David I. Emery wrote: > It is quite surprising that the 859xE series is spec'd about > 10-15 db worse on phase noise than the comparable 856xE instruments. I > wonder if this difference exists in the performance or just marketing > domains and what the actual differences are in the implementation that > accounts for it. > > Most of the phase noise originates in the local oscillator, the cost can be reduced by using a lower performance oscillator. > I might also add that many of the cheap 24 bit 96/192 Kbs USB > sound input devices actually use codec chips which are DC coupled > internally all the way to the input pin though that is usually > referenced to half the analog supply voltage (3.3V/2 typically) rather > than 0. So going all the way to DC with one of these chips is not > impossible with external non-audio signal processing feeding the analog > input pin, thus removing the 20 Hz high pass from the audio preamps > ahead of the codec chip. > As long as any internal digital high pass filter is bypassed and the idle tone performance is satisfactory (more likely with a multibit modulator) with a dc input.
Bruce _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
