dBm, dBu, dBW, VU meter, etc.

[PG1995]

Hi

Could you please help me with this query? I have used this this source for my query.

Regards
PG


Helpful links:
1: https://www.electro-tech-online.com/attachments/dbm2-jpg.75036/
2: https://www.electro-tech-online.com/attachments/dbmv-jpg.75038/
3: https://www.mediacollege.com/audio/monitoring/vu.html
4: **broken link removed**
5: https://books.google.com/books?id=bbNfr_bwUXwC&pg=PA33&dq=volume unit meter&hl=en&sa=X&ei=awz1UfOADqO24ATk4YGICQ&ved=0CEgQ6AEwBQ#v=onepage&q=volume unit meter&f=false
6: https://books.google.com/books?id=kaALAAAAQBAJ&pg=PA159&dq=volume unit meter&hl=en&sa=X&ei=awz1UfOADqO24ATk4YGICQ&ved=0CCsQ6AEwAA#v=onepage&q=volume unit meter&f=false
7: https://www.animations.physics.unsw.edu.au/jw/dB.htm

 

[JimB]

I have never thought much about VU meters until now.

Your Question.

If 0VU = +4dBm and assuming that the scale of a VU meter is truely logarithmic (I am not able to confirm this),

then +3 VU = +4dBm +3dB = +7dBm or 5mW

and -7VU = +4dBm - 7dB = -3dBm or 0.5mW

JimB

 

[KeepItSimpleStupid]

Very odd question and I think it's very hard to come up with a good answer except:

600 ohms is the standard output Z of professional equipment.
Nowadays, no one even cares where 0 VU is. Just listen to any streamed video from multiple sources.

When you grew up in te age of reel to reel or cassette decks, the VU meter was an integral part. All you cared about is that the average level was in range or 0 VU.

Beause of the mass of the movement and the risetime restriction, it might be tough to get your answer.

If you look here: https://en.wikipedia.org/wiki/Rise_time you will find that BW * rise time = ~0.34.

That meter has a constant rise time and therefore the Bandwidth is the parameter that is probably related to VU or better yet Bandwidth per unit time.

I'd guess that some complex math would be required to make a digital VU meter.

The real point is, that only 0 VU matters. Compression or expansion could be empoyed to limit the excursions, but I don't think the relationship your asking for is easy.

Let's say you were monitoring a drum roll and a cymbil crack every 1 sec or so. The drum roll is the average if it lasted forever. The occasional excursions of a cymble every second or so contributes to the loudness perceived.

Anywho, this https://www.google.com/url?sa=t&rct...E7KXkqmmorotuvg&bvm=bv.49784469,d.dmg&cad=rja is an interesting amp with input sensitivity in dbu into 600 ohms.