Anyway, I haven't noticed a difference in trace noise between
the 7A19 and 7A29.
Thanks!
There is no fundamental connection between amplifier input impedance and noise. I've design preamplifiers with sub-300 pV/rtHz, and they could easily have GOhm input resistance. That's because the noise of the input bias resistor is shunted by the (much lower) source impedance.
The relatively high noise of some of the high-Z plugins seems to be mostly a function of their active parts. I've also noted differences between some time bases (e.g. between two 7B80 I have). Apparently one has higher trigger jitter.
Best,
Samuel
