[sdiy] BBD's in series and accumulative S/N ratio degradation.

[Magnus Danielson]

On 12/23/2011 02:30 PM, Mattias Rickardsson wrote:
> On 23 December 2011 13:36, Tom Wiltshire<tom at electricdruid.net>  wrote:
>> you're supposed to filter the signal between stages to remove clock noise. The clock noise will (in theory) cause aliasing in the next BBD
>
> Oh, is that so even if you use the same clock?

The same clock doesn't really help, as this is thermal and 1/f noise on 
the voltage levels. However, any filtering hardware will remove higher 
frequency noise and add some noise itself. You can remove mirror images, 
and in that context the same clock is relevant, but very small variation 
in clock frequency would not be significant disaster.

The pass frequency of the filtered signal (where we have our audio) 
would get no filtering effect of the noise added there, but additional 
noise from the filtering components would be seen, even if this could be 
kept low.

If you want to combat noise, then reducing the dynamic range is one 
method, running BBDs in parallel would also be possible.

> I wonder if this somehow could be cured easier when the clocks are
> known to be the same. Massive filtering might be a bit "over the top".
> :-)

Indeed.

Cheers,
Magnus