Reference Manual
Topogram
Technical documentation, setup guidance, and patching workflows.
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Archived community reference. This page preserves the official LZX Community forum thread for Topogram inside the new documentation site.
Additional related discussions are included below.
Topogram is a sequential soft key generator capable of splitting live video and patterns into discrete bands for colorization and control. Edge transitions feature voltage controlled gain for creating hard edges or smooth gradients. Upper and lower thresholds for the keying range may be voltage controlled separately.
- Topogram takes simple inputs and slices them up. Six non overlapping regions can be patched out for 6 band colorizer patterns, along with another 8 outputs which group and span multiple ranges.
- Driven with LFOs and low frequency envelopes, Topogram becomes a frequency independent sub-event generator for animation control of your patch.
- Topogram features elevated technical and performance specifications, and is the result of years of research and testing of discrete analogue video circuitry. The signal path is fully active, and CV attenuverters have a deadband range in the center. The circuit is entirely analogue.
Specifications
- Width, 16HP
- Mounting Depth, 32mm
- Power +12V @ 200mA
- Power -12V @ 200mA
Videos
Other Resources
Thread Replies
Just received my new Topogram! Just checking - this module doesn’t include the quick-start user manual / guide, correct?
Correct. Congrats on finding one!
Another few patching nuggets from FB thread for the archives:
[Lars Larsen]
patch a single luma video source into “input”, then patch as many outputs to as many colors as possible-- going to all 6 inputs on Cortex then setting up an additive blend is a good way to get plenty of variety. set the left knob low, the right knob high. try modulating the gain with a video pattern – very unique function in this case, like modulating 5 doorways in parallel.
[Robin Burke]
Send all 6 outs from the Topogram to two Passages & then bring a Senory Translator & other modulation sources into play
[Luix Bot]
feed it a lfo (like pendulum 0v-1v) and convert it into complex multi output LFO
[Nichole Pichon]
use the thru output as feedback into the gain/upper/lower inputs
polar fringe pos/neg key outs into the upper/lower inputs makes for a crazy colorization patch basis
topogram thru output goes into doorway source in
premixing video with slow strobing CV before going to topogram input
U/V outputs from mapper into upper/lower ins. Y from mapper into source of topogram
we use a reverselandfill matrix mixer to mix 4 outs from the topogram together.
sensory translator + topogram outs going into a passage is great fun for audio reactive patching
If I were theoretically able to get my hands on a Topogram, would it have enough bandwidth to handle 1080i and stay reasonably sharp?
And will there be a Gen3 equivalent? Looking for a multi-zone CV keyer in the vein of the EAB Videolab, with the ability to plug external video and/or voltages into each zone. I know about the proposed posterizer from Reverse Landfill. Hoping for a module that can handle RGB sources, although I know that’s a big ask. Such a beast would not fit into a Gen3 form factor. It’s just that I don’t relish the thought of three separate modules – keeping hard key zone edges aligned while under CV control might be impossible.
For reference, here is the sort of thing I want to achieve
(EAB Videolab II + Fairlight CVI)
Warning: intense strobe / epileptic seizure risk
Yes. Twenty additional characters to make the forum bot happy.
Cool beans. If one becomes available I may snatch it up, unless something better is announced.
this might be interesting to your search!
“Solarium”
Video Colorizer & Sequencer
Inspirations: classic multiband keyer/colorizers, Topogram, Marble Index, Video Blending Matrix, Amplitude Classifier.
so this is not set in stone at all in fact the “road map” has had a bunch of deviations from the looks of it already. However topogram being listed as an inspiration is a good sign. So look forward to some kind of automata “video colorizer” that will at least pull some inspiration from topogram.
Yeah!! That sounds epic. But it won’t be soon.
Fantastic news, I scored a Topogram on Reverb.
Is there more documentation other than what’s on this page?
To turn Topogram into a full-blown colorizer, my plan is to patch the outputs into 2x SMX3, and then sum the outputs of the SMX3s. Is this a viable plan?
This is all of the documentation currently available for Topogram. 2x SMX3 would be a great destination for all of Topogram’s outputs.
Related Archived Discussions
A Keying Dictionary
Describing the diverse range of activities in a video synthesizer that involve the word key can be a challenge. Here’s a list of definitions that we’ve used – this is certainly not the only way to categorize or apply these terms, but I hope it makes the intentions behind our own usage of them in relation to LZX modules clear.
