Re: Is this a good way to test pre-amp hiss of a digital recorder?

"Mike Rivers" <mrivers@xxxxxxxxxxx> wrote in message
news:1149510895.823230.19710@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

I follow that, this is getting too theoretical for a practical test. A
real mic has varying amounts of noise output depending on its design.
In additon, it's very difficult to acoustically isolate a mic, so you
can't get rid of any acoustic noise that gets converted to output
voltage (seen as noise at the preamp output) because of what a
microphone is suposed to do. So testing with a real mic is out the
window, and emulating a "standard" mic with a resistor probably doesn't
really emulate any real microphone.

Yes, it does, at least close enough to make meaningful comparisons of the
noise levels of preamps. Some mics come remarkably close to behaving like
pure resistances, notably transformerless condensers. Others aren't as
close, but close enough for it to work.

It's a way to standardize the test
procedure, however - if (and only if) everyone used the same procedure,
and the same resistor.

For the most part, everybody does use the same procedure -- replace the
source with a resistor -- and pretty much the same resistor -- either 150 or
200 ohms. The AES probably has a standards document someplace on how to do
this, but meanwhile get a 150 ohm resistor and you can separate the sheep
from the goats in the preamp world quite effectively.

Peace,
Paul


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