The ACL Variable Sync VCO consists of one ramp core oscillator with several wave shaper sub-circuits, all having that classical vintage tone, loved by a lot of musicians and sound synthesists. The VCO is capable of delivering that without sacrificing tracking precision and low temperature drift.

Available waveshapes are saw, inverted saw, triangle, sine and PW rectangle, which uses the saw wave from the waveshaper as a carrier for the PWM. It can be varied by CV and manually within a range from 0 percent to almost 100 percent.

The possibility to play VCO in low, middle and high modes, together with the 10 turn precision Tune pot results in a very convenient ”on the fly” way of tuning the module. It's core can be frequency modulated exponentially from two inputs, both CV controlled. When fully open the input attenuators are calibrated for 1 V/Oct. There is one more input - for linear modulation with manual amount control, AC coupled and configured like differentiator. In this way it is sure no detuning caused by DC, will take place when modulation signal is presented at the FM Input, but only frequency modulation, centered around the already played tone. Syncing the core to outside source makes a whole lot of difference, when there is the additional option to vary continuously by CV and manually the threshold of synchronization from no sync, soft sync and hard sync.

This input is configured as attenuverter for even more flexibility. Note when the Threshold pot is fully CW there will be no sound output anymore. The reference wave source for the soft sync is the saw from the oscillator. Sync input itself reacts to every repeatable waveform with amplitude higher than 1,2 Vpp.