- Feb 23, 2016
Yes, most pre's have better EIN at higher gain. How much makes sense to test is more variable. The big thing being condenser micrphones or dynamics and ribbons. I've measured a handful of devices and some lose little EIN down to 20 db gain or less and some lose quite a lot of EIN below or at 40 db. Some that seem good at lower input levels won't take high levels you get with some condensers. So you do want to know where the overload input level lies.Here are some examples
EIN (A weighted) with 150 ohm resistor, 20Hz-20kHz
View attachment 227535
But I think the Dynamic range plot is more "readable"
As an example you see more clearly what the AD8HR is doing.
View attachment 227536
The important thing, in my opinion, is to align "gains" in a meaningful way.
And the only meaningful way is: "I have that mic that gives me that Voltage max for my use case. I want to compare all mic preamps with a gain that is the max gain allowing not to saturate my preamp or ADC with that voltage."
(I decided a threshold THD of 0.1%, but saturation is usually very brutal, so this threshold value doesn't matter much)
Here above, my "reference gain" (0dB) is the max gain to allow 100mV rms input.
(That's about the max level you'll get from a Shure SM58 with a singer in real life)
That's 35dB on the RME (max ADC level at 0dB gain marking = 18dBu) and 44.2dB on the Millenna (45dB gain marking - max output before saturation 27dBu)
For the Yamaha, it's -37dB gain marking (max ADC level for 0dB gain marking is 20dBu).
NB: For fun, I added the RME ADI-2 Pro fs R for its 4 input ranges.
Of course, it can't act as a mic preamp. For this kind of level, you'll need a condenser microphone, that requires a phantom power, and the ADI-2 doesn't have one.
Still, you understand here why you can't get better measurements from the UCX II for mid level signals.
You learn from the above what really makes the difference between an high end mic preamp and a cheaper -but still excellent- one:
The gap is big for LOW gains.
So use in priority such a preamp with high level output microphones (Condenser) or sources (drum kit).
You also realize that it is more meaningful to measure EIN (A) at 30dB gain than at 60dB gain...