Three Thru Zero

Comparing the thru-zero linear FM response of the Cyclonix Cyclebox to the Cyndustries Zeroscillator and Harvestman Hertz Donut.



I like timbral oscillators and use them in my live sets. The Zeroscillator is too big to gig with, so the Hertz Donut usually takes its place. While it packs a lot of features into a small space, the HD is less than hi-fi, so I was hoping the better-spec'd Cyclebox might be an alternative.

In this comparison, I've focussed on thru-zero linear FM as that is what I'm interested in. For demos of the Cyclebox's other features, look here.


dynamic, sine-on-sine. (0:00) zo, (0:09) cb (lead out)


ibid. (0:00) zo, (0:25) cb, (0:45) hd

Despite a firmware upgrade, the Hertz Donut tends to break up in the upper registers. Here's how the three cope with higher pitches:


(0:00) hd, (0:06) cb, (0:13) zo. (0:21) zo, (0:28) cb, (0:36) hd

I matched the pitches of the principal and modulating oscillators by ear, using mode 0010 on the CB for examples 2 & 3. On the ZO & HD I increased the modulation depth as far as I could before pitching artifacts were evident. The CB's FM index was set to full.

As you can hear, the CB doesn't seem to allow the same level of modulation as the ZO & HD, so it sounds muted by comparison. This can be addressed to an extent by increasing the gain, but as this feeds the wave-folder, the results are not the same. It's not clear from the manual whether the internal ratio setting is discrete or in semi-tones, but this might explain why it's easier to achieve clangorous/ bell tones on the ZO & HD. Overall, the CB's linear FM response reminded me of the Livewire AFG, namely better than most non-thru-zero VCOs, but lacking in brilliance.

The Cyclebox is more hi-fi than the Hertz Donut, but because I couldn't push the index as far in a dynamic FM patch, I found it lackluster. Both digital VCOs offer a built-in modulator, smaller footprint and more stable FM. However, despite the inaccuracies of analogue, I prefer the thru-zero linear FM tones of the Zeroscillator.