Re: [LAD] [ot] rme fireface: weird balanced output measurements

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To: <linux-audio-dev@...>
Date: Friday, February 17, 2012 - 10:55 pm

On Fri, Feb 17, 2012 at 12:32:01PM -0500, gene heskett wrote:

> [bolometers]

The average house & garden multimeter is indeed completely useless
for measuring anything audio. OTOH

* There are quite good handheld audio RMS meters which don't
cost a fortune (but they are in the higher price range).
They use analog integrated circuits which can be quite
accurate - at least for normal audio use. They are not
laboratory standards of course.

* Any pro-quality audio card, once calibrated against a known
signal and combined with some simple software will make a
near-perfect RMS meter *for the audio band* and as long as
you don't drive it into clipping.

> [cable impedance]

The concept of cable impedance makes sense only if the lenght
becomes a non-trivial fraction of wavelength. For audio that
means that for anything shorter than a few hundred meters it's
only capacitance that matters. And yes you need hefty line
drivers and low output impedance to push 20 kHz, +20 dBu on
a long line. Which is one of the reasons why real pro quality
analog audio remains expensive.

Ciao,

--
FA

Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl.

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Messages in current thread:
[LAD] [ot] rme fireface: weird balanced output measurements, Jörn Nettingsmeier, (Fri Feb 17, 12:32 pm)
Re: [LAD] [ot] rme fireface: weird balanced output measureme..., Fons Adriaensen, (Fri Feb 17, 10:55 pm)
Re: [LAD] [ot] rme fireface: weird balanced output measureme..., Jörn Nettingsmeier, (Sat Feb 18, 12:45 pm)