Little dude with line levels

[modulay]

I've read this:

Full scale (0 dB on the VU meter) =

+1.8 dBV = +4 dBu = 1.23 V rms = 1.74 V peak = 3.5 V peak-to-peak
for professional equipment

I understand it but, is it valid for both balanced and unbalanced lines?

A balanced line signal is +6dB higher (hot - cold) than unbalanced, then...

+4dBu is referenced to ground in balanced lines?

 

[PRR]

> A balanced line signal is +6dB higher (hot - cold) than unbalanced

No.

Aint no "cold" on a balanced line neither.

 

[modulay]

Sorry PRR but I don't understand well. My english is so bad.

Do you mean that voltaje between hot-cold of a balanced line is 1.23Vrms at full scale (0 dB) ?

 

[JohnRoberts]

Some MI companies provide what they call an "impedance balanced" output. While these outputs aren't differential, so one leg is cold, they do provide some of the CM reduction benefit wrt induced noise like true balanced lines.

This is arguably some of the biggest merchandising bang you can get for adding a penny resistor. :grin:

JR

EDIT differential outputs are capable of 6dB more output level, but should be normalized for same total output when combined at receiver.

 

[modulay]

Is this output stage topology wich you refer,John?



So, in conclussion, my peak indicator should twink when:

1) On a unbalanced out, signal raises 1.23Vrms = sine 1.74Vpeak (single ended).
2) On a balanced out, signal raises 1.23Vrms = sine 1.74Vpeak (differential, or, at least, "impedance balanced").

Is correct?

 

[JohnRoberts]

Yes, that is impedance balanced.

JR

 

[Andy Peters]

[quote author="modulay"]I've read this:

Full scale (0 dB on the VU meter) =

+1.8 dBV = +4 dBu = 1.23 V rms = 1.74 V peak = 3.5 V peak-to-peak
for professional equipment

I understand it but, is it valid for both balanced and unbalanced lines?

A balanced line signal is +6dB higher (hot - cold) than unbalanced, then...

+4dBu is referenced to ground in balanced lines?[/quote]

A balanced signal is always measured between the hot (+) and cold (-) wires. Ignore the ground wire.

A correctly-designed unbalanced output that is specified to have a nominal +4 dBu output will indeed have a +4 dBu output, measured between the output wire and ground. IOW, the unbalanced output and the balanced output have the same output level.

-a

 

[modulay]

Ok.
Thanks to all, folks

 

[Scodiddly]

What PRR meant by "ain't no cold" is that on a balanced signal cable both lines are "hot" - one is positive, one is inverted (negative).

 

[modulay]

Ah ok.
Thanks for explain it

Regards