A “DC signal” (Direct Current signal) refers to a constant voltage level or a voltage that does not change over time. Unlike AC (Alternating Current) signals, which oscillate or vary periodically, DC signals maintain a steady voltage level, such as 0V, +5V, or -5V.
DC signals can have various uses in a modular synthesizer system:
- Offset: DC signals can be used as an offset to change the baseline or reference voltage of a modulating signal. For example, you might add a DC signal to a bipolar LFO (oscillating between -5V and +5V) to shift its range to be unipolar (oscillating between 0V and +10V).
- Control: In some cases, DC signals can be used as control voltage (CV) inputs to set static parameter values in modules, such as the cutoff frequency of a filter or the pulse width of a square wave oscillator.
- Mixing: DC signals can be mixed with audio or other modulation signals to create new signals, either by summing or multiplying them using a mixer or a voltage-controlled amplifier (VCA), respectively.
- Manual control: Some modules can generate DC signals using knobs or sliders that allow users to manually set a voltage level, which can then be routed to control other parameters in the synthesizer system.
It is essential to note that while DC signals can be useful for controlling or modulating various aspects of a modular synthesizer, they are not suitable for audio processing or synthesis since they do not contain any frequency content or changing amplitude. In some cases, modules in a modular synthesizer system may have AC-coupled inputs, which block DC signals to prevent them from affecting audio or other AC signals.