On Mon, 2004-04-12 at 09:27, Steve Harris wrote: > On Mon, Apr 12, 2004 at 06:21:33AM -0500, Martin McCormick wrote: > > Now, here is something I am a bit unsure of, myself. I know, > > from actual observations that a straight PCM output from your basic > > A/D converter if read as unsigned numbers moves in steps from 0 to all > > 1's on. I honestly have not tried to interpret those data as signed > > numbers because it wasn't convenient at the time. If one wants to > > have a valid representation of what the wave form is doing for > > graphical or calculation purposes, then the mid-point would have to be > > what one would call 0 level with -1 being one below and 1 being 1 > > above, etc. I am certainly not arguing with anyone, but am a wee bit > > confused as to the correct way to represent the numbers. > > Audio AD converters are asymmetrical - abs(minimum_voltage) is higher than > maximum_voltage. Audio AD converters sometimes have unsigned modes, but > they seem to have different behaviour. I checked up recently to make sure > JACK was doing the right thing(TM) when converting between floats and > ints. This stuff is explained in detail in the AD converter spec sheets > for the AD converters uned in the m-audio delta cards. > Steve, I wonder if you have any info on something I was reading in Bob Katz's book recently, that many A/D converters actually have compressors or other sorts of non-linear circuits built into them which effect the use of the converter when it gets anywhere near maximum value anyway. I found some of his comments about what happens with A/D's in these regions interesting. Do the spec sheets you've looked at imply anything like this? Thanks, Mark
