[Richard Crowley]

"David Nebenzahl" wrote ...
Several recent threads here about connecting audio equipment make me
wonder about "line level" connections. I know what they are and where
they're used, but I'm wondering: is there an industry standard for them?

I know that standard line-level impedance is 47K ohms, but what I don't
know is the voltage level specification, if any. I suspect that there's
no one set voltage level, but isn't there a more-or-less standard
*range* of voltages for line level? (My guess, if I had to take one,
would be somewhere around 100 millivolts.)

Not only is there no "line-level standard voltage", but there isn't even
a standard *impedance.* Perhaps the best you can do is to follow the
history of "line level" from telephony 100 years ago and trace the
evolution (or perhaps more properly "devolution").

Now "professional line level" is much closer to having standard
impedances and levels than consumer "line level" which is all over
the map.

When I am building equipment with "consumer line-level" I design
to: 2V p-p nominal, 100-1K ohm output impedance, and 10K
input impedance.

Googling doesn't produce any definitive results here.

Sometimes when Google reports that there isn't anything,
it is telling the truth.