With the advent of digital technology in the early 80s, clever engineers were able to solve the tuning issue without completely redesigning the oscillators that provided the core sound of their synths.
This meant roadworthy polyphonic instruments could finally be produced for a price gigging musicians could afford, leading to the explosion of DCO-based synths I mentioned above.
DCOs vs. VCOs
Though DCOs proved an effective solution to the tuning stability problems of the late 70s, modern components can produce pure analog VCOs that hold their tuning well.
While they’re typically more expensive than DCOs or other oscillator designs, some vintage purists prefer synths with fully analog topology.
And though the sonic differences between the two are subtle, DCOs have their own vintage pedigree that lovers of 80s-style synth sounds will recognize.
But if you’re still confused, here’s a basic breakdown of the differences between VCOs and DCOs.
VCO:
Fully analog, including rate clocking
Found on older vintage synths and modern boutique analog synths
Older designs can suffer from pitch fluctuation and tuning issues
Costlier to implement effectively
DCO:
Analog signal, digital control
Found on synths from the 80s to today
Very good pitch stability
Can be produced cheaply, so often used for feature-rich polysynths and prosumer analog gear
How do DCOs work?
So if the signal generated by the DCO is still analog, where does the digital part come in?
Analog oscillators can be a bit hard to understand if you don’t have a background in electronics.
But the basic mechanism is that a capacitor gets charged up, discharged and charged up again in a predictable pattern.
The changes in voltage over time create a periodic wave that we hear as an audio signal when it gets amplified by a VCA.
In this model, a slow increase in the capacitor’s charge creates a rising initial phase of the waveform, followed by an abrupt drop when the voltage is reset before rising again.
This creates a waveform sometimes called a ‘ramp’ but more commonly known as a sawtooth wave.
The oscillator tuning problem arises from the analog circuit that tells the capacitor when to discharge and restart the ramp.
Even minor inconsistencies in the timing of the discharge can lead to fluctuations in the frequency of the oscillator’s output signal.
DCOs work by digitizing the reset pulse used to trigger the capacitor to discharge inside the oscillator circuit.
The result is a fully analog audio signal that’s kept in tune by the unwavering digital control pulse.
How to get authentic DCO-style sound in your DAW
With so many vintage instruments that depend on DCOs, you might be wondering what it takes to get their authentic sound in your DAW.
Luckily, emulating DCOs in software can be very convincing if you choose the right plugin.
We built our BA-1 synth to give you the best of the 80s in synthesis, right at your fingertips.
From accurate vintage-modeled oscillators to a juicy resonant filter, BA-1 is a simple yet powerful synth plugin with plenty of retro character.
Watch Alex break down the key features of BA-1 and demonstrate its capability for 80s-style synth magic:
