Adapting the EuroRack audio world for video synthesis

Discussion of modular and standalone video generating/processing techniques and associated hardware.

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lizlarsen
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Post by lizlarsen » Mon Aug 15, 2011 12:37 am

All the LZX module inputs are buffered before any attenuator circuitry, so it's kind of like having them built in. There is about a 0.05% drop in gain for each mult that's made. Using a buffered mult designed for standard frequencies in an audio system will limit the bandwidth of your signal, so in this case, passive mults or stack cables are preferred.

We may do a proper video-bandwidth buffered mult at some point, but so far it hasn't really been necessary taking into consideration how the modules are designed. Maybe in a really giant system where you wanted to feed an input video to 24 comparators at the same time, or something crazy like that, it would be useful.

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Post by PhineasFreak » Mon Aug 15, 2011 12:24 pm

yay! that's grand! i was mostly thinking for when i use midi to sequence stuff and i like to use velocity to control 4 or 5 variables at once - sounds like a good ol mult will do it.

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daverj
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Post by daverj » Mon Aug 15, 2011 2:07 pm

johnnywoods wrote:Dave: I'm curious about your earlier reply. Assuming your system runs on 0-1v video signals, does this mean CV inputs are separate from video inputs? Or is there some sort of switching to allow for the different ranges?
All of the input jacks on my video modules are dual purpose inputs. They are stereo 3.5mm jacks. The "tip" is a standard +/-5 volt CV input just like on any Euro audio/CV module. So any Euro module can be plugged into it and the video module sees it as a +/-5 v signal.

The "ring" connection of the stereo jacks accept my 2vp-p (+/-1v) video signals. All of my video modules take video in, and put video out on the ring connection of a stereo jack. So you use a stereo mini cable to patch video from module to module.

So basically you patch with a standard mono mini cable from any Euro module and my module sees it as CV or audio. Patch with a stereo cable from any of my video modules and my module sees it as a video signal.

So there are no separate video and CV inputs. All inputs accept either video or CV, depending on what you patch into the input jack.

The video input pins on the stereo jacks are terminated with 75 ohms, just like standard video. This allows a very high bandwidth, very low noise video signal to be passed between modules. Many of my modules have double outputs, so you can feed their output to two other modules without needing a buffered mult. I will also have a video buffered mult (distribution amp) module for when you want to go to more modules. (or to split signals from modules that only have a single output jack)

The 2v p-p video signal also helps reduce signal to noise by having a larger signal. Plus I have found over the years that a bipolar signal is nicer for mixing and patching because it centers middle gray at ground.

One other thing is that many of my modules have two input jacks for each input, which gives a mixer built into those inputs, allowing two video signals, two CV signals, or one video and one CV to be mixed at the inputs. Not all modules have that, due to size/space issues. But there are a number of them that do. This reduces the number of external mixers needed in the system. And allows easy mixing of video and CV.

My modules only put out video signals. The inputs accept either, but the outputs are video. A small module will be available to convert my 2v p-p video signals into +/-5v signals, but since the +/-5v Euro modules can't handle video rates, the result would be blurry video going out to standard Euro modules.

There will also be a small module to convert both ways between my 2vp-p signals and the LZX 0-1v signals.

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Post by MrDys » Fri Oct 21, 2011 10:24 pm

I mentioned early on in this thread (and elsewhere in this subforum) about my fondness for using the Doepfer A137-2 Wave Multiplier with video signals. I finally recorded an example of what it can do:

[video][/video]

It's really handy for modulating static images. I got the Video Ramps today and I can get a lot of motion out of just a few ramps -> mixer -> A137-2.

It's one of the cheaper Doepfer modules out there, so grab one.
darenager wrote:I wonder how many people with Maths don't know it can file a tax return, or that Plague Bearer can indeed give bears the plague
suitandtieguy wrote:STG IS ALL ABOUT THE PLUR.

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lizlarsen
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Post by lizlarsen » Fri Oct 21, 2011 11:14 pm

Oh wow, yeah great tip! That clip was awesome!! I want one now. We have a waveshaper design finished that can do interesting stuff, but specifically oriented towards polar-to-cartesian type conversion. It would complement that waveshaper nicely, to do the more video rate stuff.

Another great note about this is that any audio module can safely process the Ramps outputs without any bandwidth loss usually. The horizontal ramps are 15KHz, which is in the audio bandwidth range.

