Topic: ADC performance not as good as spec

Heya!

I'm posting to try to see if there is a quick solution as to the performance of my ADC.
I'm trying to use it for some DAC measurements but am not getting the performance that the spec claims or that others seem to be getting.

Replicating archimago's test from this article for example: http://archimago.blogspot.com/2020/09/m … ck_26.html

He gets THD+N values of around -114dB
I'm only getting -100dB (-107 if I lock sine frequency to RTA FFT and use rectangular window)

I've tried adding a USB galvanic isolator in case noise from the pc was an issue, i've tried having it on a different power outlet, I cannot seem to sort it.

Additionally, I tried measuring a 1khz tone from the soncoz SGD1 dac, which as shown here, has exceedingly low harmonics: https://www.audiosciencereview.com/foru … iew.10295/

However my results were significantly poorer, with my 3rd harmonic barely clearing -120dB.
https://thegoldenone.co.uk/ZxBrjJPWhn.png
I understand that this is still an exceptional level of performance but i'm just not sure why there is such a difference between my unit and archimago's? Especially given as both his pro FS and pro FS R measure so similarly.

I'm struggling to get THD+N of <-100dB even on exceptionally measuring dacs and so my tests are somewhat useless given as they're so far behind others including others who are using an ADI-2 pro in the same manner.

2 (edited by GoldenOne 2021-03-01 05:16:09)

Re: ADC performance not as good as spec

This is the loopback of my ADI-2 showing THD+N of only -101dB (short XLR cable from output of DAC to input, full +24dBu): https://thegoldenone.co.uk/VCeZTxlk8C.png

Re: ADC performance not as good as spec

Another find: there is a weird random spike at 33270hz ONLY in the left ADC channel. this occurs regardless of dac used. And only in the left channel. Something resonating maybe?

https://thegoldenone.co.uk/NdnQkCB3gi.png

4

Re: ADC performance not as good as spec

Please contact Synthax UK. There seems to be something wrong with your device.

Regards
Matthias Carstens
RME