Thank you for being foundational to start and working up from there. I also appreciate your slow and deliberate delivery of the information. Many synth guys get too excited and wiz through everything and I’m left scratching my head!

Tim, again a wonderful video. There is a way to get around the broken waveforms in sub-mode on the 921. Don't use sub-mode. Use range 32' and select scale OCT and turn frequency fully counterclockwise. So far so good. Now take the -6V from CP35 and pluck into the CP-3A-O EXT INPUT. If you turn the attenuator fully clockwise, you can go as slow as 0.02 Hz. One cycle takes 45 sec. Now take the second -6V from CP35 and pluck it into INPUT 1 of the CP3A-O. Turn the attenuator to position 5. That leads to approx. -7.5V. The cycle length of the 921 increases to 3 minutes and 30 seconds. That is round about 0.005 Hz. I think that's a pretty low LFO. The regular output is just 2V peak to peak. But, the aux out is -5V to 5V output. The specs say it only takes -6V to +6V input level, but, it seams it can take a bit more without wrecking the device (DISCLAIMER: No guaranty whatsoever). Same exercise with 921A and 921B. 921A fully counterclockwise, select Octave. On 921B select Range LO and frequency fully counterclockwise. One cycle is 20 minutes equals 1200s. That is 0.00083 Hz. Output is only -4dBu = 1.4 V p-p.

Thank you so much for this bright explanation of the differences between 921 and 921a and b. Loved the news flash. Take care, stay healthy, Dr. vanBakel

Thank you so much for these videos! These have been the best tutorials on the System 55 that I have been able to find by far.

Tim - LOVE these videos. As someone who is somewhat of a n00b and a new owner of a System 55, I find these hands-on videos super helpful!

Thank you for putting the time in on this video. Very helpful. I’ve been struggling to decide between the 921, and 921a/b and now I see reason for having a few of each.

Just discovered your videos, and really appreciate your thoroughness, pacing and clarity. Thanks!

Very new to the Behringer ecosystem (I bought a system 15 and then expanded it). I found this video fabulously informative - i'd basically ignored my 921A/B's as i could not fully understand them. Thank you for taking the time to explain it all in a clear and simple manner.

What did I witness! 👊☀️This extends the experience of emotions in the evening with what you’ve captured..

Another great video. Love the clear explanation with examples! Feel like I'm getting a solid education before I can actually afford a System 55 setup...

Thank you so much Tim, another brilliant video on the System 55 modules that I have had trouble getting to grips with. Easy to follow and very well explained all the way through. I love the System 55 and Behringer have made it possible for me to own the dream modular Synth but, in true Behringer style, the lack of information and instructions is confusing to say the least. I hope you will continue shinning the light on these modules. Great stuff.

So helpful and beautifully produced. Thanks for this.

Excellent video Tim, thanks. I'm currently building a Behringer System 55 and this vid has been really useful - cheers!

Superb channel i really appreciate all the time and effort you put into making these in depth videos

Thanks' for posting,Tim!Very informative! I knew there was a 'glitch' in the 'triangle-wave',but didn't realize that it affected the 'triangle/sine-wave' at different frequencies' !

Love the System 55 Vids Tim. Thanks again! As a 921 user, the clamping point low frequency newsflash fix was really helpful! To System 55 Users: If you have a spare 902 VCA you can use it to send -6V thereby using less space than the attenuator module

I'm not into modular (yet ;) ), but these sort of video's give me also more insight in synthesis in general. Besides that, your video's are always very thorough and of the highest quality. (It shows you're a photographer / videographer). Plus you have an excellent voice combined with your English accent, which always makes it a joy to listen to.

Once more a great, analytical video. Thanks!

Very nice! Just the information I was looking for......I couldn't figure out WHY they were both the same price and the 921 seems to have more versatility than the 921B..........Thank you.......By the looks of things, there may be advantages having both types in the system..........Very thoughtful video...

Yaaaaaaaay!!! Been patiently waiting for more System 55 vids :) (I will continue to patiently wait for more 2500 vids once Behringer ships the sequencer and mixer :D) *edit* I just now saw the sequencer in the background at the end of your video haha.

it was not exhausting at all, or pedestrian. great newsflash at the end for fixing broken waveforms. Thank you so much , i learned all the things i needed for the osc. :-)

Hello, my name is Peter, I just own the system 35, and very happy with, I just like to tell you that I learned a lot of y're explanations of the oscillaters. I hope in the future you will do also for the other moduals as well. Thank you for this giant helpful video.

Great and informative job as always! Thank you!

