From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Brown Subject: Re: Verifying mixer dB data/Invalid dB data from USB cards, especially Aureon 5.1 MkII Date: Wed, 17 Feb 2010 13:06:23 +0000 Message-ID: <20100217130623.GD2032@sirena.org.uk> References: <20100216143200.GB25489@tango.0pointer.de> <20100216144047.GB10586@sirena.org.uk> <20100216154015.GA612@tango.0pointer.de> <20100216210703.GA18109@tango.0pointer.de> <20100216223938.GA23623@sirena.org.uk> <20100216224212.GA1486@tango.0pointer.de> <20100216233825.GB23623@sirena.org.uk> <20100216235658.GA6766@tango.0pointer.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from cassiel.sirena.org.uk (cassiel.sirena.org.uk [80.68.93.111]) by alsa0.perex.cz (Postfix) with ESMTP id 6E6CF103889 for ; Wed, 17 Feb 2010 14:06:24 +0100 (CET) Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: James Courtier-Dutton Cc: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org On Wed, Feb 17, 2010 at 11:55:17AM +0000, James Courtier-Dutton wrote: > On 16 February 2010 23:56, Lennart Poettering 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.