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Post by MrDys » Fri Oct 21, 2011 11:32 pm

Speaking of waveshapers, I had really good results tonight using the CGS/Ian Fritz 5pulser in a similar manner. I have a video uploading to Vimeo that somewhat shows it off (though not in a before/after manner like the clip above).
darenager wrote:I wonder how many people with Maths don't know it can file a tax return, or that Plague Bearer can indeed give bears the plague
suitandtieguy wrote:STG IS ALL ABOUT THE PLUR.

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lizlarsen
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Post by lizlarsen » Fri Oct 21, 2011 11:45 pm

Awesome. I'd love to see a demo like the one you posted, where the vertical signal you were viewing was used as PWM source on a horizontal locked oscillator so we could see the waveshape a little better, too.

We need to get a wiki going so we can start documenting all these notes!!

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Post by kjellb » Sun Oct 23, 2011 5:44 am

Personally I am very happy with toppobrillo wavefolder http://www.toppobrillo.com/TBmmCO/TWF.html

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Post by lizlarsen » Wed Nov 09, 2011 7:41 pm

Just got a Doepfer A-144 Morphing Controller and A-143-9 Quadrature LFO. Both are AWESOME for video!!! A-144 makes a 4-band soft-key colorizer for lower bandwidth signals (great in shape patches without a lot of fine detail) and A-143-9 can generate some very interesting modulation with all phase outputs controlling separate elements of a shape patch. I definitely recommend these two, especially for those of you wanting maximum utility in smaller systems.

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Post by nickciontea » Fri Nov 11, 2011 1:24 pm

i had the quadrature lfo in my case for a long time. only sold it planning to try the dr. octature from intellijel

Highly recommended

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Post by MrDys » Thu Nov 17, 2011 11:24 pm

The 143-9 is fantastic both as a modulator and as a video source. Super cheap, too. I may have to pick up another.

I wonder if it could be modded to have a sync input...

Edit: I asked on the Doepfer list if it could be modded for sync. Let's see what Dieter has to say.
Last edited by MrDys on Fri Nov 18, 2011 10:17 am, edited 1 time in total.
darenager wrote:I wonder how many people with Maths don't know it can file a tax return, or that Plague Bearer can indeed give bears the plague
suitandtieguy wrote:STG IS ALL ABOUT THE PLUR.

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lizlarsen
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Post by lizlarsen » Fri Nov 18, 2011 12:15 am

I can't say enough good about the 4MS Pingable Envelope Generator as a low frequency video modulation source. Having the separate slope/skew controls which are independent of frequency REALLY allows you to fine tune the response of an animation curve.
I'm also finding tons of more interesting uses for the A-144 morphing controller -- sending envelopes or slewed sequencer outputs into it before sending it's outs into a video patch is just incredibly useful.

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Post by MrDys » Tue Nov 22, 2011 11:21 am

Here's what Dieter wrote back Re: a A143-9 sync mod:
I'm sorry but that's not possible. We thought about this feature during the design but the circuit is kind of a filter in self resonance. If one would add a sync circuit similar to other VCOs (electronic switch that discharges the timing capacitor) the oscillation would not start with full amplitude but increase little by little until the full level is reached. That's probably not what you would expect from a sync input.

Best wishes
Dieter Doepfer
Oh well.
darenager wrote:I wonder how many people with Maths don't know it can file a tax return, or that Plague Bearer can indeed give bears the plague
suitandtieguy wrote:STG IS ALL ABOUT THE PLUR.

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daverj
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Post by daverj » Tue Nov 22, 2011 12:08 pm

If you have the Doepfer PLL module (A-196), You could try feeding video sync into one side of the phase comparator, feed one output of the A-143-9 into the other input of the phase comparator, and then feed the low pass output back into the CV input of the A-143-9. That might sync it up.

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Post by MrDys » Tue Nov 22, 2011 12:32 pm

I will try exactly that when I get home. I love this place.
darenager wrote:I wonder how many people with Maths don't know it can file a tax return, or that Plague Bearer can indeed give bears the plague
suitandtieguy wrote:STG IS ALL ABOUT THE PLUR.

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Post by MrDys » Tue Nov 22, 2011 10:30 pm

Yep. That totally worked. I feel like I've now greatly expanded my system with this simple patch.

