Conversion to LZX RGB format

You want a USB-to-CV interface that can be calibrated on the software end to output a 0 to 1.0V scale. Check out the products by Expert Sleepers.

2 Likes

This is what we are planning presently. It is a 4-channel voltage attenuator/amplifier with 4x buffered outputs per channel (so you can guarantee identical impedance.) This covers the standards you mentioned. There is no unipolar to bipolar conversion and back – but that’s not usually an issue in context. +/-1V signals and double gain +/-2V are part of the LZX standard too, as of Gen3.

Analog processing tolerances will sit around 1% to 2% of nominal (we use 1% resistors throughout all the builds.) I’m sure the tolerances on the Scanimate were much worse. But repeatability? You can get that. Just have attenuverters fully clockwise or counterclockwise and use a precision USB-to-CV interface as mentioned above – and you can micro-tune your voltage in software.

Another mention is that the ESG3 module has trimmer adjustable RGB Gain + Offset levels. So with that as output encoder, you can always calibrate the color balance across multiple outputs.

4 Likes

Thanks, I was planning on getting an ES-9 when it’s available again… wasn’t sure how configurable the outputs are, but it sounds like it will do what I need.

That looks great! So to convert 10V to 1V I would need to use two channels of the Quad Amp?

+/- 2V is news to me… what is up with that? Why? Where?

Fantastic! All great news!!!

1 Like

This would be in cases where you want to overdrive the parameter range. Think of it like +/-200% as opposed to +/-100% or 0 to 100%. For example, the SMX3’s attenuverters go to +/-200% scale so that you can convert from YUV to RGB and back again. YUV to RGB requires some gain beyond 1.0X to reach full scale.

It’s also the available minimum headroom on any module (meaning you can always patch up to +/-2V to an input without clipping before attenuation.) So in other words, if you can get your external voltage down to within +/-2V, you can patch it around the system without losing any part of the signal. The FKG3’s RGB inputs for example – they could switch between +/-2Vpp signals on the foreground and background if desired.

Another example is to think of say a vector based parameter like “width”. We may want the range to be 0% to 200%, or “nil to 2X”. For math reasons with four quadrant multiplier circuits we may want the following to be true:

1.0V * 1.0V = 1.0V (unity gain)
2.0V * 2.0V = 4.0V (clipped/amped behavior)

2 Likes

Yep! We haven’t committed entirely to this layout yet. Another option would be swapping a channel or two in exchange for rotary switches that allow more settings and offsets. But if you can gang channels for other ratios… are we just removing channels for no reason? “Channels per HP” is the currency to consider. We want to see what users think after playing with the first set of modules before making any final decisions. This seems like a balanced solution for both signal distribution and conversion that covers most user needs to myself, at the moment. But I generally work exclusively within the LZX ecosystem personally, so I may not be the best arbiter of use cases here.

1 Like

Here’s another interesting case for bipolar signals. Since ESG3 lets you set a “default RGB gain/offset” with trimmers, you have the ability to tune your system to alternate ranges and standards in a new way.

For example, for 0V to 1V = RGB type behavior, you would trim the offsets to 0V (black) and the gains to 1X (which sets 1V = White).

This method preserves this assumption: WHITE - WHITE = BLACK and BLACK + WHITE = GRAY.

This is Metallica style (fade to black.)

For +/-1V = RGB type behavior, you could trim the offsets to +0.5V (50% gray) and the gains to 0.5X (which sets -1V = black and +1V = white.)

This method preserves this assumption: WHITE - WHITE = GRAY and BLACK - BLACK = GRAY.

This is Visage style (fade to gray.)

Many vintage video synths (for example the Sandin IP and most of Dave Jones’ instruments) used bipolar signals and were more Visage style.

Since at LZX we mostly listen to 80’s metal, we defaulted to Metallica style in the early days. Also, we wanted to preserve the type of RGB math relationship used in compositing and RGB graphics – where RGB is an unsigned integer from 0 to 255 or 0 to 1023, etc.

While Metallica style is more accurate / useful if you are doing math with colors – there are benefits to Visage style. If you mix bipolar signals in a summing bus for example, each will end up increasing/decreasing contrast relative to each other while keeping median brightness consistent at gray instead of additively boosting “exposure” with each additional source in the mix. I’m certain in a future blending/compositing module, we will have the two approaches as different modes.

