I am trying to measure a SMSL D400 DAC which is capable of outputting 5 Vrms. I would like to be able to drive the DAC to this max voltage and then step down from there to see the impact on SINAD. The DAC is connected to the computer over USB and I have enabled mirror mode within the QA403.
What I am finding is that using the built-in generator, I do not get to the max value as I increase dbV from 0 to 12. In fact, it stays capped at the value I measure at 0 dbV. What I really want is to send digital codes that are the equivalent of 0 dbFS.
Now, if I switch to REW and generate a 0 dbFS tone (1 kHz), I do measure 5 Vrms on the DAC. What am I missing or doing incorrectly? Thx!
Thx for sharing the relevant graph from the User guide. That explains the clipping behavior. The issue with not being able to reach max voltage is user error! I thought that the volume was set to 100 in Windows as REW was able to get me the max output. Maybe it forces it to max volume. I also thought that I checked this, but when I went back to measure the voltage today, it measured even lower. I then looked at the sound settings and sure enough the volume slider was not set to 100. So, dBV is indeed behaving as dBFS in mirror mode. Thx!
I will say this: Depending on the soundcard (D/A) windows can distort at, or near full level. As a data sample, a Focusrite 2i2 v2 works best just under 100%. IRCC, it was around 96-98%.
