[sdiy] BBD question

[Ingo Debus]

Am 30.08.2008 um 05:05 schrieb Nicholas Gregorich:

> Ian Smith wrote:
>> I've got the old Panasonic BBD manual and it shows one with a 20  
>> kHz 12dB lowpass filter at both the input and output... I'm  
>> guessing that's to reduce clock noise. So I'm thinking have a  
>> filter at the beginning of the chain and between each BBD and one  
>> at the end.
>
> The one at the input is probably considered an anti-aliasing  
> filter, and at the output a reconstruction filter (reduces clock  
> noise). In that case a filter between BBD stages is probably a good  
> idea to prevent aliasing in the second BBD.
>

I've got no experience cascading BBDs, but I can't see a reason why  
an anti-alias or reconstruction filter would be required between the  
BBDs as long as they are driven from the same clock.
It's a whole different story if different clocks are used. Then sure  
filters are required.

Ingo