[sdiy] doh! (dB talk-talk)

[media.nai at rcn.com]

>>dBu is dB referenced such that .775V into 600 Ohm is 1 mW,
>>and Decibels are logarithmic so
>>
>>dBu = 20 log (Vrms/0.7746) and
>>
>>Vrms = .707Vpk  (Vpk = Vp-p/2)
>
>I don't believe this is quite correct. What you are describing is dBm, not
>dBu. Just remember that the "m" refers to a "m"illiwatt (into 600 Ohms).

I was describing dBu.

"dBm is a quantity of power where 0dBm is 1 mW across 50 Ohms."

>Up until now I've assumed we were talking dBV, which
>is voltage based and referenced to 1Vrms. Clearly that
>is incorrect. I have to wonder if there is a standard?
>Or are we on our own...

dBu is referenced to .775V
dBV is referenced to 1.0V

0dBu = -2.22dBV = .775Vrms = 1.096Vpk = 2.19Vp-p