Moritz Klein - 2024-10-16
Build your own Delay as a DIY eurorack kit: https://www.ericasynths.lv/shop/diy-kits-1/edu-diy-bbd/ LABOR in the Erica Synths Webshop: https://www.ericasynths.lv/shop/diy-kits-1/edu-diy-labor/ Support the channel... ... through Patreon: https://www.patreon.com/moritzklein ... by buying my other DIY kits: https://www.ericasynths.lv/shop/diy-kits-1/ Simulation in CircuitJS (discrete component BBD): https://tinyurl.com/2dbdonlb Join my Discord community: https://discord.gg/KCwpyAsFpb Here’s an interesting problem: how do you create a delayed duplicate of a sound without recording it to some sort of storage medium? Back in the days before digital signal processing and cheap, abundant memory, this was a prime engineering issue. Until two Engineers named Sangster and Teer came up with a deceptively simple solution: the bucket brigade delay. In this video, I attempt to reverse engineer the architecture of a classic BBD, recreate a bare bones version on the breadboard – and then use a proper BBD chip to design a simple DIY audio delay. If you want to build along, here's the bill of materials: BILL OF MATERIALS RESISTORS 2M2 x1 100k x8 82k x1 56k x1 51k x1 47k x1 39k x1 22k x3 10k x2 6k2 x1 4k7 x1 CAPACITORS 1 uF x2 10 nF x1 1 nF x1 (more if you want to build the discrete component BBD!) 220 pF x2 TRANSISTORS & DIODES 1N4148 (small signal diode) x5 J113 (N-CH JFET) x1 (more if you want to build the discrete component BBD!) POTENTIOMETERS 100k (A104) x1 100k (B104) x3 10k (B103) x1 CHIPS TL072 (dual op amp) x3 V3205SD/MN3205 (BBD 4096) x1 4046BE (PLL) x1 SWITCHES SPDT (Single pole, double throw) x1 Chapters 00:00 BBD Overview 01:43 Analog Sampling 10:09 Sample Transfer 16:28 Buffering & Listening 19:50 Dual Tap Reconstruction 23:01 More Stages with the V3205 27:55 Reconstruction Sampling 33:26 Dry/Wet Mixing 34:41 Feedback 36:04 Flanger Mode 41:43 Inhibit CV 42:59 Sound Demo & Outro
This is a higher quality explanation and demonstration than you would likely find in a university. Really nice work.
What I love about the BBD is that it blurs the line between digital and analog; Two things that most people consider to be sort of mutually exclusive. You get a quantization of time, but the amplitude is fully analog.
agreed – plus i love how simple it is, especially compared to something like a PT2399. BBDs really feel like a super precise solution to one specific problem!
Yeah. First it is analog, then discretized, and lastly digitized. This chip/circuit just omits the last step.
Lost me at dry/wet mixer 😮
Wait this isn't a fully analog circuit? Why?
@@robertosutrisno8604 it depends on what you understand by analog & digital. since a BBD is splitting the signal into samples, you can make the point that it is digital on the x-axis (time) – since the signal is divided into discrete blocks. the y-axis (amplitude) is still analog, though.
Not only from the technical perspective, also the filming, illumination, motion graphics, narration quality, used didactic tools... absolutely beautiful. This video is a piece of art
Superb video - this is quality content that makes YouTube worthwhile. I've no desire to build my own BBD based delay, but learning how they work is fascinating.
@@chriswareham glad to hear :)
dammit I'm the other side of nerd, now there's a youtube video let's 'ave it, try and build one as well!! :P
@@MouldySoul that’s the spirit!
Probably the best explanation of how a BBD works.
Incredible video, can't believe information like this is available for free.
From engineer to engineer, thank you!!!!
I feel like this video should count for credit towards an electrical engineering course... great work!!
Not enough linear algebra
Yess
Man I wish I had this video when I studied opamps 30 years ago. All that abstract theory makes so much sense with a practical example like this.
Thank you so much for this fantastic video. I'm new to electronics, but this has really helped me understand how bbd works. Your insight and ability to communicate a complex subject clearly is exceptional. I'm going to have a go at building this on a breadboard.
