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:
- Standard consumer line-out levels.
- Standard pro line-out levels.
- Consumer line-in levels.
- Pro line-in levels.
- Consumer mic levels.
- Pro mic levels.
- Consumer speaker levels.
- 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.