I got my QA403 finally out of the box and am trying to get a good baseline on audio measurements. I have a BNC to BNC looped from L+ Out to L- IN and all the other 3 inputs blocked with shorting caps. I am just running from the GUI at 192khz 12 dBV full scale, FFT to 256k, 1khz at 0dBV/1Vrms and getting back an SNR of 76.45dB and THD of -62.95dB. I feel like it should be better than that so I’m probably doing something wildly wrong.
I tried switching cables and even tried an RCA to RCA with RCA to BNC adapters but no dice. I tried a couple differnt USB cables and added a powered USB hub for it as well.
Yeah, that’s not right. I’d start at the beginning and see what’s not right. First, run at 48KHz and short all 4 inputs and see what you get. I’d set attenuation to 0.
If that looks clean then I’d turn the generator up to at most 1/2V and check again. Here’s a loopback with balanced left and shorted right. The generator is set to 200mV and the FFT is 16K here which is plenty.
Hi @turambar517. I see that the voltage you’re using to power the QA403 is too low. I’m reading a value of 3.87 V: this could also cause significant problems with the analyzer’s operation.
