Grayscale - Nexus 

Nexus brings the unique keyframing concept of Frames back to the Eurorack format. While retaining the same 18hp width as the original, Nexus provides eight more VCA channels, a faster workflow, an improved hardware spec, and numerous new features intended to provide an unprecedented level of control over complex modular patches.

Keyframing is a technique borrowed from digital animation. A keyframe marks the VCA levels of 12 different channels at a single moment in time. Up to 32 keyframes can be stored on a timeline, and the timeline position is controlled by a single large knob. When the timeline position is changed and levels vary between keyframes on the same channel, various interpolation algorithms may be applied to create smooth transitions between different levels. The timeline position can be controlled manually by turning the large knob, modulated by an external control voltage, or sequenced with a trigger source.

The open-ended nature of the keyframing concept makes Nexus incredibly versatile. With the ability to both process external signals and generate control voltages, Nexus can be used as a mixer, sequencer, LFO, envelope generator, attenuator, clock divider, sequential switch, stereo or quadraphonic panner, multi-channel crossfader, and more. Many of these functions can be patched simultaneously, providing extensive serial or parallel processing of audio and control voltages. This functionality can be further extended with new randomization options, including the ability to randomize keyframe levels and randomly step through keyframes using an external trigger source.

Stereo operation is simplified with individual mix outputs for each row (representing separate left and right mixes) and internal mono-to-stereo normalizations. The redesigned user interface allows for editing of multiple channels simultaneously, copying keyframes to new timeline positions, and saving up to 12 user presets. The core circuitry has also been upgraded to eliminate audio bleed and provide precise output level calibration. The VCAs are digitally controlled but the signal path remains entirely analog.

Frames vs Nexus

Operational Theory

The information below covers all features and functions of Nexus. Look for an updated user manual soon with more illustrations and patch examples. The 12 factory presets are currently undocumented, this will be updated soon.

Timeline knob. Turning the big knob scrolls through the timeline, controlling the rate of transition between keyframes. You can also modulate the timeline using the MOD input, which has a +/-5V range and a bipolar attenuator. When using external modulation, the 0V baseline is equal to the physical position of the macro knob.

Channel selection (SEL). The detented SEL encoder controls which channels may be edited. Turn the knob to select different channels. You can also press SEL to cycle through four different selection scopes (single, columns, rows, or all) allowing you to simultaneously edit multiple channels. When the selection scope is changed, the channel LEDs will blink to indicate the scope.

Level adjustment (AMP). The smooth AMP encoder adjusts VCA levels for all channels within the selection scope. Turn the knob slowly to make small adjustments or turn it more quickly to rapidly traverse the full range. You can also turn the AMP knob while it's being pressed to make very fine adjustments, useful for fine-tuning the pitch of a VCO for example. You may also press the AMP knob to toggle the selected VCAs between their minimum and maximum values. This allows you to quickly mute a VCA or open it completely without needing to turn the AMP knob. There's also a quick way to flip the levels of all channels within the selection scope. With the big knob pointing to a keyframe (KEY LED is green), press VAR. All channel levels within the selection scope will be flipped. Press VAR again to revert this change and flip the channel levels back to where they were previously.

VAR switch. Performs various functions, often in combination with pressing or turning other controls. See the other sections for documentation of all VAR functions.

10V switch. In the upper position, enables an internal 10V DC offset which is normalized to any unpatched inputs. This allows Nexus to generate CVs by internally modulating the channel VCAs with the DC offset. In the lower position, the DC offset is disabled.

Channel I/O. There are 12 channel inputs with an associated LED indicating the VCA level for each channel. Below that are the 12 channel outputs which mirror the inputs and their post-VCA processing. The top row of inputs (odd numbers) is normalized to the bottom row of inputs (even numbers) so that mono signals can be easily converted to stereo. Or you can patch existing stereo signals into the odd/even input pairs.

Add/delete keyframes (KEY). One of the "key" concepts to understand is that VCA adjustments can only occur on keyframes. To add a keyframe, turn the big knob to any location along the timeline. If the KEY LED is off, press the KEY switch to create a new keyframe. At least two keyframes are required—otherwise there is nothing to interpolate or sequence—so turn the knob to a second location and add another keyframe. Now you can set up the individual VCA levels for each channel. To delete a keyframe, point the knob to an existing keyframe (indicated by a green KEY LED). Press the KEY switch and the KEY LED will turn off, indicating that the keyframe has been deleted.

KEY output. This output generates a 10ms trigger whenever a keyframe becomes active, like the FRAME output on Frames but with a different label.

ODD/EVEN mix outputs. There are separate mix outputs for each row, labeled ODD (odd-numbered outputs) and EVEN (even-numbered outputs). In a stereo patching paradigm these could also be considered LEFT and RIGHT outputs. Patching a cable into any of the individually-numbered outputs will subtract that channel from the mix output on that row. Keep in mind that you can patch the mix outputs back into an unused pair of channels to perform further processing, then patch the individual outputs for those channels out to an external mixer, headphone amp, etc.

Interpolation types. Each channel uses one of six interpolation types during transitions between keyframes. Press the VAR switch and then turn SEL to choose the interpolation type for all channels within the selection scope. The KEY LED will turn orange during this process and the channel LEDs will display an animation of the interpolation. The six options include linear, exponential (ease in), logarithmic (ease out), sinusoidal (ease in/out), or two non-interpolated stepped modes. Step A works like the "stepped" mode from Frames, where the transition occurs at the halfway point between two keyframes. Step B applies the transition whenever a new keyframe become active.

