Doepfer - A-188-9 Highspeed VCO

The Doepfer A-188-9 is like the warp drive of VCOs, propelling frequencies up to 500kHz, way beyond your typical audio range. It tracks pitch smoothly at 1V per octave and is designed to stay on point across a huge range. One of the main applications for this module is to work in conjunction with BDD modules to generate exact delay times for Karplus-Strong synthesis. That’s the string-like sounds you can forge out of really short delays. This module pairs especially well with some of Doepfer’s own BBDs, like the A-188-1 and A-188-2.

The usual suspects of VCO waveforms are all present—sawtooth, triangle, and rectangle with adjustable pulse width. There’s a frequency divider that can can lower the frequency into the Audible range, which turns it into more of a standard VCO. When you flip it into high-speed mode, it’s ready to work with other gear that needs those fast signals — such as video synthesis modules. That means that the A-188-9 is like having two VCOs in one: normal audio and turbocharged high-speed one that can work in the sample-rate domain.

The built-in phase-locked loop (PLL) is sort of like the module’s control system. It ensure that the high-speed VCO stays synchronized with the audio VCO. It does so by comparing the frequency of the audio VCO to a reference signal, then adjusting itself to match, essentially locking onto the pitch and tracking it. The PLL can multiply the frequency of the audio VCO by 32, allowing the high-speed VCO to reach those extreme frequencies (up to 500kHz). The slew limiter lets you control how fast the PLL responds to changes, which is useful for minimizing unwanted artifacts like a ripple in the signal. In order to better understand the whole concept of how PLL works you can check out the Doepfer A-196 PLL.

You might already have a collection of classic VCO’s that work within the audible range, what you might not have is one that enables you to explore whatever lies beyond that. As stated above, this module is great together with BBDs for anyone interested in karplus-strong synthesis for people who need VCO’s that can generate frequencies in the sample-rate domain.

Features:

• Dual mode: Audio VCO and High-Speed VCO (up to 500kHz)
• Works well with BBD modules (Karplus-Strong synthesis)
• Standard audio VCO waveforms: sawtooth, triangle, rectangle
• Pulse width modulation
• Phase Locked Loop (PLL) with slew control
• Adjustable slew time for control of artifacts (ripples)