[mythtv-users] Digital Audio with myth

Steve Adeff adeffs at gmail.com
Mon Nov 28 19:35:36 EST 2005

On Monday 28 November 2005 17:15, Phill Edwards wrote:
> > digital signals don't contain absolute volume levels, only relative
> > within a dynamic range. You can't do normal volume control for an SPDIF
> > signal. You can do range alterations, but then you loose quality.
> This is _waaaay_ off topic now but you guys obvioulsy know a lot about
> this stuff and this looks like a chance to get an answer to something
> I've always wondered about!
> How come on my receiver (and I presume others) does the number on the
> display go DOWN when the volume is being turned UP? I'm just curious.
> Regards and apologies for the hijack!
> Phill

relative decibel level in relation to "max". Max can vary depending on the 
circuit topology of the preamp/receiver.

For instance, many receivers have an integrated preamp in the first amp stage 
so 0 is the max volume level attainable, -3db is 1/2 that power, -6db is 1/2 
the volume a 1/4 the power, etc. (log).

Most(all?) components (read: seperates) like I have use 0 as line level. ie 0 
= input voltage level (usually ~2v depending on the component) and as you go 
down from there its attenuating this voltage lower. Passive volume control. 
My receiver only actively controls the volume of the incoming signal when you 
go above 0.


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