On Fri, Nov 03, 2023 at 12:34:52PM +0000, Jack Reynolds wrote: > I think the point here is we tested at two different pre-amps > gains, to eliminate that as a potential source of noise. > There was no difference in SNR, indicating the noise is generated > by the capsules and electronics, and not the preamp.
Not having the required info (see below), I can't claim that the conclusion is wrong. But the reasoning behind it certainly is. The Zoom F8 preamps have an EIN of -127 dBu(A) at maximum gain. Not bad, but not exceptional either. And that is the only spec we have regarding EIN. It says NOTHING about EIN at other gain settings, in particular much lower ones. A well designed mic preamp will have its best EIN at the highest gain, and stay close to that value for a range of 15-20 dB below maximum gain. But for some the EIN will rise as soom as gain goes down. As an example, have a look at <http://kokkinizita.linuxaudio.org/linuxaudio/einslide/ein.pdf> This compares the measured EIN of two 8-channel preamps: the Aphex 1788A and the Behringer Pro8, as a function of real gain. At maximum gain the cheap Pro 8 ($200), is actually better than the Aphex ($4000). But not for long as gain is reduced. The 65 dB gain range of the F8 is probably a combination of passive attenuation, real analog gain, and (maybe) some 'digital gain' as well. It's nowhere documented. The gain used for the recordings was 38 dB, that is 37 dB below maximum. The real EIN at that setting is anybody's guess. Until it is actually measured, we just don't know. Even with 20 dB more gain, that is still 17 dB below max. Making all the recordings at the same gain setting just doesn't make any sense. The correct way to do this is to use a sensible gain setting for each mic, and document that. The available recordings do not include the raw (A-format) one for the Octomic with additional gain, and the Ambix ones do not have the 71 dB(SPL) noise signal. So there is no way to really compare them to anything else. Ciao, -- FA _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
