I know its been a while since you made these but, THANK YOU!! Thank you so much for sharing all these. Im getting so much more from these than anyother video thus far. And an actively gethering materials and odds n ends to follow along with the unit builds 😊😊😊
Hey. Found your channel searching for reverse avalanche. Im pretty sure I've seen you post in the synth diy fb group. Great series of videos. I will be watching them all. Cheers.
OK here's a couple of ideas for possible mods to the basic circuit; Disclaimer: I haven't actually tried these yet, but I will as soon as I have time to play with it... 1. Swap the positions of the potentiometer and the 1K resistor - that would allow a single pot to control the pitch of multiple oscillators (maybe include a small preset pot for individual fine tuning). This might need a diode between the main pot and the 1K resistor to avoid interaction between oscillators, though this might not really be a problem - I'll let you know when I get around to testing this idea. 2. The 12V-18V limitation might not necessarily be an issue in a modular synth with a dual-rail power supply as most of these will be +/- 12V, giving a potential 24V across the main power rails. Not sure if this may need a bigger resistor in the 1K position to limit the current, but if you're going to build this into a module, this might be a viable solution, allowing you to source almost any bipolar transistor. 3. Vactrol LDRs are not high current devices, so using one to modulate the supply voltage to a bank of these may cause it to overheat :( 4. If you don't really need 1V/octave (ie. exponential control), then a simple short keyboard (perhaps an organ-type bass pedalboard) with individual preset pots per key (13 in this case) might be a neat way of actually playing tunes on a small drone vco built from this basic core circuit, based on the concept in point #1 above. Sure the 1V/oct standard has been around for a long time but unless you're planning on using it with commercial sequencers and/or MIDI-CV boxes, then you really don't need it, and linear VCOs are much simpler in many respects (I built quite a few synths back in the 80s and most of those were linear)... Just a thought...
2 года назад
Some interesting ideas. :) I’ll love to know what you find out. The biggest downside of this design is that the transistor will degrade over time and fail. So it’s not a good design for a module. :/
Hi Cristian. If you take the led off the circuit you will get more 1,8 volts across the transistor, enough to bring even the 2n3904 into oscillation, and enough to have 1,75V peak to peak AC signal at the output with the BC337.
I've made 5 with the s9018 to work on my 9v skiff. I burnt a diode, because no resistor (the other work fine without one, just don't leave them all the way open and drop them on the floor), and I think the s9018 gave in on an other because messing with the circut too much. It very low volume, and it would'n even work with 22uf (or bigger) cap, so 10uf only. Haven't added a working CV, but think maybe it can become a cool drone or something on an amplified circut. Just used 100k pot's because I had some left, but it only works in a small range, so a 10k would be much better. Awesome video
I dont know... if I'm just living outside of reality and having auditory hallucinations or something but.. as far as my experience goes, if you dont kill the base pin.. nothing changes if you just connect everything else the same, and furthermore and ... rather importantly I would think... when j throw voltage at the base from say an arturia beatstep (I might have fiddled with some biasing) it simply controls the frequency of the oscillator right out the box...
Many thanks for what you are doing here - has peaked my interests and started me down the rabbit hole I'm afraid - thought I would share a discovery for another transistor to try that I had decent luck with to get stable oscillations at 12v (and below - down to 9V with the 4401! and that was with the LED in series still). Both do depend on the variable resistor and the capacitor value but everyone looking at this should be trying on their own anyway. I had some odd multi-packs of 2N3904's that included 2N2222's and 2N4401's - both of which where more stable (or would oscillate) below 12V than the 2N3904's!
5 лет назад
Thanks for the information and nice that you experiment. Sorry for luring you down the rabbit hole. 😂 Modulars are addictive. It is all I think about nowadays. What module to make next. 😉 Keep on experimenting and let me know all the cool stuff you figure out. 👍
Hm, it seems like i can't answer your message directly. I am powering circuit with +12v and gnd from DIY PSU (where is separate "+", gnd and "- " outputs awailable). I should measure output from 10k pot, its so obvious) Thanks for reply!
