From: BlueChip <cs_bluechip_at_webtribe.net>
Date: Thu, 03 Jun 2004 19:17:17 +0100

>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

Yes, dB ...what a totally useless term.

Sadly I have a hoard of Micronas documentation and don't recall reading
anything that gives any more information about this than that found on page
45 of the Datasheet which can be found on the Rockbox docs page.

I don't recall which doc contained the gem that "0dB" produced "Line Level
Output", but as it concurred with two real life tests it seems acedemic really.

I believe the last test was performed by comparing the output of the
jukebox with that of the "line level output of my car cd player" ...perhaps
this guy (steve was it?) could offer something more helpful.

My guess is dBv, as I understand the most common definition of Line Level
to be "1V peak to peak".

You seem to be quite knowledgeable ...do you own or have access to a scope?

As for the reference sound level - I'm guessing that'll be some internal
DAC thing.

For now, I am content to ride with the official MAS docs ...but if they are
wrong, and it wouldn't surprise me, then we can tweak the code quickly enough.

> > ============================================
> > What is the VOLUME range you use most often?
> > ============================================
>
>Sorry to chime in late -- just catching up today. I use:
>
>55 - 62 with headphones in bed at night
>72 - 75 with headphones during the day when it's fairly quiet around
>82+ when it's noisy around, and in the car through cassette adapter.
>
>Hope this helps!
>Leslie

Added - thanks ;)
...More good news :)

>Sorry to contribute late. Headphones as low as 45% when going to sleep. (I
>couldn't use the original Archos at all for this purpose because the volume
>didn't go low enough!!).
>Matt

I've added your vote to the graph as 45..54

Rockbox 45% = 127*45/100 = 57MAS -58dB

The algorithm I've settled on goes down to -61dB with accuracy, so ...<phew> ;)

I'm amazed that the original Archos scale only ran from Rockbox 50%...92% -
there aren't 100 discreet steps between those numbers - LOL

Thanks all,

BlueChip

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Received on 2004-06-03