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Technical reasons for measuring THD+N at -1 dBFS?

post #1 of 3
Thread Starter 

When looking at the specs for a DAC I noticed that THD+N were measured at -1 dBFS.  A certain designer whose name cannot be mentioned on this site also measures the same factor at -1 dBFS for 20 Hz and 10 kHz, yet uses 0 dBFS at 100 Hz.

 

Is there a technical reason for this (obviously other than potentially juicing up measurement results)?  I'm aware that anything above 0 dBFS is considered an illegal state.

post #2 of 3

It is because some DACs (possibly including the one by the above mentioned designer) have increased distortion near 0 dBFS, and really bad ones may even clip.

 

With some tricks it is actually possible to generate a test tone at greater than 0 dBFS level, and there are DACs (like this one) that will only clip a couple of dB above full scale, to allow for inter-sample peaks in "loud" music.

post #3 of 3

 I would love to see ODAC being tested at 0DBFS at 20hz and 10khz :) If there is a valid point in doing that


Edited by anthk - 4/14/14 at 10:10am
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