Of course on ESG3 you can get to both places with adjusting the control knobs directly – it’s just being able to trim those null spots to different places that is a new functionality.

6 Likes

On that Quad Amp mockup, it looks like each channel has one input and four outputs. I would be quite happy with more channels or more controls, I would just use a mult module or stacking cables if I needed more outputs. I also would prefer not to gang channels together, that cuts the number of signals in half.

So for me at least, I’d prefer four channels, each with:

  • one input

  • one output

  • two position toggle switch for multiply or divide
    (no need for neutral setting if no mult function)

  • rotary switch for multiplier/divider value, with at least these options: 2, 5, 8, 10
    (apparently some manufacturers, e.g. Noise Engineering, use 8V)

  • three position toggle switch for DC restore: bipolar to unipolar, neutral, unipolar to bipolar

Thanks

2 Likes

I like your Metallica / Visage analogy.

I can tell you that the Sandin IP was a real pain to work with in that regard. I absolutely hated the bipolar scheme. HATED IT

2 Likes

The intention is that this is both the system’s quad active mult and it’s quad amplifier/attenuator (with presets). Think of it as straddling both functions (which are essential, core functionality for a modular system). We found this worked well in patching context on our Bridge module – usually if you’re level translating an external signal, you want a mult at the same place (to distribute through your patch.) Also, many cases where you are using an active mult – preset gain modes come in quite handy (like overdriving a video source to create a distributed soft key.)

The 2-in-1 nature here serves another purpose: a voltage scaler may not be used in all patches, but a dedicated mult is almost always going to be in use. So this is a currency in our design guidelines – we want every HP worth of module to be useful in as many different patches as possible, even when they play different roles. It’s a big ask, to pay a lot for a module with some preset voltage scalers on it, so we try to overlap things in a way where the module can pay it’s rent in multiple ways. That’s my thought process in any case.

Unless arranged in rows instead of columns, the inclusion of rotary switches would require that this be a three channel (instead of four) module. You can see the formula I’ve developed for Gen3 ergonomics here so you can see the constraints more specifically (this example shows SMX3 – 9 knobs, 12 jacks):

two position toggle switch for multiply or divide (no need for neutral setting if no mult function)

Agreed on this point if we excluded a mult – however it’s worth pointing out that a 3-position toggle is essentially “free.” That is, no extra panel space and negligible extra parts cost to go 2 instead of 3. Some controls are of course, binary by their nature and a third position could be confusing.

A three position “bipolar to unipolar / bypass / unipolar to bipolar” toggle is something I had on an earlier mockup. I think that’s a good idea, especially if we drop some mults.

Another alternative to mult outs are complementary outs (positive and negative.) For example, we could drop 2 outs in favor of this. This would be a similar layout then, to DSG3, if combined with a polarity mode (12x toggles, 12x jacks)

Dropping the mult outputs – adding the complementary outputs – we could have a third range setting on the amp level. For example, 2X, 5X and 10X. This could work, but then we need a separate module as the go-to active mult (not really an issue, but if you are trying to make a small system it makes it more difficult, if you need both functions.)

These are just designer musings – not necessarily a defense of the existing configuration. This is actually a great case where soliciting user feedback before we commit to a design is a good idea.

2 Likes

Love it. That would be genius.

1 Like

I guess so long as we’re brainstorming… one thought is that the gain levels (2X, 5X, etc) are trimmable by the user, and are instead more of “Setting 1” and “Setting 2”. That way you can null out any tolerance stackup and they can be recalibrated to any desired voltage standards. So they could be 1.8X and 8X instead, and also you could calibrate channels differently. This would be starting to add the kind of value that might justify a dedicated module (without mults.)

2 Likes

I guess you could add tiny tweaker trim pots. Calibration would require a scope or multimeter, though… not sure how popular that would be.

2 Likes

Well I reckon they’d be pre-trimmed to the 2X and 5X defaults, and likely never touched (so it’s more of an advanced user recalibration thing, accessible from the front but under the panel – like the XYZ trimmers on Chromagnon and the RGB trimmers on ESG3.)

If you have very precise scaling needs – or a scaling need for something uncommon, legacy or odd – like an 8V envelope or a +/-10Vpp LFO, or a vintage Buchla – or you need incredibly tight results (like you need that V/Oct keyboard to open and close a key precisely in 5ths, etc) – it could come in quite handy and prevent dead ends or redundancy in the system design.

