KEYCHAIN

Keychain extracts sharp-edged stencil shapes from video images or patterns. It generates hard keys in standard or high definition using voltage comparators with a response time of only seven nanoseconds!

One of Keychain’s killer apps is generating animated wipe patterns from grayscale gradients. The simplest example is a ramp, or a mutated ramp from a pattern source such as DSG3. But any grayscale image is fair game, so go wild and crazy with novel, unique, and unexpected wipe shapes!

Keychain is also useful for processing low frequency signals such as LFOs and noise sources, converting any waveform into a square wave or variable width pulse. This is useful for animating hard cuts of varying durations with modules such as Switcher.

Keychain’s outputs can be used directly. For example, Keychain’s outputs can provide RGB channels to ESG3. In combination with ESG3’s proc amp controls, this simple patch is a three-level posterizer.

The full power of Keychain is unleashed in systems that include other core modules, such as DSG3, SMX3, DWO3, and Proc. Keychain is an essential building block of more complex patches involving layered imagery and/or instantaneous transitions such as hard cut edits.

Keychain consists of three independent channels, 1, 2, and 3.

Each channel outputs a one-bit signal with values of zero or one volts.

Each channel has two inputs, one labeled CV and one with a Key icon. The threshold of the key is set by the combination of the inputs and the Thresh potentiometer knob.

The gain of each CV input is adjusted with its attenuverter potentiometer knob, labeled CV. At the twelve o’clock position, the CV signal is multiplied by zero, nullifying it. Turning the CV knob clockwise, to the right of 12 o’clock, increases the CV gain up to its full intensity. Turning the CV knob counter-clockwise, to the left of 12 o’clock, inverts the incoming CV signal.

Both sets of inputs are internally self-normalled, allowing a signal patched into a channel 1 input to flow to the corresponding inputs of the other channels.

Internally, each Keychain channel consists of a mixer and a comparator. The mixer architecture is similar to Proc. A signal patched into a Key input is passed to the mixer without adjustment. A signal patched into a CV input is multiplied by its attenuverter potentiometer before being passed to the mixer. These two inputs are summed along with a third signal: a static voltage controlled by the Thresh potentiometer knob. Unlike the Bias control on Proc, the Threshold control is unipolar, ranging from zero to +1 volts.

 <br />

The output of the mixer goes into a lightning-fast comparator that slices the signal into two states, on or off. For video signals, this means different areas of the frame are rendered as matte values of zero or one volt. For low frequency signals, it means sudden transitions between black and white.

 <br />

3 Patches for Keychain <br />presented by Johnny Woods

For a hard key composite of two sources, send a Keychain output to the CV input of a crossfade module, such as Bridge or VH.S Crossfade.

Sending a Keychain output to PGO gives perfectly phase-aligned positive and negative alpha channels. This unlocks new achievements with mixers such as Proc and SMX3, turning them into hard keyers!

Since Keychain’s inputs are internally normalled, it can generate three keys of different thresholds from the same source. One application, a three-level posterizer, uses the ABS outputs of DSG3 to create discrete, non-overlapping bands of values. Each band goes to a top row input of SMX3, giving independent control of RGB or YIQ colors.

<table>

<tr><th> </th><th>Connectors</th><th>Controls</th></tr> <tr><td>

</td><td>

</td><td>

</td></tr></table>

Keep your module free of dust and debris by performing periodic cleaning. Spots may be cleaned from the frontpanel with a microfiber cloth and isopropyl alcohol or other electronics cleaner.

<!-- ## Troubleshooting -→

The hardware revision code is printed on the circuit board visible from the rear of the module.