[sdiy] Digital audio demo on Youtube

[ASSI]

On Tuesday 18 February 2014, 11:33:36, cs80 at therogoffs.com wrote:
> I’ve read about the affects of ZOH using standard sample/hold DAC outputs
> but what’s the alternative?  In mathematical theory, the DAC output
> should be zero-width pulses whose area equal the sample value.

The alternative to an S&H would obviously be a signal source that 
approximates a delta pulse (in the distributive sense) better than a 
rectangle of fixed width (the sample period).  But if that width is kept 
small, the approximation is already quite good, so there is not much to 
gain.

> Do you have pointers to articles / part specs on DACs that try
> and approach this?

Looked at from some angle, this is what some UWB transceivers are trying to 
do.  Also some extremely high-speed DAC designs where the linearity of an 
S&H falls to pieces or requires too much power to maintain have experimented 
with shaped pulses (search for return-to-zero DAC and then take it from 
there).

But for reasonably slow signals, an S&H is obviously too convenient to pass, 
just oversample sufficiently to ease the reconstruction filter design, 
reverse the sinc distortion the rectangle pulse produces and pretend these 
had been delta pulses all along.  These days audio is as slow as glacier 
from the perspective of a modern semiconductor technology and an audio 
DAC is largely viewed as a solved problem, so I guess nobody bothers to 
explore really different concepts except perhaps in academia.  Things are 
becoming different for implantable or autonomous sensor and actor elements 
since they generally need to operate at much lower power levels and may have 
to make do with much slower technologies like organic TFT.


Regards,
Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

SD adaptations for Waldorf Q V3.00R3 and Q+ V3.54R2:
http://Synth.Stromeko.net/Downloads.html#WaldorfSDada