Patch notes:
Video sync -> amplifier (I use half of a Gozinta) -> A196 "In 1"
One of the A143-9 outs -> A196 "In 2"
A196 lowpass out -> A143-9 CV1

The A143-9 should be set to the high frequency range. The Lowpass frequency on the A196 should be set fully counterclockwise. The phase comp type on the A196 should be set to 3.

You can put an LFO into the A143-9 CV2 to get accordion-style stretching animations with no problems. The CV knob must be set around 12 o'clock, though, for reasons I don't quite understand.

All in all, totally awesome. Thanks for the tip, Dave.
darenager wrote:I wonder how many people with Maths don't know it can file a tax return, or that Plague Bearer can indeed give bears the plague
suitandtieguy wrote:STG IS ALL ABOUT THE PLUR.

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lizlarsen
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Post by lizlarsen » Wed Nov 23, 2011 12:33 am

Awesome! That PLL module just moved further up my priority list.

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Matos
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Post by Matos » Wed Nov 23, 2011 12:38 am

Can we see some video? This sounds really cool. I've been looking at the pll trying to figure out exactly what it does. MrDys

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Post by MrDys » Wed Nov 23, 2011 4:54 pm

Matos wrote:Can we see some video? This sounds really cool. I've been looking at the pll trying to figure out exactly what it does. MrDys
Sure, I'll do a video over the long weekend.

Something Dieter said also triggered another experiment:
the circuit is kind of a filter in self resonance
Hooking this patch up to filters that can self-oscillate also works. It really depends on the filter, but I get very useful results out of the A106-5 and A107. I also tried the A106-1 and A127, but I think there's too much going on with those topologies for this to really work.
darenager wrote:I wonder how many people with Maths don't know it can file a tax return, or that Plague Bearer can indeed give bears the plague
suitandtieguy wrote:STG IS ALL ABOUT THE PLUR.

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lizlarsen
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Post by lizlarsen » Wed Nov 23, 2011 4:57 pm

This should work for most VCOs too!
I wonder if the A-196 is capable of line/hsync-rate sync'ing if the oscillator itself can go that high.

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Post by daverj » Wed Nov 23, 2011 8:18 pm

I would think so. A phase comparator is a pretty high speed circuit (usually a couple of flip-flops). I don't know about the filter in the A-196 (I don't have one), but you could always use a different low pass filter. And even with the current one, if it doesn't go high, the loop should still lock, but won't have a fast correction speed for quick frequency changes of the oscillator.

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Post by orangebud » Fri Nov 25, 2011 11:19 am

I'm using the Flight of Harmony Choices joystick. It's pretty handy because you get 2 rotary knobs for each input (scale/offset) that are quite powerful and then can use the joystick on top of it. Right now I'm routing a video in signal to one side of it and a some lzx VWGs controlling the lzx keying module to the other. I'm getting all types of colors/patterns quickly while the joystick is also acting as a fader for the video in out and as well keying.

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Matos
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Post by Matos » Fri Nov 25, 2011 1:38 pm

Yeah! I just plugged in the choices last night with the ramps to make some wipes and shapes blending different ramps. I'll have to see what else I can plug into it. Just nabbed a a144 based on your advice Lars. We shall see what magic it brings Monday.

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Post by lizlarsen » Fri Nov 25, 2011 2:40 pm

Cool! Yes, I have 2x Choices -- they are awesome. A144 would be great with Choices too. I imagine the Malekko/Wiard JAG would be super awesome as well, for lots of video stuff. I know it uses TL074 as the op-amp -- if I get one, I want to try increasing the bandwidth on it a bit.

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Post by barto » Wed Nov 30, 2011 2:16 pm

i got the chance to play with some Frac modules to experiment with integrating an audio input. We ran an ipod through a high pass filter and then to an envelope follower and then into the LZX and MVIP and got some pretty good results (ill post some vids soon). does anyone have any recommendations for euro modules that would do the trick? im looking at the doepfer a-121 multimode filter and the doepfer a-119 external input / envelope follower or possibly the doepfer a-170 dual slew limiter. orrr possibly wait until the LZX audio visualization module comes out? i do live video with DJs every now and then and would love to be able to plug in their audio into the LZX.

another thing that was fun was using a sequencer so if someone has a recommendation on that as well :tu:

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