Surge XT's Ensemble effect models BBD bucket-brigade delay lines for authentic analog chorus character

The Ensemble effect in Surge XT implements BBD (bucket-brigade device) chorus using a 2018 DAFx paper model by Holters and Parker. BBD chips pass samples through discrete analog stages at a clock rate, which creates the characteristic slightly gritty, warm chorus sound. Parameters include Anti-Alias Filter (input bandwidth), Modulation Freq 1/2 and Depth 1/2 (two independent chorus LFOs), Delay Type (128 to 4096 BBD stages or clean digital), Clock Rate (the BBD clock speed — lower rates produce more obvious artifacts), Saturation (BBD-style saturation on the delay lines), and Feedback (creates flanging when raised). The digital delay type option provides a cleaner, clinical chorus for comparison.

Examples

Set Clock Rate to 10 kHz, BBD 512 stages, Saturation at 30% for vintage string ensemble character. Compare to Digital delay type for the difference in warmth.

Assessment

How does Clock Rate in the BBD Ensemble differ from Modulation Rate? What sonic artifact does a low Clock Rate introduce that a digital delay would not?