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Subject: Re: Optimum Audio Levels- 0dB
From: Stu Engelke (engineer_at_nycradio.com)
Date: 2004-06-03


Some definition of 0dB and +12 and _ 60 is necessary. dB by its definition
is a relative scale. 0 is usually what we are referring everything else to.
The last letter in dBv dBu dBm etc gives a clue.

So if you use dBv 0dB is 1 volt coming out of the headphone jack. dBm would
be around .7 V

That is what is so nice about standards. There are so many to choose from.
Stu

At 03:22 AM 6/3/2004 +0100, you wrote:

>Hi guys,
>
>First of all a great big thank you to everybody who replied. You help is
>much appreciated :)
>
>I have read every single response and catalogued them; and will make some
>analysis of the results and tweak the algorithm accordingly
>
>A few comments were made that I should reply to; I have combined them all
>into this 'one big reply.'
>
>>I would REALLY like a setting that produces "line level"
>>
>>Don't wan' no stinkin' karry okie.
>
>"LINE OUT" is there :)
>
>The Empty-Orchestra option is gonna be cool - I'm already dreaming about
>it (the interface, not the singing), but fear my time may be about to be
>torn away from such severe Rockbox development - so it may be a while.
>
>>Headphones: 60 - 70 %
>
>Either you have incredible headphones or I am going deaf - lol
>
>>If you do line level what are you going to define "line" as?
>>-10 is about normal for consumer stuff
>>+ 4 is line for pro stuff.
>>Thats dBu
>
>and
>
>>As someone who has tried to use an Archos in professional applications, I
>>would strongly suggest -10dBu. It's consumer grade, at best.
>
>scope tests:
># Chris Muth reports 90% is the closest match to the line level from his
>car CD player
># I recall a more detailed test (but cannot find the email now) where the
>result was 93%
>...The manual claims that 0dB (on it's scale) will produce line-out
>...this is "about" 92%
>
>So as there have been _two_ tests which I know of, and the average of the
>two is almost exactly what the MAS Engineers claim - I am going to reap
>the experience of the chip designers and the two Rockboxers who got out
>their scopes and call 0dB (on the MAS3587 "VOLUME" scale) LINE-OUT
>
>Hope that satisfies all the points which were raised. If not ...ask more ;)
>
>Cheers again for all your time people,
>
>BlueChip
>
>_______________________________________________
>http://cool.haxx.se/mailman/listinfo/rockbox
>
>
>
>
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Stuart Engelke
WMCA WWDJ NY
201-298-2108

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