[sdiy] High frequency VCO as BBD clock

[René Schmitz]

Am 07.02.2023 um 19:18 schrieb Rutger Vlek via Synth-diy:
> Dear list,
>
> 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...
>
On the 2164 there is typically a 500 ohm + 560p  RC at the input that 
delimits the bandwidth. That chip has a mere 500kHz to begin with. One 
would have to see if the chip is fast enough to be accurate at that speed.

There is a VCO circuit with a CA3080 in the datasheet that is claimed to 
be working up to 1Mhz.


Best,

  René