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


Phil Allison wrote:
"Pooh Bear"


In any case it's the resistor figure that's been the norm for decades. Why
worry
about it now ?



** A change to permit "shorted input " EIN figures to become the norm would
be a disaster.

Mic pre-amp designs optimised for this meaningless input condition would
have vastly better EIN figures than commonly seen now.

With ZERO benefit to users !!!

A complete crock of parrot ***.




....... Phil

Pretty much so. Some mics, condensers with active outputs are really
around 100 ohms output impedance. They output more noise than the 100
ohm resistors will. If one gets to -129.5 with the 150 ohm source,
that's about it. My High Speed Mic Preamp gets to -135 E.I.N with a
shorted input, nice but not real world. Best way is to load the input
with a 150 metal film resistor and sweep the noise with the Audio
Precision test set. This will show variations of noise vs frequency.
Some pre's are dominant in the 5~10 k hz area, some have a significant
low frequency noise spectrum due to psu contamination. All of these are
summed with the S/N test but that doesn't show where the noise
dominates.

Jim Williams
Audio Upgrades

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