- A key is any video signal used to control a transition between two or more other video signals. As such, any signal patched to a key input becomes a key.
– A hard key is a boolean logic signal which switches between two signals.
– A soft key is an analog voltage representing the mix ratio between two video signals. - A key generator is a module designed to condition an input for the purpose of keying operations.
– A hard key generator is typically implemented as a differential analog comparator.
– A soft key generator is typically implemented as a high gain differential amplifier with black and white level clipping.
– A chroma key generator processes the chroma components (PbPr) of a component video signal, allowing key extraction based on Hue and Saturation of the video source.
– A luma key generator processes the luma component (Y) of a component video signal, allowing key extraction based on the overall brightness of the video source.
– A component key generator acts on one color channel at a time, but still includes the entire colorspace in its output function. For example – a red component key is active when areas of red appear in the image in the absence of any green or blue.
– A multi level key generator produces multiple key signals from a single source, and are often used as the frontend for colorizers and sequencers.
– A window key generator has dual threshold controls, either Upper/Lower or Span/Center - A fader or switcher is a module which performs a transition between two video sources. Typically it has a direct key input, without much local control over the key itself.
- A keyer is a module which has both a key generator and a fader or switcher. Typically the output of the key generation function is tied directly to the driving circuitry for the fading or switching function.
- A linear colorizer or multi level keyer combines multiple faders with a multi level key generator function to produce a transition across more than two inputs. If we feed static color offsets to the inputs, and drive the key input with a video source, this is a linear colorizer. If other video sources are used instead, it becomes a sequencer or compositor.
To drill down on some of the relational terms:
- A keyer is both a key generator and a fader.
- Keying is always fading, but fading is not always keying.
- Any signal can be a key, even those not processed by a key generator.
- A key is created whenever any connection is made to a key input.
- Keying is what is happening to a fader’s input signals when the fader is controlled by a key. At the fader’s output, are the keyed results.
And, to apply these to various LZX modules:
– Triple Video Fader & Key Generator (Visionary Series) is a triple hard key generator + triple fader. Due to its semi-modular signal flow, it can be also used as a single hard keyer for RGB signals.
– Cadet VIII Hard Key (Cadet Series) is a single hard key generator.
– Doorway (Expedition Series) is a single soft keyer.
– FKG Keyer (Gen3 Series) is a single RGB/Luma soft keyer.
– Topogram (Expedition Series) is a five band multi-level key generator.
– Visual Cortex (Expedition Series) contains an integrated single hard keyer / output encoder.
– Polar Fringe (Expedition Series) is a soft chroma key generator
– Memory Palace (Orion Series) contains a discrete digital implementation of a soft window keyer
– Keychain is a triple hard key generator
Please let me know if I can help clarify or further define the language we’ve used in this context.
If this seems overwhelming I wouldn’t worry about memorizing all these terms – these are complicated ways to describe something that’s already probably intuitive to you if you patch the system. This post is here to serve as a disambiguation guide, so that it’s clear what’s meant across a history of different modules, different series, and different approaches to keying.
Thread Replies
I’m now going to have this in my head all morning…
I’ve got the key, I’ve got the secret
I’ve got the key to another way…
regarding the window key what kind of math is used for the span/center controls?
what kind of math is used for the span/center controls?
You need a Span/Center processor that generates the Upper/Lower thresholds.
Upper Threshold = Center + (Span / 2)
Lower Threshold = Center - (Span / 2)
Is there any reference circuit for this implementation? Would be interested in breadboarding something!
Thank you for posting this Lars!!! Luckily we have lots of keying module options but sometimes not all transparent regarding the specifics of each? Wondering if a spreadsheet with all the differences or overlap would help? Nonetheless this post helps clarify differences. I think I have all the ‘keys’ for now so I’m good. 
Can we add to the list above?: “Keychain” (Gen3 Series) is a triple hard key generator.
I haven’t published a reference circuit, but a block diagram is fairly straightforward.
Here’s how I do it after trying many ways:
I tried lots of specialty high gain parts or integrated high gain VCA parts that were expensive and troublesome over the years. What works best in the end is just doing multiple stages after the VCA block, with 4x - 5x per gain stage, and use a separate op amp per stage. Two 5x stages in series it gives you a total gain of 25x, which gets a decently hard edge without going too crazy (this is about where Topogram sits for example.) Cadet II RGB Encoder is a good reference for a precision Black/White clipping circuit.
Thanks so much for sharing this, very helpful!
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