On Wed, Feb 17, 2010 at 11:55:17AM +0000, James Courtier-Dutton wrote:
On 16 February 2010 23:56, Lennart Poettering <mznyfn@0pointer.de> wrote:
The reason I was asking how Jaroslav chose the 0dB position for his measurements was purely because I wanted to do my own measurements for that Aureon card. The dbmeasure tool I wrote for stuff like that puts 0dB at max amplification, however Jaroslav didn't, so I was wondering how he chose 0dB then.
Lennart
I think the digital side is clear. So I will not go into that.
I think we need to separate the analogue side into a number of categories: 1) Standard consumer line-out levels. 2) Standard pro line-out levels. 3) Consumer line-in levels. 4) Pro line-in levels. 5) Consumer mic levels. 6) Pro mic levels. 7) Consumer speaker levels. 8) Pro speaker levels.
There's also headphones there, though for both speakers and headphones it's questionable if we want to do anything.
On the analogue side, I believe the 0dB gain point is intended to be the point at which one can be fairly sure that the distortion will be low for a sensible full scale input.
Generally 0dB is pass through (which does also tend to be the optimal performance point). Actual expected gain levels will vary depending on application - for example, a microphone input will usually need an amplifier with fairly high gain in the path to get the signal to a level usable by the rest of the system.