Prophet-5 structure and the Virus matrix

    There are plenty of controller sources for the matrix modulation, some rather exotic ones like Data Entry, Random, or the KeyAna Course and Fine, which is great, yet some of those are probably not that often used.


    I was wondering if there is a technical reason why something like VCO 1 and 2 frequency are no legitimate modulation sources. On a modular system VCOs would obviously be the most used mod sources besides envelopes and LFOs.
    An LFO is not really helpful when you want to use a frequency higher than 100Hz and making the frequency change depending on Key Follow. So it would be good to know is there a technical hurdle which can not be overcome ?


    Especially since the structure of the signal flow and the whole layout of potentiometers and of course the filter "sound" are so ideal for making Prophet-5 type sounds, i would say no other VA would be as perfect for recreating classic P5 patches !
    For that and especially to recreate the Prophet Polymod, the only things missing are Oscillators as mod sources and Filter FM as destination.


    By the way, having Filt Cutoff 1+2 as a combined destination, very much like Osc Pitch 1+2 and Osc Pulse 1+2 on the LFO page would be helpful.


    Thanks.

    Zitat von prophonic

    I was wondering if there is a technical reason why something like VCO 1 and 2 frequency are no legitimate modulation sources. On a modular system VCOs would obviously be the most used mod sources besides envelopes and LFOs.

    The technical reason is very simple: CPU power. On most digital synths, modulation is updated at a much slower rate than audio (the LFOs on Virus go up to ~30 Hz if I'm not mistaken, so this should give you a ballpark figure). So, making audio-rate modulation possible would take two orders of magnitude more CPU power (and probably major redesign of the synth engine as well). Besides, you'd probably have to oversample (process everything at a higher rate than output audio), or the result will be full of nasty digital artifacts (aliasing) and basically unusable. The only hardware digital synth that I know of that allows full audio-rate modulation is John Bowen Solaris, and it's internal processing is done at 96 kHz.



    On another note, there's nothing exotic about Data Entry, it's just MIDI controller #6 - I use it all the time (assigned to expression pedal).

    Thanks for your reply. It makes sense, but then again the Virus has frequency modulation, at least for one Osc. So don't you think it should be possible to have that Osc appear under modulation sources as well ?


    Also, it's a bit hard to acknowledge that 10 year old software plugs like Pro-Five/52/53 or the Arturia plug can do something that the Virus can not. I am sure they are aliasing in higher registers, but i would rather have that than nothing.


    To complete your list of digital hardware synths, the Sonic Core Pro-12 has filter fm as well.

    Zitat von prophonic

    Thanks for your reply. It makes sense, but then again the Virus has frequency modulation, at least for one Osc. So don't you think it should be possible to have that Osc appear under modulation sources as well ?

    Apparently, oscillator FM is implemented differently, that is, not via the modulation bus. And in any case, it has tons of aliasing ;)

    Zitat von prophonic

    Also, it's a bit hard to acknowledge that 10 year old software plugs like Pro-Five/52/53 or the Arturia plug can do something that the Virus can not. I am sure they are aliasing in higher registers, but i would rather have that than nothing.

    Well I suppose the folks at Arturia were modelling a specific instrument and thus focused their development efforts on that.

    Zitat von prophonic

    To complete your list of digital hardware synths, the Sonic Core Pro-12 has filter fm as well.

    Even the 500$ Blofeld has filter FM, but still, it doesn't have oscillator as a freely assignable modulation source.
    Besides, modulation rate on the Blofeld is indeed much higher than on Virus (e.g. the LFOs go to kHz range, vs ~30 Hz on the Virus).

    ...and so we have come full circle.


    To summarize, filter fm is technically possible in digital synths with limited dsp resources and a limited clock rate, it has been done in hard and software for around 10 years with processing power of that time.
    Since FM has been implemented in the Virus at least for one Oscillator, i have faith in Christoph's and Marc's programming skills that they would be able to find a way to implement that for Filter FM as well.


    Aliasing in FM ? Bring it, the DX7 sounds great for its quirks as much as for its features. I mean, FM in the prophet doesn't sound exactly crystal clear either.