[sdiy] Wikipedia DCO article

[Eric Brombaugh]

Tom Wiltshire wrote:
> 
> On 14 Jan 2009, at 09:52, cheater cheater wrote:
> 
>> Note that most DACs nowadays are DSD followed by an integrator.
>> This means most NCO's turn out to be stream synths which means they
>> are just a whole lot of logic followed by a  classical DCO,
>> technically speaking.
>> I'm saying this because I class stream synths as DCO's. Is this right?
>> Cheers
>> Damian
> 
> I thought I was reasonably well informed on the topic, but I'm afraid I 
> have no idea what you're talking about.
> 
> What's DSD? What's a "stream synth"?

:)

DSD = Direct Stream Digital. This is a marketing term for delta sigma 
conversion architectures and is typically used to describe the data 
format used in audio systems like the somewhat marginalized SACD audio 
discs. If you do a web search on this term you'll find that a fairly 
large number of semiconductor manufacturers (eg TI, etc) are selling 
parts that generate/accept data in this format.

DSD data is basically a 1-bit digital data stream, taken directly from 
the two-level slicer of a sigma-delta ADC. Usually the data rate is 
~2.8MHz. In order to convert this format to conventional PCM (like a 
.WAV file) you have to integrate it and downsample.

That said, there's really no relationship between NCOs and DSD.

"Stream Synth" is something I can't help with. From context I'd gather 
that this may be another way to describe a fully digital synthesis 
system, but I've never heard it before.

Eric