sounds, and would need more to be able to process longer-sustaining sounds without problem.
Indeed, this isn't actually a VCA, it's a clipper / limiter. It's an interesting journey but opamp based voltage controlled gain is fairly straightforward. There would be a lot gained by doing some reading up front, rather than trial and error. The Art of Electronics by Horowitz and Hill might be a good place to start.
This isn't really true at all. There is no difference between compression and limiting. Limiting is just extreme compression with an infinity to one ratio and a very very fast attack. The only time a "normal compressor" adds gain to the quieter part of the signal that's not being reduced by the compressor is if you have a makeup gain knob and you're using it. Otherwise I can make a compressor with a wide range of controls be a limiter quite easily. My Urei LA 22 compressor for example.
And plenty of limiters do have makeup gain.
@@Wizardofgosz Oh they can certainly *be* tweaked and dialed in to sound the same, and yes there is makeup gain. But there is a difference between rackmount units, like your Urei LA 22, and floor pedal compressors, which operate like AGC controls on budget tape decks. In those circuits, there is not really any "make-up gain". They are aimed at a narrow range of output signal amplitude, both attenuating peak transients and automatically boosting signal level, when it falls below some threshold.
FWIW, I built a pedal for myself, using the SSM2166 chip from Analog Devices (great great chip by the way). It's a general purpose preamp dynamics-control device, and can function like a limiter OR compressor, if twiddled just right. For instance, if I set the ratio to "infinity", but leave the threshold high, it behaves like a peak limiter, such that everything below the threshold retains all dynamics. If I set the threshold very low, and crank the gain, it behaves like a compressor, with very little in the way of audible dynamics.
Brilliant Moritz, this is such a great circuit and beautifully explained as always. The animated visuals are a treat, thanks for all the effort with that - I know it wasn't easy. Looking forward to building this sometime. Happy New Year when it comes :)
let me know how it went once you do!
Many audio signals from synths BECOME asymmetrical when they pass through a cap coupled stage. Any pulse wave with a duty cycle less than or greater than 50% will do this. Send a 90% duty cycle pulse wave into the DC coupled input of your scope. It *should* be symmetrical about 0V. Then change to AC coupling. The narrow phase of the pulse have a larger excursion above or below zero than the wide phase. This is due to the time required to charge and discharge the coupling cap. Even some of the example waves in this video show this. Since this is so, if you want your compressor to work well it doesn't make sense to throw away the negative portion of the wave. The negative half could have a significantly larger excursion from zero than the positive half. It's EASY to full-wave rectify the input signal instead. One or two op amps. These kinds of circuits are called precision rectifiers and there are probable a dozen different types available on the internet. That way you get accurate compression of asymmetrical signals.All the famous compressors and limiters derive the side chain from a full wave rectified version of the input not a half wave rectified version. It's so easy to implement it makes no sense to throw away half the signal and wave your hands about audio signals being symmetrical about 0V. We're only talking about $1 worth of parts.
I finally understood what a VCA is. Thanks.
Hi Moritz, excellent job. Just a little add on. On every compressor one usually loses some level of the signal, therefore in the output stage you will need one more potentiometer to change the gain of the output stage to recover the original input level.
good call, will add!
@@MoritzKlein0 You could also add a mix control between the input signal ("dry") and the compressed output ("wet!") which gives you instant parallel compression. Should be a straightforward output mixer stage between the two signals.
If you're actually compressing then you have to be losing input signal. Compressors make things quieter. But yes a makeup gain knob will compensate for that.
@@Wizardofgosz Not necessarily. Compression usually means: compression of the dynamic range, not the volume/loudness. Therefore: if you'd like to just compress the dynamic range (in contrast to limiting the peaks), then you'll need a make up gain.
@@cls9474 You have no idea what you're talking about. Compressing dynamic range is compressing some of the gain or the volume. Compression only makes things quieter.
sounds pretty good. i think fully rectifying the cv signal would catch initial negative transients that you are missing and improve attack response. that's the only thing i would add
you mean rectifying the VCA's output before detecting the peak, right?
