[sdiy] BLIT/BLEP virtual analogue synthesis

[Eric Brombaugh]

On 08/04/2010 12:56 PM, Olivier Gillet wrote:
>
> Would it be a stupid idea to get away with the downsampling, put
> instead a sigma-delta loop and just output a bit at, say, 8 Mhz, so we
> could also get away with the DAC and just put a simple analog low-pass
> on this bitstream? Am I wrong to suspect that the very first thing a
> modern audio DAC would do with the signal you have carefully
> downsampled to 48 kHz, is to upsample it back to several MHz for
> sigma-delta conversion?

That would certainly work and would be very inexpensive. I don't believe 
that simple 1-bit DACs like that are capable of particularly 
high-quality audio though, so adjust your goals accordingly.

You're not wrong about DACs, although bear in mind that when they 
upsample, they're doing so with bandlimited interpolation which ensures 
that there is little to no signal energy outside the audio band. This 
makes the analog reconstruction filters after the DAC a lot easier to 
design.

Eric