And I don’t care about popularity so much – Gen3 can have some modules that are less popular, we’ve designed the supply chain where a module that may be “academically important” can still have a place even if it’s not a hot seller. Biggest things for me are functional value and usability, from folks exactly like yourself – artists allocating their hard earned budgets to tools they need access to.

So given that voltage scaling is a common need, whatever the first Gen3 module in this category is, it needs to cover the widest range of use cases for artists out there.

2 Likes

@creatorlars i haven’t read through this whole thread yet but wanted to add a +1 for swapping switches for rotary knobs that allow more configurable settings. Switches are great in an either/or this/that situation but if there is any option for more configurable settings I would love to see rotary knobs to allow for that.

Even better-control voltage inputs - which so far seem to be missing from the Gen 3 modules we have seen so far.

They’re all control voltage inputs! If you need to vary the depth of modulation on any input, patch them into a VCA or crossfader beforehand or sum your input signal with another modulating signal to bias a parameter up/down.

1 Like

@rempesm yeah. True. I understand this but personally I like the option of discrete (per function) modulation inputs for voltage control over manual switches, but this seems to be a distinct design choice which differs a bit from the expedition series and I appreciate that others may prefer hands on playability.

1 Like

Maybe its just a patching style thing?

1 Like

That makes sense. Adding VCAs (or ideally 4Q multipliers!) to every input can ease spontaneity in patching but they will necessarily add to HP and overall cost per module. “You can never have enough VCAs” is probably even more of a truism in video synthesis since they often determine where your signals appear, allowing for denser compositing approaches.

This can be quite a cool effect if you use video rate signals to alter where on the screen a module is switched into one mode or another (kind of the inspiration for SHUTTER, I’d say). I think that could get really darn confusing with a fixed voltage scaler, though. The module above seems very utilitarian in nature.

Oh for sure. There’s no ‘right’ way to patch these instruments up. I just happen to mix and mingle most of my signals with intermediary mixers and VCAs.

1 Like

Maybe its just a patching style thing?

Not really – it’s more of a functional identity and design-your-own-workflow thing. Think of it in terms of modality. The switches are setting the module – or in this case channel’s – mode or state. If you have four identical channels, you can switch between their outputs to create whatever modulation scheme you can dream up. If we’re talking “how much can I do per HP” then this is wildly more powerful and flexible than giving each toggle switch a CV input.

This is not new – for example, you can compare DSG3 to Visual Cortex’s Ramp Generator section pretty directly.

The modulation happens on the outside of that – for example, DSG3 has two identical shape generators. Patch one to FKG3 background, and the other to FKG3 foreground, and what you’ve set up is a voltage controlled fade between two different groups of settings. Now in 24HP you have a “programmable RGB shape morph”, creating a kind of super module where you can design whatever kind of CV modulation you want. This becomes quite deep quite quickly. You want to control a transition from star to circle? You can do that fast and easy, even after you’ve set up your patch, just by flipping the switches on either side of the transition.

If we were to put CV controls on the DSG3 (and sacrifice one of the channels as a result) you end up with a shape generator with voltage control – but it’s not capable of nearly the same range of functionality as the DSG3 + FKG3 combination would be.

So it’s not that we’ve dropped CV inputs (they are there! on FKG3, and DWO3), it’s that we’ve introduced the idea of more multimodal modules.

With Expedition series there is a lot redundancy with certain CV inputs. For example, Marble Index’s CV inputs + attenuverters are handy for more abstract use, but redundant in the case where you’re patching in a key (in this case, the key generator itself would have already set the control range.) This makes it more difficult to use the module for it’s intended purpose.

So to sum all this up, it’s all about ratios: You’re the one in control of how much CV modulation your system has! If you want lots of discrete transitions, go heavy on FKG3s and lighter on the other modules. If you want more programmable settings, go lighter on the keyers and switchers and heavier on modules with programmable modes.

Consider the toggle switches less as “parameters to modulate” and more “several modules in one, which one do I pick for this patch?”

4 Likes

@rempesm thanks for your notes and perspective. Always a pleasure.

@creatorlars this insight on the design and conceptual patching structure is a great help with approaching a patching mindset with gen3 and quite honesty a nice overall take in thinking about things from an angle I hadn’t full considered before. Always an educational experience (why I love this medium)

4 Likes