@@MoritzKlein0 I mean fully rectifying the audio input signal you are using to detect the peaks. if the input audio signal has an initial negative transient instead of + then your VCA signal will be delayed by that missing half wave
Thank you Moritz! Great explanation and I really like the animations you made.
I'm amazed that all this can be achieved with a handful of components. Not an Arduino in sight!
Great description of the functionality. Thanks for the video.
Absolutely beautiful! I love these types of breakdowns!
Your descriptions are, as always, clear and simple. And I love your animations.
So much dedication on this video. Thank you so much for making it, its so useful and wondrous!!
Thank you so much for this!! Ive been waiting for this type of video to start making my own comp. Time to get to work!!
I love your clear and visually decription - great.
Genuinely very detailed and well taught. Thank you for showing this. Love the content!
Awesome video! Always super informative and well-explained. Hope you keep making more great videos this year!
awesome video! love the animations, they make everything feel much more intuitive
Moritz you are great. Thank you for all of your hard work to spread this knowledge!
absolutely astonishing how well you put together this info.
Brilliant walk through and animations! I especially like the step by step explanation and problem solving when the next issue arise. Thanks! 😊✨
Beautifully explained, you're a great speaker.
Your use of animations is great - it really helps to understand what's going on in the circuit. Nice work!
Very thorough easy to understand explanation, great job
What a great explanation of compression circuits - these videos really helped me whilst studying Audio electronics
Nice explanation and walk-thru !
youre videos are extremely helpful and a major godsend
This is by far the best explanation I’ve seen on compressors and the building blocks involved. Thanks a bunch!
Animations were very helpful for the explanation! Thanks!
This was a great video! I especially appreciate how you went into your circuit design process, building it up on a breadboard and addressing any hurdles as you came across them. Great work!
so much knowledge, well taught, with meaningfull explainations and stunning visuals. I learnt a lot. Thank you for this amazing work!
Wow, your educational videos are superior to all others. So elegantly constructed and informative. I thank you.
Toller klarer Stil, tolle Videos, danke Mortiz!
This is so elaborate and well explained. Wow. The animations are great too. Thank you!
Dude, you are amazing!!!!! You explain and show things just how I like it straight to the point, concise explanation no bullshit.
Thank you so much!!!!!
Best explanation how basic compressor works I ever seen.
I've been binging your videos. If only electronics at school was explained how you present it! Thank you so much for your efforts, looking forward to more videos.
Great stuff in this video ... thanks a lot for your in depth analysis
Awesome video. I’ve been really interested in building a compression circuit so this is kind of a godsend. Really great video structure too. Thanks
circuit using diodes as variable resistors always make me happy and smile. they are always so surprising but work great. thanks!
Amazing, thank you for bringing this subject to life. Great graphics, animation and as usual clear and deep explanations.
Appreciate that you shared from the process of designing vs explaining a schematic! This definitely shed some light on a few basic ways compressors can have unique characteristics. Thank you for the hard work!
Explanations are very good with animations helping people visualise what is going on.
Those who are into pro audio side of compressors might like Gyraf Audio diy 4k compressor explanation as it shows pretty simple, typical VCA compressor, explaining how each part works and interacts with others in easy to understand details. Also shows typical balancing circuits, use of IC based parts like THAT VCA's, detectors, etc.
Ian Bell of Custom Tube Consoles had or has example of simple opto compressor, i'm not sure it is still there although whole diy part is more than worth checking, same for Gyraf's.
I will always be thankful to people like Moritz, Gyrad and Ian Bell, not many take their free time to explain this matters to beginners, or even more advanced pro audio electricians/designers. Many thanks, wish you all the best in 2023.
The animation is great ! Really helps
Great videos, as always !
