IO Instruments Themisto

I couldn't find any other Eurorack VCO in this price range that offered so many features at the price. The obvious competitors are the Doepfer A110-1 and 110-2 but the Themisto wins out with its suboctave output, sine output and linear FM with attenuator.

I don't have proper test equipment, but as far as I can tell the tracking is very good over the audio range and the waveforms look precise - if you're looking for analogue "quirkiness" and "character" then you may have to add your own.

There are two jumpers on the back to enable v/oct and gate from the Eurorack bus.

Cons: The knobs feel a bit wobbly (even alongside low-cost modules from Doepfer and Behringer) and - although the fine tune knob makes it easy to tune accurately - the slightest touch on the coarse-tune knob knocks it off tune (I'm tempted to just remove the knob). That's why it doesn't get a clean 5 stars.

Documentation is minimal - you know how to use a VCO, right?

Being picky, an octave switch would have been a nice addition, and I'd prefer a layout with controls at the top and jacks at the bottom...