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



Mike Rivers wrote:

Pooh Bear wrote:

100% agreed. The difference Mike talks about must be caused by the noise
component of input bias current. The only way to replicate its effect is to use
a suitable resistor or you're simply ignoring that part of the mic amp's noise.

Numbers. Show me numbers, actual measurement, not calculations. Then,
based on the numbers, I'll tell you whether I care about the
difference. I don't trust my test equipment so I'll have to rely on
someone else's test.

What sort of difference might we be talking about here? 2 dB? 0.5 dB? 6
dB?

The difference between 200 ohms and 600 ohms is the square root of their ratios i.e.
sqrt 3 = 1.73 or 4.8dB. Between 150 ohms and 600 sqrt 4 = 2 or 6dB.

That's just their thermal noise contribution btw.

Graham


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