Somewhere in the manual, it does describe D-Mod & S-Mod as AM & FM, which may be obtuse, but it is perfectly descriptive of what is actually going on with the dual modulations.
The majority of the ModFactor controls are all interactive. You didn’t mention D-Mod position in your description. That’s crucial to the secondary LFO (bottom row) parameters. It will modulate the primary Depth setting, and it is also tied to the Mod Rate.
I think it’s easier to hear the relationship between the two LFOs in Tempo Mode, at some standard BPM. Set up a test patch in TremoloPan (as that algo is all about depth of amplitude). Use matching sharp-edged LFO waveforms:
- Intensity / Edge – 99
- Type – Opto
- Depth – 99
- Speed – 1/4 … 1/16 ***
- Shape – Square
- Width – 0 (important to this test)
- D-Mod – 0
- S-Mod – 0
- Mod Rate – 8.000 x Speed … 0.125 x Speed ***
- Mod Source – Square
*** If you set up opposing Speed & Mod Rates (say 1/16 Speed with 0.125 x Speed as a Mod Rate for starters), it’s easier to hear what each LFO is doing.
All primary LFO (top row) tremolo; no secondary LFO (bottom row) influence. Then …
- Dial up D-Mod, leaving S-Mod at 0.
- Adjust the Mod Rate multiplier.
- Dial up S-Mod, returning D-Mod to 0.
- Adjust the Mod Rate multiplier.
I’ll often start out with midpoint values in the secondary controls, and tweak from there:
- D-Mod at 50
- S-Mod at 50
- Mod Rate at 1.000 x Speed
The advanced test uses SLOW / FAST switch to drop the base Speed down to 1/8 of it’s indicated speed. You may need to adjust the overall BPM with that toggle.
