[sdiy] Suitable DACs for Demultiplexing

[cheater cheater]

The output will never settle

On Thu, Oct 22, 2009 at 1:47 PM, Ingo Debus <igg.debus at t-online.de> wrote:
>
> Am 21.10.2009 um 22:17 schrieb Tom Wiltshire:
>
>> However, I ran into a problem. The DAC is a Sigma-Delta type and uses an
>> upsampling digital filter to produce a pulse train at 256 times the sample
>> frequency. What this seems to mean is that the output is filtered. Instead
>> of stepping abruptly from one sample to another, it glides smoothly between
>> them. Obviously for audio (the DAC's intended purpose) this is ideal
>> behaviour, but for demultiplexing it's a nightmare. The output sample has
>> only just reached the level you wanted it to have when it is time for the
>> next one to be sent. The effect on the demultiplexed outputs is for an
>> 'echo' of the previous channel's signal to break through on each output
>> channel.
>
> Could still work if you add a delay after outputting tha DAC value and
> before enabling the multiplexer. This delay has to be long enough for the
> DAC output to settle.
> This requires a multiplexer that can be disabled of course, like the 4051
> for instance.
>
> Ingo
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>