[sdiy] High frequency VCO as BBD clock

[Pete Hartman]

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 <pete.hartman at gmail.com> 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.
>
> Pete
>
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