[sdiy] High frequency VCO as BBD clock

[brianw]

Thanks for the correction.

I was just about to ask how terrible the bandwidth would be when a BBD is clocked at 2 kHz down to 200 Hz. I'm sure it would make a useful effect in some situations, but more of a low-pass filter than anything else. ;-)

Brian


On Feb 7, 2023, at 12:27 PM, Pete Hartman wrote:
> Correction to myself
> 
> It's 200KHZ to 2.0 KHZ.  Shouldn't read in a hurry :)
> 
> Pete
> 
> On Tue, Feb 7, 2023 at 2:12 PM Pete Hartman wrote:
>> John Blacet's Time Machine uses a VCO in some ways similar to this.  He has a VCO constructed with an LM13700 and a single op amp from an LM324, and then uses a transistor buffer into a CD4013 to make the two-phase clock that the BBD uses (an MN3005).
>> 
>> For the MN3005 the clock out from the 4013 only has to go from 2KHz (shortest delay) to 200Hz, so you don't get up into the tens or hundreds of kilohertz for that.  In John's case he also put clock driven aliasing filters around the BBD (LTC1063), and those need 80KHz - 800KHz -- those are generated with a 4046 and a 4518 to make a clock multiplier from the VCO range, so the filters adjust their cutoffs to accommodate the different BBD rates.
>