1. A recent ad for the Chord
DAVE D to A converter claims a noise level of -180 dB. How is
this possible? (Theoretically a digital black signal of all zeros
would have zero noise). No electronic circuit could be this low
noise; there is no way to measure it. The output impedance is rated
at .0055 ohm. This does translate to a resistor (Johnson) noise
of -180 dBV. However it could only be achieved with an undithered
signal source , which would be highly distorted. Any real musical
signal will have dither in the recording process and will have a
minimum noise close to their signal to noise specification of -127.5
Also I am skeptical since the electronics must
add some noise to the low output resistance achieved by feedback.
I would like to measure one.
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