Wow! I'm making a very similar journey to you. I've been inspired by LMNC very much, so have built a case, 50x50 cm out of an old drawer, built a dual power supply from a kit and just made 3 reverse avalance oscillators. So far, it just drones! I too found the transistors that LMNC used were hard to get here in Australia, so I got BC337s as well. They do indeed oscillate higher and better than the 2N3904s that I first tried. I also tried different color LED's but the blue and green ones seemed quieter and didnt seem to sound so nice. LMNC is using just red ones so maybe he found the same. At the moment I'm trying to get the oscillator to stop at the pot's highest resistance (counter clockwise position), the 10k pot doesn't do this. Do yours? I haven't compared my output levels yet, but if it's low I may yet build the output buffer like yours. I can't wait to add CV, I have LED's and LDR's on order. I am going to build a Baby8 sequencer with hold stop and reset buttons on arcade switches. I have breadboarded an audio to trigger circuit which steps a prototyped sequencer from my computer so with my audio interface I can send a click to sync it up to my DAW. It's so exciting! I'm looking forward to watching the rest of your work. It's now some months since you published this, so hope it went ok. Peace, Punk Duck
5 лет назад
That sounds like a good start. As for my oscillators I don’t use reverse avalanche vcos anymore. I switched to one design around a 4046 and one classic two ops no saw and square wave vco which also tracks cv better. I’m also going to build a sequencer ASAP. To make my rig more musical. :) I really like the audio to sync idea. Do you have any schematics or similar you could share? Anyways thanks for sharing your journey so far. As soon as you have a video showing it of let me know. :)
Hey Kristien! Love this series, which oscillator circuit do you think is better for good CV (1volt per octave) for keyboards etc?...., I've made a basic 555 oscillator but CV is all over the place!!
3 года назад
The only 1v/oct I built is the aacvco it has NOT good tracking. But works for two-three octaves. There are many oscillators out there with much better tracking. Check out some cem3340 designs or if you want to make the reverse avalanche vco check out kassutronics design which has quite good tracking. Rene Schmitz has some simple designs with cv tracking aswell on Schmitzbitz.de
3 года назад
It is also very important to tune the exponential converter. It is a tedious process that needs to be done.
the only 555 based vco's Ive used that track well at all has been the wasp and Thomas Henry's 555 VCO which is surprisingly great.I want to mod my atari punk console for 1v per 8ve tracking.a pretty good VCO for tracking is the Moritz Klein Shapes VCO ( pulls heavilly from Rene's work) but, tracks really well once you get it calibrated
Wouldn't it be a good idea to add a 220 ohm resistor between the cathode of each led (including the Vactrol) and the ground? And... Why using a DUAL op-amp, if you are using a single section? I guess a TL071 would fit perfectly.
5 лет назад
Yes. I think I use 330ohm. It depends on which diode you use didn’t I show that? In the ones I have I have resistors. And yes a tl071 would have been much better. Didn’t have one at hand was the reason for that.
Hi Kristian, i'm a big fan and just started this journey too. I have some soldering and electronics skills but building analog synths is something different. I have build 4 oscillator modules (reverse avalanche) with BC517 transistors. I found out that this transistor has more output, but also lower in pitch (even with smaller capacitors), now I'm figuring out how to amplify them all. probably using a TL074 op-amp, but how to approach this best? for each oscillator one op-amp? or hook all outputs together and then via op-amp? this I cannot find on the internet. Your help would be greatly appreciated. Also i have questions about the vactrol too. Thanks in advance for your reply :)
3 года назад
Congrats on jumping into the synthdiy rabbit hole. ;) if you continue watching episodes in the miaw series you will find a simple mixer and a buffered mixer. These two are good for mixing the signals of the oscillators you built.
@ Hi Kristian. thanks for your quick reply. I'm a musician and play keyboards and fiddling with drum machines from the early 90's. Never occurred to me to build a synth myself. I currently own a Yamaha DX7 and I know how to program, and recently I have bought a Roland Juno 106. So VCO's VCA's LFO's etc etc does ring some bells :). Just figured out that the BC517 transistor has a lot of output, so no op-amp needed. the overall sound is also way lower, even when using a 1uF capacitor. I have fun experimenting with this. next step is the Vactrol. have a nice day. gr Maarten
Hi Kristian, hope you doing well. May I ask one question regarding the Vactrol? the CV amount you have, is that only a 10k potentiometer in series with one of the vactrol's leg? So that you can control the amount of light falling onto the LDR? or do you have a potentiometer on the CV input jack? no idea if that works different. thanks in advance for your answer.
