Filter Saturation For One Oscillator Only?

  • Hi all,
    There is a little trick you can do on the Blofeld using the sine shaper in one filter drive section to do some simple phase modulating with two oscillators. (I'll explain further on request.) Even though the TI2 has a Phase Modulation option in Osc 2, I was trying to do this PM trick using the wave shaper in its saturation section but couldn't pull it off correctly because apparently saturation always effects all oscillators and you need to have it affect only one osc while also using another osc without saturation. I tried different combinations of osc balance, filter balance and series/parallel modes, but no luck.
    So, is it possible to have filter saturation for one oscillator only??
    Thanks!

  • Thanks Poly! Yes, I tried Split Mode but it still seemed like all oscillators are still affected by Saturation. I'll try your suggestion again, though. :)

  • Hi all,
    There is a little trick you can do on the Blofeld using the sine shaper in one filter drive section to do some simple phase modulating with two oscillators. (I'll explain further on request.)


    As mentioned by Poly, the split filter mode does what you want.


    Care to tell a little more how wave shaper and phase modulation are related?

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  • As mentioned by Poly, the split filter mode does what you want.

    Still no luck in the context of my intended usage! (see below)

    Care to tell a little more how wave shaper and phase modulation are related?

    Absolutely! The wave shaper uses a sine wave to morph whatever wave you send to it. (You probably already know that!) Technically, this is not Phase Modulation but you can get some nice timbres out of it. I'm so glad Access included this feature on the TI2 and especially the PM function in Osc 2 Wavetable mode! (BTW, the wave shaper in the Distortion effects is, of course, for distortion and not usable for this purpose.)
    The Blofeld PM trick I learned from a member of Till Kopper's Waldorf forum. I use to not be much of a fan of the DX7 until I heard Wendy Carlos' later PM albums and love how she uses it for Baroque tones.
    On the Blofeld, for a 2 Operator PM algorithm:
    1. Send a saw to a filter with the Drive Curve set to Sine Shaper.
    2. Set the saw Osc level to 111 and the Filter Drive Curve level to 35 and you will hear the saw turn into a sine. That will be the Carrier.
    3. For the Modulator, send any wave you like (a sine if you want classic DX basic tones) from another Osc to the same filter and as you fade that Osc in you will hear it phase modulating the Carrier. Turn on Osc Sync so the phasing cycle always starts at the beginning per key strike (of course).
    4. For a 3 Operator Parallel algorithm fade in the remaining Osc (another modulator) to the same filter.


    As far as needing a saw for the sine shaper to turn it into a sine for the carrier, it works while other waves won't. That's all of the technical aspect of it that I know! But its a lot of fun to experiment with, especially using various other waves for the modulators. :)

  • 3. For the Modulator, send any wave you like (a sine if you want classic DX basic tones) from another Osc to the same filter


    But then you're sending both OSC1 & 2 into the same filter? Which means you don't need to split. Also, I don't get how carrier and modulator then are any different. ?(

    Bass Player and Synthesist.
    Virus TI2 Darkstar | Virus TI2 Desktop | Sub 37 | Voyager RME | Machinedrum | Analog Four | Digitone | MPC Live | NI Maschine+
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  • Sorry for all the editing of my post, but once again Oli, you got me thinking!

    But then you're sending both OSC1 & 2 into the same filter? Which means you don't need to split.

    Correct. After further investigating on the TI2, I am getting the results that should be expected with this setup:
    1. Filter Mode: Series 4, Balance: --64
    2. Set Filter Saturation to Wave Shaper, level 0
    3. Set Osc 1 to a saw, osc balance: -100%. It will sound like a sine.
    4. Set Osc 2 to a sine (basic example), no detune.
    5. Fade in Osc 2 with Osc Balance up tp 0% to hear Osc 1 being phase modulated..
    6. Fade in Osc 3 with a sine (basic example), no detune, for another parallel modulator.


    This time I noticed no saturation with filter balance set to +63.

    Also, I don't get how carrier and modulator then are any different.

    The carrier level (Osc1) stays the same but the modulator levels (Osc 2 and 3) are variable.


    Thanks for chiming in on this thread, Oli. :)

  • The carrier level (Osc1) stays the same but the modulator levels (Osc 2 and 3) are variable.


    That's not entirely true: OSC 1 & 2 are level balanced, so the "carrier" OSC 1 does not stay the same as OSC 2 is faded in. Thus, when OSC 2 is at 50% you are actually sending an equal blend of 50% saw (OSC1) and 50% sine (OSC2) into the wave shaper. That's different from having 100% saw and adding a sine.


    I think that's probably one of the main differences you have with this approach compared to the Blofeld.


    Also, I don't think that the result of sending a sum of two oscillators into a wave shaper is the same as OSC 1 phase modulating OSC 2 (or vice versa).



    Anyway, you lured me into experimenting with the wave shaper and with the Wavetable Phase Modulation, which resulted in some quite unexpected spectra. Thanks for that :)

    Bass Player and Synthesist.
    Virus TI2 Darkstar | Virus TI2 Desktop | Sub 37 | Voyager RME | Machinedrum | Analog Four | Digitone | MPC Live | NI Maschine+
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  • That's not entirely true: OSC 1 & 2 are level balanced, so the "carrier" OSC 1 does not stay the same as OSC 2 is faded in.

    Yes, I just discovered this myself when I was checking Osc Balance function with one osc muted using the pulse 100% width trick.

    Thus, when OSC 2 is at 50%

    You probably mean when the Osc Balance control is straight up (which reads +0%) ?

    That's different from having 100% saw and adding a sine.

    And also throws the saturation level "balance" off a little too, I noticed.

    I think that's probably one of the main differences you have with this approach compared to the Blofeld.

    Yes, the fact that Blofeld offers all osc levels individually. And I noticed on the TI2 you get a wider modulation range with osc 3's separate volume control than on Osc Balance.

    Also, I don't think that the result of sending a sum of two oscillators into a wave shaper is the same as OSC 1 phase modulating OSC 2 (or vice versa).

    Actually it is as long as the wave shaper is converting one osc's saw into a sine for the carrier, according to some lengthy emails I got into with the expert who introduced me to all of this on the Waldorf Forum, with some technical info that was over my head. I think the real caveat is the fact that the modulating sine also gets morphed by the waveshaper as it's affecting the carrier instead of remaining a pure sine (the reason for my first post). Also, there is the question of if the algorithm is to be additive or not, i.e., hearing all the oscs working at the same time or, only the carrier as it is affected by the modulators.

    Anyway, you lured me into experimenting with the wave shaper and with the Wavetable Phase Modulation, which resulted in some quite unexpected spectra. Thanks for that

    You are very welcome, Oli! This also helped clear up some misconceptions for me. And its really great that at any rate we now have some more interesting waveforms at our disposal! :)

  • After playing with this some more (still not getting the results I am after, btw) I noticed myself that Saturation applies in whichever routing only to Filter 1 if I'm not mistaken (hence the Spilt Mode suggestions?), something that I could not find specifically stated in the manual. This bit of info might be of help in other applications also. :)