On Nov 18, 9:39*pm, Randy Yates wrote:
* the reference levels for dBu and dBV are 0.775 VRMS and 1 VRMS,
* respectively. Is this correct? Are the reference levels I've given
* here exact?
Exact for dBV, close enough for engineering purposes for dBu.
* 2. Is there a standard for converting from dBFS to dBu?
No. This is a great point of confusion. You can't directly convert
them because they describe different kinds of units. It's like
converting the number of apples in a bushel to the number of potatoes
in a bushel. There are a few conventions, however, but mostly there's
things that you choose for yourself, not a standard to which a
manufacturer adheres. Back when people had VU meters and digital
recorders had readable meter scales and an adjustable input level
control, there was often a mark typically somewhere between -16 and
-20 dBFS on the digital meter that was the recommended point
corresponding to 0 VU. But it's rare to see that any more. If you're
working with 24-bit converters and material with fairly high dynamic
range, I'd recommend 0 VU (at whatever level that represents) provides
a record level of -20 dBFS. But it's up to you.
One other question: is there a specification on the absolute maximum
signal voltage magnitude for a line level output?
No specification or standard, but since most gear you'll find today
operates from a +/- 15 volt power supply, it's rare to find a maximum
output level before clipping much higher than +24 dBu. There are
exceptions, of course.
You'll find some discussion of these issues in the Gozintas and
Gozoutas and Meter Madness articles in the Technical Articles section
of my web site.
http://mikeriversaudio.wordpress.com