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 » Wed Nov 30, 2011 2:21 pm

The A-119 would do the trick, if you don't want to wait for AV Tools. I use MATHS as adjustable envelope followers, too. You can also plug line level audio into the modules directly... nothing wrong with that, it is about the right signal range already (but there's no slope/envelope control of course.)

If you want filtering, a simple adjustable bandpass filter may be all you need, rather than a full multimode VCF but not sure what module(s) offhand would be best.

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Post by lizlarsen » Wed Nov 30, 2011 2:22 pm

For Sequencer, I use Pressure Points + Brains. The AV Tools has a beat detector output (so does the A-119, but it has no low pass filter), and at the Chicago meetup we were having lots of fun triggering the sequencer with the beat output.

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Post by nickciontea » Wed Nov 30, 2011 3:08 pm

every patch i make utilizes the Cwejman AP-1 for audio input/envelope. This is definitely overkill, but having the led meter is actually quite nice. I have come to recognize exactly where i typically want my signals amplitude at for the lzx.

In comparison to the doepfer.
the A-119 has the comparator out which could string a series of EG for more complex envelope following. Comparator outs also give you the ability to dial in and sync a sequencer to a 4 on the floor for instance.

AV tools big win is the individual bandpasses prior to the comparators so you get certain envelopes for certain frequency content (kicks, snares, lead)

Av tools will definitely be in my rig. but I also plan on buying the upcoming intellijel input module (w/ rise and fall EG and led meter) so i can give the ap-1 one back to its owner and save some hp and $

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daverj
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Post by daverj » Thu Dec 01, 2011 3:54 am

At the TV Center we used the envelope follower in an MS-20 for many years to drive video processing with audio. It works really well.

When we added Doepfer stuff a few years ago the first thing we added was the Vocoder Analyzer module, which puts out envelopes for a bunch of different frequency bands. I never got to spend much time with it, so don't know how well it really works for controlling video with audio, but I know a number of people that went through the Center used it.

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lizlarsen
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Post by lizlarsen » Thu Dec 01, 2011 10:23 am

The MS-20's ESP section is great! I heard a rumor that Scott/Harvestman is working on a modular version of it soon.

I have really enjoyed my AV Tools design, but I debate myself endlessly on preferring it (with the 8 filtered envelope outputs in 8HP!) or more of a single-channel in/out type thing with more controls like an adjustable bandpass filter and rise/fall adjustments.

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barto
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Post by barto » Thu Dec 01, 2011 8:41 pm

thanks all! would the A-119 and the AV tools be redundant or would they compliment each other? im thinking for the time being i could run my audio through a standard mixer and then into the A-119

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lizlarsen
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Post by lizlarsen » Thu Dec 01, 2011 8:43 pm

They are redundant in the sense that the AV Tools will do mostly the same things for you that the A-119 would (plus all its extra features). But there's no harm in having them both for multiple inputs! Plus, the AV Tools isn't available yet, is the main difference. :)

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lizlarsen
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Post by lizlarsen » Thu Dec 01, 2011 8:44 pm

I also highly recommend the 4MS Pingable Envelope Generator!! Two tap-tempo LFO/envelopes in one module. So awesome for quickly getting animation in sync with whatever a live band or DJ is doing.

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Matos
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Post by Matos » Sun Dec 04, 2011 2:11 am

Damn. Where is everyone getting these pegs from? Ah is on forever preorder. :ripbanana:

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Post by johnnywoods » Sun Dec 04, 2011 1:05 pm

Matos wrote:Damn. Where is everyone getting these pegs from? Ah is on forever preorder. :ripbanana:
Lars got his direct from Dan at 4ms. AH shipped a few, I believe, but when Dan announced the v2 upgrade, they returned them all to get upgraded.
I have two on the way from AH, and Shawn told me they should ship out early this week.

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Matos
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Post by Matos » Sun Dec 04, 2011 3:29 pm

Thanks. I'll see what's in my pocket when the vwg's arrive this week.

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Post by smrl » Sun Dec 11, 2011 4:20 am

Ian Fritz's 5-Pulser works beautifully with tri's & saws from ramps or a VWG. Input needs scaling to 5v.

Slew-rate limited in the lower-frequency x-axis region. Will probably try swapping out op-amps just to see what happens - I am considering building one of these pre-configured for 1v I/O, with higher bandwidth.

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Post by lizlarsen » Sun Dec 11, 2011 9:39 am

That's a really great idea! It looks like you could replace the op-amps with LM6172 or similar easily enough -- you'd want to also decrease resistor sizes by a factor of 10 or so (in addition to modifying for 1V scale.) The LM3914, I'm not sure how fast it is -- but it could be replaced by a string of other comparators if you wanted faster response (it's just more chips.)

