On Wed, Jan 08, 2014 at 03:51:41PM +0100, Robin Gareus wrote: > I had calibrated -18dBFS on all of them to the same source (a 1KHz sine, > which I believe to be 0 dBu). That's how I found out about the rubber > controls effect in the first place. O dBu ? So you measured the line inputs, not the mics ? On a real pro device the line input would bypass the mic preamp. OTOH, on most cheap cards it's just attenuated and fed into the preamp - the perfect recipe for bad S/N. > I also did two another measurements, setting the gain-dial of each > devices at minimum and maximum. The 18i6 still came out worst.. but that > is not too unexpected. The gain range of the 18i6 is about -10dB .. > +30dB (per specs it should be -10..+36), while on the other two it's > -20dB .. +20dB. 'Gain' for an A/D converter is not really defined - the ratio of a purely numerical value (in the digital domain) and a physical one (the actual input voltage) is has a physical dimension (1/Volt). So that is not a 'gain' in the usual sense. For a 'gain' spec to have any meaning at all * it should be the analog gain from the input connector to the analog inputs of the converter chip (but don't assume that is what the specs mean), AND * you need to know the actual full scale voltage of the converter chip. Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow) _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