So I built this, and it works, but it is extremely quiet until I touch the positive (an open lug on a pot). While this is cool and an added bonus - I really don't know why it is happening. I currently have it working and my output jack isn't even grounded! How is this possible?
5 лет назад
The ground in a modular is "strange" and sometimes not used at all, look at all modules using banana plugs, which is just the signal, no ground. As for the colume, I have heard many people having trouble with the Rev Ava Oscillator, it seems that it is very dependant of the transistor, and will wear out over time aswell. All I can say is double check your connections, and maybe replace the transistor? You could also add that open lug to ground as you touching it basically is that.
@ So strange... when I add the open lug to ground it shorts out. Thanks for the heads up on the potential to wear out though... good to know in advance!
Hello! I am currently testing a simple avalanche OSC (without CV input or buffer). The first BJT i was testing is 2n3904, but it needs higer voltage to start oscillate than BC337. I've bought a bunch of BC337, and it seems to be another problem now - the oscillation starts only on a half-way of 10k potentiometer :) I was looking sharply to your demonstration, and it seems like you don't have such problem. What can it be? The range was just fine with 2n3904.. I've been trying different resistors before pot, different value of pots (5k behave just as 10k, only 2-nd half, and 1k is going all the way, but with awfully narrow frequency range. Larger pots is useless). Did you face that kind of problem? Schematics are all the same, i am confused. Also i noticed that in Kassutronics schematic circuit is powered by 12v, but he uses 2n3904 (in my first test they was only start oscillating at 16-18 volts). Maybe i need to breadboard his schematic to be shure. And yes - thank you for this amazing series! This inspires me to continue working on my modular)
5 лет назад
How is it powered? I have the halfway potentiometer problem when driving a 12v-Gnd osc with a +12-12v cv pot. The freq range wasn’t that good for me either and even with amplification it is still very quite.
I have read that it often takes a few tries/a few NPN's to work. If it does not work does it ruin your NPN or is it still good to use it for something else?
4 года назад
If it doesnt work, it just means the npn hasnt the right qualifications. And they should be good to go in other projects... If they start to smoke and/or smell bad, well then its a different situation ;)
Hey there, with this module your sheet is messed up :( First you say - it is only one Jack, when it is obviously two of them, right? Second, in cell number M73 you say we need two parts, but two parts of what? It is a row right under the 470uF 35V Electrolytic Capacitor Could you please clarify it? But of course, thank you so much for your videos.
5 лет назад
Thank you for the heads up, and sorry for the inconvenience. I fixed the sheet so it should be correct now (I hope). I added a few more notes to the cells where you can choose components. The two parts on the empty row is gone... As for the jacks, I explain in the video that for the CV input you need to make a Vactrol circuit (shown in the next episode after this 2.1). And in that module if using it as a CV-input to the RevAvaVco then you get another input from that... So watch the next episode aswell for the full explanation of this module with CV... Oh, and make sure you open the latest version of the excelsheet as I just fixed it...
Very cool! I breadboarded Look Mum No Computer's idea and I'm testing lots of different transistors. I'm using 12V and having no luck with pile of 2n3904s. Obviously 12V is too low. However bc547 and bc337 work very well. There's one minor problem. No output where output should be. But I'm taking it from LED legs instead. Actually I removed the LED and just put the output there. And it sounds great. But why there is no output on 100k? Am I missing something? Anyway You got new subscriber! Cheers :)
5 лет назад
Sorry for late reply. I know there was some quirk on the lmnc schematics that I changed but can’t remember now. I use the bc337 and that works. The 100k does dampen the signal a bit maybe that is it? Remove the 100k and then directly into the opamp buffer if you use that? I think I will try that too. To get louder sound hopefully (it is a bit too soft in comparison to the other vcos)
@ Thanks for the reply! No worries for being late. In the meantime however I have found where I was dumb and maybe too tired to think :). In the begining I was using just a small speaker to test it and that's why the regular output with 100k didn't work thus I took the output from led legs. And when I went to my guitar amp it didn't work with this alternative output either. Then it's hit me. Amp has high impedance input so of course it didn't work with this. I redo the proper output with 100k and it works like a charm! Added 3 more oscs with different caps and a little drone machine has been born :) It was 100% my fault. My amp was too far from my workbench so of course it was prone to mistakes when you're running up and down the stairs with the breadboard :D
5 лет назад
nusior lol. Great you got it to work! A video showing it off and some sounds maybe? ;)
@ Yeah, definitely! It just needs some tweaks and temporary enclosure. And for some reason none of the 5mm LEDs that I have work in this circuit but 10mm LEDs work fine :D And since I had only two of them i just put 1n4148 or something in the other oscs just to finish something that day :)
Hi there, I uploaded a short demo here: instagram.com/p/BsYXLmfnACQ/ It's cool but it gets boring quickly so I HAVE to make next things :D oh btw I found out why those 5mm leds didn't work. All of them in that batch are just reversed :D Cheers!