Man ! I loved this ! Learned so much from your video :)
Thank you, Moritz, for this outstanding video! It was one of the best that I have seen in a long time! Very comprehensive and comprehensible!! Tempted to get your series of modules just to support you in this effort!!
starting the year with incredible stuff! thanks so much for all your effort and great content, you are a truly unique channel in youtube 🔥
Have been watching this channel from the beginning, these animations are so good at explaining these concepts - this channel is a such a good resource!
Best compressor walk-through on Earth!
Finally !!! I was hoping you would touch the subject!! Awesome content my friend. My best youtube suggestion video
in ages :)
The Grafiks are amazing. Well done
Your visualizations are wonderful and these videos help get my head around a lot of EE concepts xD
I always wanted a video which explains how compressors are engineered and never found one on YT, to this day. Thank you very much! Finally I got some insights.
Loving the diagrams. Gives a really good way to visualize whats going on. Its kind of what my mind see, when looking at a circuit diagram.
Been getting into DIY pedals lately, I must say you may be the most concisely informative 'tutor' I've stumbled across. Learned a ton, thanks.
I have been looking for a way to make a diy compressor. Thanks Moritz!
This is really great! I'm just diving into circuit design, so this was still over my head, but you explain things so well that I started to get it, even though I need to understand the real basics first. I'll definitely be checking out your other content! thanks!
Brooo cool! Excited to see this!
This is one of my best electronic related videos that I watched so far. It did give me some inspiration on how to multiply two signals together or how to do frequency modulation.Thanks.
Excellent presentation quality - you must put a lot of time and creative effort into each video. Thanks Moritz!
Thanks for the video! It's a lot simpler than it seems, which explains why this was doable back in the era of vacuum tubes(/valves). Love the animations as well. 👍
Amazing work ! Wanna see more of this in the future ! Keep going man
This just helped me so much in understanding compression, thank you!
The add level of quality was really noticeable with this one. This was a great video.
Figuring out how to make a sidechaininng compressor has been on my radar of projects i'd like to do and then stumbled across this awesome video! Thank you so much!
you are a real electrical engineer. you are the sabine hossenfelder of electronics. no gbledygook no bullshit. i have zero respect foe 99 percent of audio experts . but you you. ypu are the man.a
Another great video. Loving the Animations. 🔥 🔥 Luckily my DIY system needs a analog compressor. Happy new year 🎉
This why I like the most on the electronics field of knowledge. Amazing channel
Very nice work! Thanks a lot!
This video, explanation and animation is truly amazing! Please do one on EQ and/or a Mic Pre-amp!!
Animation o_O. It's amazing how well fluid pressure analogy works here. Oscillating membranes are mesmerizing.
Its the first time i really understand what a crompressor does! Thank you!
So glad I found your channel. Went to school for mechE, this is basically all magic.
I am really compressed by this explanation Moritz. 😜 Great video.
Holy crap i think I actually understand compression now! Seriously, I can't wait to know what I'm actually tweaking next time, big big thanks!
Wow it's very simple at the same it's very effective good work sir
This is an amazing resource!
you are the perfect teacher of delivering information thanks a lot.❤
Excellent job! Thanks for sharing!
I’m a current EE student with a budding passion for computer music and find this video incredibly inspiring. Thanks for the detailed explanation and impeccable animations!!
You sir, by the noticeable loudness difference and perfect clarity of your depth and clarity of your voice, definitely know about compression.
Diese Videos sind einfach so informativ wie eine Doppelstunde Physik Leistungskurs, wirklich sehr gute Qualität und man kann einfach alles so leicht verstehen!
Brilliant content. Very well done Indeed. Thank you 🙏
Moritz great one! I will add this one to my build list and it gives me some confidence to do it having built your VCA. The side chaining feature is cool in this - I don't know the term but I believe I have heard the effect. I've still got to finalize the breadboard version of your ADSR - still playing with and understanding a bit. Thanks for being a great teacher and resource for the DIY mod community!
Amazing video mate!