Can the digitone do though zero fm?
it does phase modulation, which is better 
. Similar result and more stable
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with the lfo wich are fast enought you can experiment analogish modulation on tthe filter and amp also
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Phase mod is nice. Still have my first synth here a cz101. But I have to look up the differences.
And yeah the lfo audio rate mod is also a great feature.
Since some eurorack modules do TZFM and the Digitone is very special in FM Sound generation i would have expected that it can also do tzfm.
The terminology is quite confusing.
Most popular “FM” synths derived from similar architecture to the Yamaha DX series use phase modulation, where the modulators are modulating the phase of the carrier operators, not the frequency. This is largely down to the fact that phase modulation tends to be more stable, musical and predictable than straight up frequency modulation, especially when dealing with multiple operators arranged algorithmically.
A lot of Eurorack FM tends more towards analogue (or analogue style) oscillators modulating each others’ frequencies. Thru zero FM simply solves the issue of things going absolutely batshit when modulated signals go past zero by reversing the phase of the carrier waveform as it goes past zero, making it more stable, musical and predictable.
So Phase Modulation style FM synths don’t really need thru zero capabilities, as the problem that thru zero is attempting to solve isn’t really apparent on Phase Modulation synths in the same way it is on more analogue or modular systems.
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The cz series is phase distortion, most “FM” synths are phase modulation (related but not identical). Analog oscillators implement TZFM because it improves tuning stability under deep modulation. It’s unnecessary in a digital phase modulation implementation
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Phase Modulation animation at 6’30’’.
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Through zero fm, all things are possible.
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Through zero FM is a term used in analog oscillators to mean that it can do frequency modulation while maintaining the percieved pitch of the oscillator by reversing the waveform direction (going “through” 0hz frequency into “negative” frequencies). It is basically taking the concepts of digital FM synthesis and trying to make analog oscillators do roughly the same thing. So yeah, you could say that the digitone (and all digital FM synths) do through zero FM, otherwise the pitch would not stay stable at high modulation depths.
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Short answer, no.
It doesn’t do FM. It does VPM. So it doesn’t need through zero frequency modulation.
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What is VPM? Never heard if it.
Or do you refer to VPS?
Variable phase modulation.
As mentioned above.
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Frequency Modulation (FM) in its most basic form is any signal modulating the frequency of an oscillator. On older analog equipment this input was often exponential which is good for keyboard/pitch input but has issues like shifting the fundamental pitch when you increase the index. Linear FM on the other hand modulates relative to the fundamental pitch symmetrically which sounds a lot more musical.
Thru-Zero is a separate concept where the oscillator (or phase accumulator) can handle negative phase/voltage, meaning basically that it can go backwards. This is especially nice when you’re using Linear FM because once you pass through zero hz the oscillator reverses which results in even sidebands on the negative side of the signal.
Yamaha’s implementation of Linear FM in a digital system was done using Phase Modulation which modulates the phase of the oscillator instead of the frequency. This is 1) less computationally expensive and 2) more stable and less problematic wrt to maintaining the fundamental frequency of the oscillator. We can also introduce things like feedback in a PM system without pitch issues. Genius-level engineering from team Yamaha at the time.
Yamaha patented this FM implementation which meant that other manufacturers had to come up with their own alternative approaches.
Casio came up with Phase Distortion which is very closely related to PM but instead changes the shape of the phase signal itself instead of just adding a signal to it. This results in the oscillator (usually a lookup table) bending, contracting etc as a result of the non-linear phase.
Korg came up with VPM which is very similar to Yamaha’s FM but … Different branding? Not sure.
Now where does Thru-Zero fit into all of this? Well the PM/PD/VPM/LINFM/EXPFM oscillator itself could still support negative phase, and this could of course be interesting regardless of the inherent method used to generate the base sound.
In a system like Digitone this is perhaps not so interesting because you already have the kind of timbres at hand that you’d get from Linear TZFM with the benefits of PM. But it’s not incorrect that being able to modulate the resulting sound (carrier) with Linear TZFM could yield interesting results.
But regardless if the Digitone’s phase accumulators can handle negative (I don’t know) there’s not really a modulation source that could make full use of that. Plus, the aliasing would likely be problematic.
So in short, the Digitone doesn’t really benefit from having TZFM.
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look at this guy, like he designed the damn thing
[ducks]
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