Thank you 👍
This is an AMAZING teaching video. I have basic electronic knowledge and understood everything. Even if you’re not looking at building a delay/echo system, there’s many basic electronics lessons contained in this video so it’s a good teaching lesson.
SO many instructional videos will just say "We won't do x because it causes problems." and move on. The way this video makes the problems happen and demonstrates why they're an issue before fixing them makes it such a great educational resource.
glad to hear, that’s exactly what i’m hoping for :)
Really interesting as an audio programmer to see this weird transitional tech between analog and digital. Top video.
This is too good to be free on the internet. Outstanding.
Awesome sound demos at the end too. 👏👏
hey thanks, glad you enjoyed it ✨
I really appreciate the level of detail in your videos. I studied as an ME but my work involves a lot of EE knowledge that I've been learning on the job over the last couple of years.
The graphics in your schematics, specifing what chips you are using and why, and just explaining you're overall design process actually helps me be better in my job.
Looking foward to more videos, truly
oh wow, that's great to hear. 🙏
Excellent explanation of BBD operation, intricacies and 'pathologies'! Thank you for the fine detail description. Also, great use of PLL 4046 using all the internal functions, while NOT making a PLL from it!
What is crazy is the BBD is old technology now. But the analog nature allows for some charming quirks and actually great analog interfaces compared to microprocessor based solutions. Being that sound lives in the analog realm and the lack of code is great. An amazing build thank you
true, but as far as i know the idea lives on in CCD camera sensors 📷
...which have been almost completely replaced by CMOS image sensors today.
Love this! Great explanation of how everything works, why everything works and in a lot of cases why something DOESN'T work.
Great video! Thanks for making it! I’ve built a couple PT2399 delays, but that chip contains much of the external components needed here. I had wondered why BBD delays were so much more complicated. For anyone interested,look up the data sheet for the PT2399, it shows a very basic delay that really just needs a voltage regulator,a couple caps, couple resistors, and a couple pots. It’s a fun and easy circuit to play with.
the pt2399 is extremely complex compared to a BBD chip - that’s why the driving circuit can be so much simpler :)
the PT2399 is notably not a BBD but in a way it's sort of the logical next step. turn the signal into a binary stream using delta-sigma and then you can use a really long shift register and cut down on how accurate/big the capacitors and transistors of each "stage" need to be on the die.
@@famitory yeah, I'm quite aware of that, but it's the only real frame of reference I have to compare it to. And while it is digital, it was designed to emulate the sound of the old bucket brigade type sounds. A lot of the control options are pretty similar too, such as being able to drive the clock speed with a modulated source, the raising and lowering of pitch as the speed is adjusted up and down, and the gradual darkening of the signal. It also does some wonky distorted sounds when you try to make the delay length more than it's designed for, similar to what he did in the video.
@@MoritzKlein0 exactly! That's why I had looked at BBD circuits in the past and had no idea what was going on 😁
As a gear nerd who realised in the mid 80’s that not all BBD delay pedals were created equal, this video is fascinating.
sad4096 ?
Sampling the signal again at the BBD's output is genius! I also love the creative front panel design. Amazing video and amazing kit as always :)
@@taidi4038 glad to hear you like the front panel design - thought it’s time the modules get some visual spice :)
Really love these videos, can't wait to get my Labor here soon and start messing around with some of these edu-diy circuits
Just found your channel. Top notch teaching. I am now a subscriber.
I learned so damn much in this video, was just getting the hang of the basics of circuitry and this put so much of the basic knowledge into place. Combined with the real examples and argumented decisions at each stage had me hooked. Thank you for this!
Such elegant explanation of a very elegant solution
Wow. I’m just getting started in learning electronics as it’s something that I’ve been interested in knowing how things work for a while and whilst I found it a bit difficult to follow along with at some points I understood the majority because you delivered the content very well. An outstanding video thank you for creating it. Now I’m going to check out your filter videos 😊
YES! I've been asking for a BBD video several times, and right as I wanted to try my own hand at it, a wonderful Moritz Klein video appears to help clearly explain everything about it! Thank you for these videos (and this one in particular)!
perfect timing - hope the video will help!
