[sdiy] Frequency shifted from BBD?

[Didier Leplae]

> My Flangelicious design uses a uP to generate an LFO-modulated BBD clock. The LFO is done in firmware and the clock is an NCO hardware module on the microcontroller. It makes for a very simple circuit compared to most flangers, but it has a weird watery R2D2-like background noise caused by (I think) frequency spurs from the NCO. A genuine VCO for the BBD would sweep smoothly and eliminate this source of noise.

Do you think this is specifically a problem with the PIC’s hardware NCO or do you think this is inherent to any digital clock?
There seem to be a bunch of BBD based devices that have tap tempo for example, which I imagine must be done with a uP.

In fact I make already make a delay module like this, but it seems to present more of a problem with chorus and flanger circuits because of the higher frequencies.