[sdiy] Re: Inexpensive 16 bit DAC?

[Antti Huovilainen]

On Sun, 24 Apr 2005, Bob Weigel wrote:

> In boards where effect calculations are done, we know it's good to keep 
> 24bits going in the digital real to keep enough headroom not to loose quality 
> at points.  Once things are being converted back to the analog realm 16bits 
> starts to sound quite adequate.   12 bits with 4 bit exponent 
> however...sounds better.  I use a Kurzweil K1200 and one of the things I love

Properly designed systems use dithering to fix this. Quantization noise 
sounds quite horrible because it is correlated to the wanted signal 
(indeed, quantization distortion is a much better term). By adding some 
(+- 0.5 LSB) random noise before quantization, the error is not correlated 
to the signal anymore and the distortion is eliminated.

With dithering, the bitdepth of the DA converter only determines the noise 
floor of the signal. The situation can be improved even more by shaping 
the noise power to be mostly in areas where ear is less sensitive. This 
way some additional 10 dB perceptual SNR improvement can be had.

You can try the results if you have a program that can use variable 
dithering and quantization levels. Using foobar2000 (mp3 player), I found 
that 8 bits is quite acceptable with modern overcompressed pop music and 
for some cases even 6 bits would be enough!

Antti

"No boom today. Boom tomorrow. There's always a boom tomorrow"
   -- Lt. Cmdr. Ivanova