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Post by smrl » Sun Dec 11, 2011 11:31 am

Yeah. It's a really simple idea for a waveshaper, especially with the bargraph IC having most of what you need already there. But it's definitely got me thinking - this is a really good way to get sync'ed oscillator-type behavior using just ramps and a control voltage!

But it all really comes down to how fast those comparators are on the chip... I'm going to do some modeling - I think this might make a useful subcircuit for a design! This would pair well with a variable slew since you've only got hard edges otherwise.

I'm doing some simulations...

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lizlarsen
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Post by lizlarsen » Sun Dec 11, 2011 12:23 pm

I like the way you think. Excited to see what you come up with! :tu:

And not every video circuit has to have 5MHz bandwidth either -- stuff that gives things soft edges can be nice, too.

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Post by daverj » Sun Dec 11, 2011 1:50 pm

The LM3914 was no doubt designed with very sow simple comparators, so I wouldn't expect much in the way of video speeds from it. Slow comparators don't put out soft signals. They put out signals with a lot of delay and no changes during detailed parts of an image. But they still transition relatively quickly. So they can give some interesting lo-fi look to video.

Of course audio op amps after them will then soften and blur the signal.

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Post by smrl » Tue Dec 13, 2011 2:04 am

OK -- This one's a lot easier than modifying a 5-pulser. I was messing around with the timing caps in my A-143-1. This could be very useful, I'm just not done messing with it to try further experiments. It's great as a trigger delay and/or ramp generator - Set one up as sync'ed to field, trigger another one with the comparator out of the 1st... Then with the 1st in A/D mode I could get many of the 'ramps' shapes (or approximations anyway), Or with the 1st in LFO mode, can get a bunch of bars with adjustable rise/fall slopes... Works great! Haven't even tried seeing what comes out of the mix output...

I simply subbed the 2.2u timing caps with 10/100nF. Will see how fast it can actually go, figure out some good values and then install a few switches to select. It seems as though this module is set up so decay values are up to twice what attack values are -- if I was using this as a module for exclusively video I would probably make this symmetrical.

This is also great for other things as well though! In the audio realm, running a square wave into the trigger gives you oscillator sync with variable timbre!

Also worth noting, I've used this module in the past as a trigger conversion tool -- because the comparator will trigger directly from the LZX I can drive a 4ms RCD/SCM with it.

If you've got an A-143-1, this one's too easy not to do!

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Post by lizlarsen » Tue Dec 13, 2011 2:09 am

Nice! I've got an A-143-1 and will have to try that. It's not very useful as an LFO to me, because of the non-linear slopes. This module also triggers decently off of just an external audio signal (like separated kick or snare drums) I've used it live in a pinch very effectively in that manner.

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Post by Matos » Tue Dec 27, 2011 12:56 am

So not really eurorack, but a great box that keeps on surprising me. The moog multipedal is great for animation. 4cv's that can be triangle, saw, square, random lfos or noise. All controllable by an expression pedal or by midi for tempo synced madness. You can save patches and switch between them via midi. Super rad to play the pedal to music and get all sorts of lush movements. It's my secret weapon in the war against static images. :bananaguitar:

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Post by MrDys » Mon Jan 09, 2012 7:06 pm

I've been using the Doepfer A-136 as a shape creator/animator. It can usually be picked up for next to nothing because people aren't particularly fond of what it can do for audio. Feed it a ramp and dial in the knobs as appropriate. Feed it some LFOs to get some movement out of it.
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 lizlarsen » Mon Jan 09, 2012 7:58 pm

interesting! from the picture of that module, it looks like it is two quad op-amps and a few passives? can you confirm which op-amp models they are? if there is a higher bandwidth DIP quad amp, it may be possible to swap them out for some increased bandwidth!

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Post by MrDys » Mon Jan 09, 2012 8:21 pm

Just checked, both are LM324N.
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 lizlarsen » Mon Jan 09, 2012 8:22 pm

I will dig around for any possible replacements. Paging daverj, do you have any ideas?

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Post by MrDys » Mon Jan 09, 2012 8:35 pm

Awesome. Out of curiosity, what would a larger bandwidth get me in something like a waveshaper module? A more detailed image?
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 » Mon Jan 09, 2012 9:06 pm

That's right. If you run video (like from a camera) through it now, I'd expect the output to be very blurry if not completely indistinguishable. The image would get sharper with higher bandwidth. This enables all sorts of exciting applications using this module to do colorizer/solarization type patches too.

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