Thank you very much for this video, it has been very useful and informative, I have learned loads from it and really appreciate the time and effort you have put into it Tim . Fixing the the 921 sub was a great piece of brain work, well done 👍 , really looking forward to more helpful videos coming in the future, maybe you could add the Molevolent into the setup and see what comes from that

Hey Tim - I have a few of the 55 modules but no intention of buying any more but I just ❤ your videos 😁

I hard wired my 921a/921b vcos/drivers behind the panel, (Ive got four 921a's with three 921b's each, and have several 921's, Im glad I did this because it was always a mess of cables. Im considering further modding them with a clone/reproduction of the CV/Trig bus from the original system 55, and doing the same with the system 100m

I now have a Behringer System 55 - this extremely useful!!!

Very informative and very interesting. Many thanks

Worth noting that if you want to put a System 55 oscillator into a mixed Eurorack system, you'll want the 921. The basic waveform outputs on the 921 & 921B are much lower signal levels than typical Eurorack levels, but on the 921 the aux output has enough gain to give you a signal level comparable to other Eurorack oscillators.

Cheers Tim, very useful video

From all the time I spent on the Model 15 app from Moog, I came to a conclusion. I really like the 921A and B. The normal 921 is what I use to change the LFO rate on the modwheel. It’s pretty handy to have that. I love the 55/Model 15!

Thank you very much for your great Videos ! I read that in the 921A/B combination the linear/exponential converter was build into the 921A and the 921B had linear response. It tracks Volts/Hertz not Volts/Octave

Hi Tim. I have the 921 and have not noticed any issues with the sine and triangle waves in sub mode. However I usually just use the aux output rather than the individual outputs. But I’ve used the sine and triangle LFOs plenty of times and they always sounded smooth, and also sound normal at audio levels.

I own the VM900 series by Cherry Audio and learned some useful things from this video. Nice one man.

Excellent explanation, thank you!

Thanks, great video, really easy to follow,,

Good to see you haven’t gone down the modular rabbit hole.

very nice and detailed video < 3

Someone you could speak to regarding this and other synthy stuff is Marcus Fuller. He's an engineer and does Synth teardown videos etc. on YT. He has a moog modular and would probably be one of the best people to ask abou this. Thanks for this video. Very informative and I like this format Cheers!

I have 2 x 921 and the first one had the very obvious discontinuity you describe at lower frequencies and the other didn't. But I did manage to tweak the waveform of the first with the aid of a scope to be acceptable (indeed not perfect as you say) at both ends of the range.

Great! The fix of the waveforms in LFO mode is a big help. However, I tend to think that these VCOs were designed to be used exactly that way. Can't be an accident that the circuitry already contains the solution for this problem. It COULD have been documented in any form to help us modular rookies, but maybe it was meant to be Tim to show us a trick once in a while. It's more fun that way.

Who's a clever boy then? Thank you very, very much Tim.

The 921 is a really interesting design!

Nicely done

21:30 me suddenly realizing that US cop cars in the 70’s and 80’s were big ass analogue synths

Very illuminating, very usefull. I have a question at 23:17 the oscillation with a trinagle wave form now sounds smooth instead of broken. Does this mean you tuned a smooth sine and triangle for the sub mode instead of smooth triangle and sine for normal mode?

Tim, I really appreciate this video thank you so much. I have been playing around with the Model 15 app from Moog on my Mac / iPad and it's pretty incredible the sound you can get from these modules. I was playing around with the 921 oscillators for modulating the cutoff freq of the 904a -- such a wonderful sounding filter. The sine wave behaves the same as your behringer 921. It's great for neat moog specific sounding effects on modulation of cut off freq for example. I set up the output to aux out on the 921 and used the knob to switch waveforms and you can get such neat effects. I am thinking about adding the 921, 921A, 2 x 921B, 904A (filter), 2 x 911 (envelope gen) and 995 (attenutor x 3) to my Behringer System 100 rack. Would this be all I need? I can use the dual VCA from the System 100 right? I don't need the 914 fixed filter right now or a mixer module. The Model 15 comes with a 921, 921A and 2 x 921B for oscillators. And it comes with one 904A filter; also comes with two 911's. If you have the Model 15 app try the Trillibas patch.. sounds so good , great for techno; then modulate the freq of cuttoff with the 921 aux out.

Thanks Tim 👍

4:09 “Here I’ve got two oscillators, but I could have many” How many oscillators can we add?

Good thinking on the Clamping Point fix 👍 does that work at audio rate to let you create different timbres? 🤔

Hi Tim, awesome and infprmative as always! At 5:30 you describe linking the 921B's. Can anything like this be done with 112 Dual VCO's? Thank You

I have heard from an owner of a System55, who by profession repairs synths, claim the oscillators needed to be tuned and upon delivery of System55 unit to his residence were not prepared to make music. I have heard this same complaint about other synths from Behringer that go out of tune and need tuning that may only be done by professional repair or an owner that has above and beyond musician experience. What are the actual facts of the tuning of the System55? The tuning refers to the entire scale each note relative to the other, not just tuning to a concert pitch of 440Hz. (I have an Arturia synth that needs a 30-minute warm up and then needs tuned every time I use it, the tuning is a simple procedure, and the entire scale follows the "A" pitch tuning) (I also have a Korg synth that goes through an auto-tuning every time it is turned on).

