[denotational]

I see, so you want to band-limit the noise, and are willing to accept potentially raising the noise floor in the band-limited range, the idea being that if the original noise is sufficiently broad-band, this will still increase SNR?

[olsondv]

Noise doesn’t have to be broadband. 60Hz is a common noise in US from the AC line frequency. Then there are harmonics of that due to rectifiers.

[denotational]

Fair enough: I was reading the original comment as referring to (thermal) noise intrinsic to the amplifier design itself (as opposed to noise due to imperfections in DC supply or due to coupling with some external transmitter), but this makes more sense, and we should consider the whole system anyway.