ThreeFingersOfLove wrote:John,
I would like to ask:
1. How many modulations sources can modulate a filter? are their depths/offsets adjustable?
2. How many modulation sources can modulate an oscillator? are their depths/offsets adjustable?
All oscillators and filters have 4 independent modulation paths each. For each path you have the following structure:
Source - Amount - Control - Strength - Destination
The Mod Source list is quite extensive; it includes all audio sources and all control sources. The Amount is an initial amount; the Control and Strength act as a sidechain control of the initial amount. The list of Control Mod Sources for sidechain control do not include audio rate sources. Both the initial Amount and Strength parameters are bipolar.
The possible destinations depend on the section the mod paths are in - for oscillators, you have exponential and linear frequency mod, or shape mod. For the filters, you have cutoff & resonance for all, plus damping for the Comb Filter, and crossfade and frequency for the Vocal Filter.
3. Is there provision for HEADROOM either to accomodate resonance build-ups or modulation of levels? If not is there some gain compensation circuit for resonance?
The Multimode Filter has gain compensation, the SSM and Mini do not (probably also not in the Obie, but I don't recall right now). You also can control the post-filter signal level at the VCA Output level.
4. Is it possible to route the output of the FX section back to the mixer? By looking at the signal flow, maybe it's possible to do physical modeling:
a. Short burst of white noise (either shaped from a AD) or directly from a small sample in order to provide the initial excitation -->
b. Input mixer that provides a z-1 function for feedback IF there's provision to route the signal back. The z-1 function can be a crude 6-pole lowpass filter which is used in a lot of Karplus strong models -->
c. Delay lines: there is a delay FX but I wonder if it can be stacked, i.e. used multiple times (maybe even at the expense of other effects) so as to provide the tuning.
This is what the Comb Filter's Tube model is for. The Comb Filter is a delay line, and uses the onboard RAM. There is a lower limit to the frequency, based on the maximum amount of RAM allocated (I don't have the proto right now to check, but I can report what that frequency is later).
The Damping control is a 6 dB lowpass filter built into the feedback circuit of the Comb Filter. If you want to add additional filtering, at this point you will have to use 2 filters in series. The Main Effects are outside of the synth engine, and so are not integrated on a per-voice basis, as are the Comb Filters. The Main FX are not stackable, but in an 'FX Pool'. Once you use one of them in an FX Bus, it is no longer available to the other busses.
-John B.