my school owns an original system 55, it's been awhile since I've used it but I recall trying to make a really deep sub bass (30-50hz) and there were harmonics coming from the sine wave which I thought was odd, I pulled out my oscilloscope and sure enough until you get about 100hz or so it's pretty broken so yes, bob moog made weird stuff man

Many thanks Tim for your tutorial. Very informative served on easy way - as always. I have Behringer modules and I'm also experimenting with them, however I'm facing with a problem which is detuned 921Bs across the scale. Let's say I tune VCO to C2, but C3, C4 or C1 are not matching the tone.... do you have any idea for that?

Thanks!

Thanks a lot! I have a 921, and it's months that I'm wondering if I should buy another one or a 921b. Your video gives me much information, although I'm even more confused now :-) . I read somewhere that b's are way more unstable with frequency than 921's. What's your experience about this?

fan of Tangerine Dream, the Behringer 55 system interests me and your explanations are very clear and instructive. However, I hesitate between the Behringer 960 sequencer and the Erica Synths Black sequencer which seems to me more versatile, especially concerning racheting . What is your opinion ?

The Aion (brand) 921 clone does not exhibit this "broken" lfo situation. I just checked my Aions.

Great, it was what was missing. 921A/B and 921 difference. Greatings Form Switzerland -ArcSal

Hi Tim, what mics do you use on your videos? Specifally the lavalier one, I bought one and it sounded totally rubbish and yours always sound great. Thanks!

Tim, Very informative videos! I have recently received my system 55 and am having a problem. The notes do not release after releasing the key and the last note continues to sound just like what I am seeing in your video. How do I get the notes to release after releasing the key. Any suggestion to solving this problem?

LOL Tim, you looked like were using a green screen in your intro (because of the light behind!) :) Aside from that, I am still considering purchasing one of these (921B) in my ever expanding Eurorack (as per norm, lol). I have a Grandmother but the 921B is teeny weeny and sounds ace. What are the benefits of the 921A with the B, if I buy B would you recommend A as well is the question :)

Hello! I have a question, I have a complete system 55, when I put a Cv to the control input of the 904b and I get a note in the regeneration frequency (Almost sine wave) I try to tune the entire scale. but my 904b doesn't follow. The entire scale falls short, 1 and 1/2t almost below the octave. I have tried different CV sources. I don't know if I should do the entire scala in tune. Like Key tracking. Could you help me with your experience? Thanks!!!

Hi Tim. Thans for the video. I have two problemen with the 921B and wonder if that is normal? First: When I use the Range selector, the sound is not moving exactly one octave up or down? 2nd: I see you have the Range selector in audiomode on '16 in your video (I have to do the same) That gives already a very high sound. So its difficult to go down that much. Ofcouce I can go in sub mode but that behalen worden for audio level. A the same time the fine course is very much moving when you Just touch it. For me its too difficult to use on stage. Is it a problem with only my vco? Or do you have the same experience? Thans, Peter

The B921 in low mode has a significant step in the triangle and sine waveforms, unlike the original Moog. There is a minor slewing of these waveforms as you go low but the step is not correct and makes the 921 limited as a LFO. Not yet sure what the problem is, but its about how the low mode switch changes the triangle offset, which is controlled via an analog switch in the B921 rather than the Moog 3PDT switch.

Hi, how do you change amplitude of lfo on vco, since there is no any pot on input, like system 100,or arp2500 vco has? Your amplitude is always big

If I finally get around to visiting the UK, can I put you on my places to visit guide?

Do you plan on making a video about your Voyager XL at some point?

Now if only Behringer would clone the KB37.

Tim, if you put defiler envelope generator in instead of the behringer you will not believe your ears the deeper envelope generators are so snappy

Sounds to me like the pitch is warbling on its own slightly on those 922-b's.

do you know anything about ratcheting and if yes maybe you could make another very informative video ? just a suggestion, I bet many will want to see it

Is Tim aging in reverse?

The 921b was NOT designed as stand alone oscillator (in it's broadest sense of the word here) - this video here is an oversimplification, especially if you have synth voices with 2-4 units of 921B's as oscillator (also for PWM that you want ot be equal across OSC that form a synth voice as combination, and, as explained her by yourself a sa general tunning facility.

a 921 VCO vid and nothing about the scaling?

Sounds 👍🏻 but i dont like gabs !! Modular is soooo expensive GAS too No no no Dont want nothing else anymore System 100m (behringer) and 2600 (behringer) Sounds perfekt and The Fun i have with these is absolutly what i need to keep my GAS down . 🤣🤣🤣oh man . I‘ve got the wrong Hobby . I think i buy a flute tomorrow 🤣🙃🙃

Oscillators with half the waveforms… 😪