With ending the VCO's, did you ever find a decent (easy/cheap) sine wave source to build? I would like to add a sin wave if possible. Thanks
5 лет назад
No. Not yet. I found a squ to saw shaper which I’ll try in a bit, but sin seems harder. Have tried a few circuits which didn’t work. But will continue searching. :)
@ I'll be watching out for them! Interesting that the most fundamental of waves is the hardest to produce. Before finding your series I was doing some searching to build one and most were a part of bigger systems. I'm sure you have seen these, but the ones I found were: Ian Fritz, The Teazer; Catgirl (CGS) 48 VCO; Thomas Henry's VCO1, and; Yusynth VCO. Like the AAC module, I wonder if the various waves can be pulled out separately. Thanks!
@ Use this maybe : www.multisim.com/content/v5kkSUdCsvbbX9TKSLkSSE/6-diode-3-segment-triangular-to-sine-wave-shaper/ I found it a couple days ago and in circuit sims it gives a sort of squarish sine wave with triangle input, but the circuit is really simple. With a switch or two disconnecting the top or bottom diodes at will you can vary the waveform in other interesting ways as well. I am going to breadboard it and try it with the reverse avalanche thingy that I built last night. I had issues with LMNC:s reverse avalanche as well, but with a small, low current LED it works fine on 12 volts and sounds like this : ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Kl-DDVbyQqA.html
Caution! At about 11:00 you mentioned using half of a tl072 op amp. Leaving the other half uncommitted can lead to unusual circuit behavior or undesired functionality... see this article about properly handling the floating op amp section. I’m not a hater, I love what you’re doing, and you’re showing everyone that they can do this, but we both know that as in all things, we all face fails and many of us will likely not succeed. You are very optimistic yet you are honest in your lectures, I feel your pains too. Maybe elsewhere you mentioned this about op amps, I’m not trying to point out any mistake, someone out there may not know about this... www.maximintegrated.com/en/app-notes/index.mvp/id/1957 Thanks for your contributions and sharing!
5 лет назад
Thanks for the heads up. I’ll try to cover this in my epilogue episode. There are a lot of mistakes I made doing this. But that is the way to learn. Thanks for teaching me this. :)
somehow the ones i built only play for half the knob range, past the half they shut off, same with CV, they only play for like 2 or 3 volts
10 месяцев назад
You can try other transistors. As it is very sensitive to their performance. Check the link in the description for which you can try. This is a very controversial vco design. If you want better everything you should try another design. The 4046 is a simple one. 40106 even simpler but not cv-able. Or the AAC vco which is the best one I did in the beginning of this series. It is actually timetable to 1v/Oct. hope it helps a bit.
@ it's way too simple for proper tracking but it has a lovely sound and I like it specially because it was my first vco, I built it in a dual packet with an option for mixed outputs or 2 single ones, but what I found is that due to tolerances it behaves different no matter what :) I will probably change for a higher voltage transistor and see how it goes; also if you change the led for a multicolor led of the kind that changes "randomly" it produces a cuasi-random change in the pitch I did the 4046 as well, but since it has an inverted input the keyboard plays backwards and I've been lazy about adding an inverter for the input, also I got some AS3340 but haven't built the module yet Thank you for answering!
