[sdiy] High frequency VCO as BBD clock

[brianw]

It seems like there are two challenges here, each with potentially a different solution.

A) Current drive. Whatever you use to generate the BBD clock, you should be able to handle the current drive with a buffer. There are certainly op-amp buffers with radio frequency bandwidth that could link your clock to the BBD inputs with sufficient drive. It should not matter how you generate the clock, so long as the high-current buffer is clean.

B) Frequency. I've been thinking about the same issue. Other replies have suggested that the CA3080 can directly handle the frequencies required. I've been wondering whether a PLL or DPLL could be used with an audio frequency VCO to boost the frequency into the higher sample rate clock needed. My goal is to have a CV input to the VCO for flexible frequency control. As long as the (D)PLL tracks with reasonable response time, it seems possible to link things up in series.

e.g. CV -> VCO -> PLL -> buffer/driver -> BBD

Brian Willoughby


On Feb 7, 2023, at 10:18 AM, Rutger Vlek wrote:
> For a while I've been working on a guitar pedal board for personal use. I'm about to build the second revision of a solid state pre-amp, and was thinking about possible modulation effects too. I would love a nice (stereo) BBD flanger/chorus, but felt a bit fed-up with all the 'classic' designs, particularly the traditional clocking scheme, usually with a limited range, lack of current drive (to overcome capacitance of the BBD clock input) and strictly linear modulation (calling for a hyper-triangle modulation source).
> 
> Having some experience with designing saw- and tri-core VCO's around the 2164, I was wondering how easy it would be to push the design of a typical tri-core VCO with an 2164-based expo converter into higher frequencies (let's say up to 500kHz) and use it to clock a BBD? Has anyone tried? Or are there fundamental reasons why such frequencies are not possible? I've never (intentionally) worked with circuits outside of the audio bandwidth...