As expected, another superb video from Moritz. I got just as much out of your knowledge of the PLL as I did from the BBD circuit approach. Fantastic. Thanks Moritz.
that PLL chip is seriously feature packed :)
What a lot of memories with BBD chips. Nice video.
Your channel hits the perfect sweet spot of "technicality"! (At least for me - I studied EE/CS, but since college, I had zero experience with circuits and forgot all the annoying transistor calculations)
Still engaging, skipping on some of the unnecessary details and calculations, but not "dumbed down" and just perfectly enough to appreciate the beauty and smartness of those designs, explaining exactly what was challenging and how it was solved. :)
And while this might not be enough to build such a circuit entirely from scratch without your designs, it's again perfectly enough of a starting point if someone wants to dig deeper.
that’s exactly the balance i’m trying to hit - glad to hear it works for you!
Exactly, I teach analog electronics and digital signal processing at university and I'm always dumbstruck by Moritz didactic quality. I do recommend his videos to students and colleagues!
I totally agree. I haven't touched analog circuits since college as well, but found this super fascinating.
Great presentation! Got me reminiscing of playing around with the Reticon SAD1024 BBD chip back in the '70s for phaser/ flanger effects for guitar and vocals.
You Sir, have become a professional video creator in terms of content and quality. Kudos.
how is this video so effortlessly cool and well thought out
Best BBD explanation I ever seen! Thank you!
One the best channels on YT.
Awesome video! Perfect amount of in-depth explanation yet keeping things easy to understand and consume. Great job.
These videos are masterpieces not only of engineering but visualization and narration / explanation / education. Thank you. I bought a couple of bucket brigade chips to experiment with building a chorus effect pedal and was puzzled why the chip data sheet recommended use of a specific related timing IC. This explained why a dual clock source is required.
i think low output impedance on the clock generators is also important (cause the mosfet gates do pull in current when switching on). so that’s also why they made those special companion chips.
This is just amazing. The video came out super clear and ultra interesting. By FAR the best one you've uploaded, keep doing this please! Thank you!!!
@@lucanotreally314 really glad to hear :)
I’ve always wanted to design a BBD with a variable output filter tied appropriately to the clock frequency. This is a great point to jump off from and an amazing general learning resource as always. Thank you for your continued work on increasingly complex projects!
good luck with that project, sounds like a fun one!
I had thought about this with some variable sampling rate DACs too. It's on my "someday" list to experiment with adaptive filtering on the Sega Genesis PCM channel to settle the "muffled vs. scratchy" trade-off of different audio circuits used over the console's lifetime.
Reconstruction sampling instead of the traditional hardcore rolloff makes a huge difference in preserving the fidelity, and avoiding clock noise at very low frequencies. This means getting longer delays with smaller BBDs. Night and day... I'll definitely test this approach.
Thanks for the amazing explanation and presentation.
Your videos are such a huge inspo for me as a synth DIY geek. Amazing as always!
I feel obliged to start this journey. Ive found the teacher that talks as an engineer not just plastikman
Pitch...swing ... CRACK and OUT OF THE PARK!!! Another brilliant video and teaching session!!! Well done.
thank you :)
The re-sampling is so smart!
We should thank Norway for making the invention of this circuit possible!
These BBDs were a huge breakthrough. I have a book that tells you how to make most effects with BBDs, not just delay. Flanger, chorus, etc.
what the name of the book ?
@@darmstard Wouldn't help you. It's long out of print and not in English.
@@CristiNeagu thank you anyway
just out of curiosity , whats the name of the book ?😅
@@CristiNeagu ok. what's the name of the book tho?
I have used many BBD chips in circuits along with synths, distortion, fx, for years, and I had a basic understanding of it but it's so cool to see one built from the ground up! Thank you for this great tutorial!
i was really happy when i managed to make it work using JFETs - so useful to be able to check the signal at every capacitor in the chain!
Amazing video, well explained and recorded. From the first half part, I learned a lot.