VCA response. This setting controls the "feel" of the AMP knob (ranging from linear to exponential) and how the VCA responds to the interpolation curves. Press the VAR switch and then turn AMP to adjust the VCA response. The KEY LED will turn red during this process and the LEDs for all channels within the selection scope will display an animation of the VCA response. Unlike the six discrete interpolation types, the VCA response is more of a smooth crossfade between fully linear (turn left) and fully exponential (turn right). The range covers approximately 1.5 full rotations of the encoder.

Copy keyframes. This feature saves time when you want to set up various keyframes that modulate to/from a common baseline. Point the big knob to any existing keyframe (KEY LED turns green). Press the KEY switch for a few seconds until it turns red. You have copied the existing keyframe. Now turn the big knob to the timeline location where you want to create a new keyframe. Timeline locations with no existing keyframes are indicated by an orange KEY LED. Pasting into those locations will create a new keyframe. Timeline locations with existing keyframes are indicated by a red KEY LED. Pasting into these locations will overwrite an existing keyframe. If you want to exit the copy/paste mode without changing anything, press VAR to exit.

Randomize VCA levels. With the big knob pointing to an existing keyframe (KEY LED is green), press and hold the VAR switch for 3 seconds. The levels of all channels within the selection scope will be randomized. Repeat the process to randomize again.

Sequencing modes. Once you've set up your keyframes, there are three ways to move through the timeline. You can select one of these three options by pressing the SEL knobs for 3 seconds, then turning it. The KEY LED will start to blink, showing one of three colors to indicate the current mode. Green is the linear mode where keyframes can be smoothly interpolated by turning the big knob or patching external CV into the MOD input. Orange is the sequencing mode from Frames, where a trigger patched to the MOD input will step through keyframes without interpolation. When using this mode you can turn the big knob fully to the left to "reset" the sequence to the first step. Also be sure to turn the MOD attenuator up so that the trigger will be received. Red is the new random sequencing mode, which works like the orange mode but keyframes are selected randomly instead of sequentially. Once you've selected the mode you want, press the SEL encoder or the KEY switch to lock in your selection. Pressing VAR will exit without changing the mode.

Save presets. Press VAR and KEY for 3+ seconds. The KEY LED will start to blink green. This color indicates the SAVE mode. Release both switches once the LED starts to blink, then turn the SEL encoder to select one of the 12 preset slots (indicated by the channel LEDs). Press KEY to save the current keyframes, interpolation curves, and VCA response settings to the selected preset slot. Or press VAR to exit without saving.

Load presets. Nexus ships with 12 useful factory presets (not yet documented!) or you can also load presets that you've saved over the factory presets. Press VAR and KEY for 6+ seconds. The KEY LED will blink green after 3 seconds but will turn orange after 6 seconds. Release both switches while the LED is orange, then turn the SEL encoder to select one of the 12 preset slots (indicated by the channel LEDs). Press KEY to load the preset from that slot. Or press VAR to exit without loading, preserving your current keyframe config.

Delete all keyframes. If you want to quickly delete the current keyframe config, deleting all keyframes and returning all channels to their default interpolation/response settings, press VAR and KEY for 9+ seconds. The blinking KEY LED will cycle through green, then orange, then red. Release the switches once the LED turns red, then press KEY. This will delete all existing keyframes. All channels will be assigned the linear interpolation type and linear VCA response. This operation does NOT affect any presets—only the working state of the module.

Delete all presets. There is an additional operation that you can perform instead of just deleting the current keyframe config. After pressing VAR and KEY for 9+ seconds, the KEY LED will start to blink. Instead of pressing KEY to delete the current keyframe config, press the SEL knob once. All 12 of the channel LEDs will start to flash, indicating that all of your user presets are about to be replaced with the 12 factory presets. Press KEY to confirm the total annihilation of your carefully-crafted presets. Or press VAR to exit, keeping all of your presets intact.

VCA calibration. When you move the module into a new case you may need to calibrate the VCAs. The module is calibrated at the factory but some modular power supplies put out slightly more or less than the optimal voltages. This will throw off the 0V baseline for the module. You may notice for example that the channel LEDs light up even when the VCA levels are set to zero, or that the channel outputs do not generate precisely 10V when the switch is enabled. This indicates that you need to perform calibration. To do this, power up the module with the VAR switch pressed, and make sure that none of the module's inputs (especially the MOD input) are patched. The KEY LED will blink green/red. The MOD input auto-calibrates itself immediately and this may be all that you need to do. Press either the VAR or KEY switch to save the calibration data and continue using the module as you normally would. But in some cases you may also want to recalibrate the individual VCAs. To do this, enable the 10V switch (up position) and measure the output of channel 1 using a multimeter or a module like the Mordax DATA. Turn the AMP knob until the multimeter reads as close to 10.000V as possible. Then turn the SEL knob to select another channel, patch that channel output into your multimeter, and repeat the process until all 12 channels are calibrated. Once the calibration is complete, press either VAR or KEY to save the calibration data and get back to patching.

LED brightness. Depending on the ambient light conditions you may want the 12 channel LEDS to be dimmer or brighter. Press the AMP knob for 3 seconds to change this. The KEY LED will flash red to indicate that this mode is active. Turn the AMP knob to choose from one of eight brightness levels, then press either the AMP knob or the KEY LED to save your preference. Pressing VAR will exit without changing the brightness.