[linux-audio-user] Linux music editor, less than 16-bit ?

Florin Andrei florin at andrei.myip.org
Mon Feb 26 13:42:13 EST 2007


Frank Barknecht wrote:
> 
> Hey, that's actually the first time I read about 1-bit recording and
> at first I thought you were joking or had a typo. But you weren't and
> hadn't.

It works pretty well and is easy to implement in silicon.

Back in college, using a few square inches of printed circuit board, a 
soldering iron and a handful of components, I made two little devices 
whose only purpose in life was to:
1. Grab an analog input and transform it into a 1-bit digital signal
2. Grab the 1-bit digital signal and convert it back to analog

Not very useful in practice, but a fun project for a boring week-end 
afternoon. The toys were so simple, they didn't even have a clock, the 
transitions between 1 and 0 happened whenever the proper conditions were 
met (there was a capacitor somewhere that was either charging or 
discharging very quickly, with the average voltage trying to follow the 
analog input, and it was sending to the digital output the information 
of either "I'm charging" or "I'm discharging"). I guess the digital 
"carrier" was somewhat self-stabilizing (somewhere in the MHz range I 
guess).
Those of you familiar with electronics can probably figure out the rough 
design of the scheme already.

The sound quality was pretty damn good too, which is somewhat odd given 
the rudimentary technology.

With minimal effort, more complex converters can be made that can offer 
much better quality. Mine was a hack.

>   Single-stage, 1-bit sigma-delta converters are in principle
>   imperfectible. We prove this fact. The reason, simply stated, is that,
>   when properly dithered, they are in constant overload. Prevention of
>   overload allows only partial dithering to be performed. The
>   consequence is that distortion, limit cycles, instability, and noise
>   modulation can never be totally avoided.

Interesting.

-- 
Florin Andrei

http://florin.myip.org/



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