Just three notes:
1. You completely missed to mention the Aliasing issue, that happens when clock freq. goes below half the maximum frequency of the input signal (Nyquist-Shannon theorem) --> an input LP filter is really needed, tuned wrt the minimum clock frequency. Lot of the sounds of the video come from that fenomenon.
In other words, the bandwidth of the BBD circuit is always less than half of the clock frequency, otherwise you will get a lot of 'noise' in the audio band.
2. The two complementary clock signals need a small dead time between their edges (that is, there is always a short time when they are both not active); this is due to non instantaneous switching of the MOSFETs and will reduce a lot the spiking.
3. The flanger effect usually refers to delays that are a lot shorter (in the order of 1ms to 5ms) and the related audio effect is different from what is shown in the video.
Apart from these notes, I really enjoed the video and I thank you for such quality contents!
The obvious thing to do is to use more BBD chips for longer delay at higher clock rates. The clock rate should be more than double the max signal frequency. Then add proper higher order filters to get rid of all unwanted noise. So adding more BBD devices will increase delay at higher sample rates without distortion. Also one can tap signal between BBD chips for more interesting echo/delay effects.
CCD chips used in digital cameras work the same as BBD devices, but initial charge stored in each capacitor in line is determined by light level - it discharges them (IIRC). So process of getting the image data from the chip starts by clocking it out across the sensor to the ADC at the end of the line. In case of CCD chips propagation delay is a bad thing, causing horizontal tearing when recording fast movement.
Ah, then instead of modulating the clock rate, you can just manufacture more BBDs … no, wait, that's software thinking.
yes – but unfortunately BBD chips are really expensive. so this is not really feasible for a commercial product.
@@MoritzKlein0
Well, I found lot of ten for less than ten bucks, from China. These are clones, might not have the top notch specs, but are good enough for this usage...
@@MoritzKlein0it WAS done in various studio and broadcast kit though. Things got "very expensive, very quickly" in analogue designs
What a brilliant video! If I recall, there is another way that uses a shift register to generate a pulse that travels one by one from the output stage to the front in a rolling fashion. At each stage, the next stage is first emptied and then the gate is opened from the previous stage to fill the capacitor. This continues down the chain and then repeats. The output is a simple high impedance buffer and RC smoothing filter. Doing it this way removes a lot of the clock coupling. Anyway, absolutely brilliant stuff man, takes me back to my youth!! 🎉❤
Back in the late 70s and early 80s Radio Shack sold a BBD chip for projects. I built the standard one: voice actuated cassette recorder. When audio turned the cassette recorder on, the BBD gave the audio enough delay for the recorder to start recording so the beginning wasn't cut off. But the audio quality of the BBD was barely audio cassette quality. I recall it more like AM radio quality and I assumed that was the cost of using a bunch of capacitors to store audio. I was surprised to hear later on that BBD circuits could actually produce high quality audio.
that's a really interesting use case. maybe they applied really heavy filtering to combat the sampling artifacts and clock noise?
@MrSlipstreem - 2024-10-16
I used to use high quality BBDs (clocked as fast as they'd go to keep the quality up) as part of an analogue signal processor. This allowed me to monitor and process a signal in real time a few milliseconds before it got to the listener. Using an analogue discriminator and comparator, it was possible to recognise a scratch on a vinyl record just before it got to the output and replace it with something else less offensive to the human ear. Another comparator tracked the average background noise level from the vinyl, so the system became fully automatic with no need for any twiddly knobs to adjust anything.
This was back in the late 80s, and I can still remember to this day the satisfaction of designing it all from scratch (pardon the pun). It took a few weeks to iron the bugs out, but the finished project still works very well to this day.
@Galova - 2024-10-17
Some BBD IC? Just curious
@MoritzKlein0 - 2024-10-17
@@MrSlipstreem sounds like a really fun problem to solve. what did you replace the unwanted sounds with?
@jameslynch8738 - 2024-10-17
@@MoritzKlein0He probably used anything other than the tone in the video at #19:20 😉
@MoritzKlein0 - 2024-10-19
@@jameslynch8738 🥲
@gorloxian - 2024-10-21
Dude you old analog guys, I am in awe of. My "artist" name is a term from an exotic quad decoder.