[mythtv-users] Digital Audio with myth
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!
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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