That is the way I do it. Play white noise, and then configure the FFT in the analyzer to average a ton (16+ samples). That way, the line doesn't look as noisy. It still won't be a flat line and not good for fractional dB measurements but is the only option.My situation is made more complicated by the fact that I want to test things like smartphone audio outputs where there is no clear way to get the test signal in aside from storing it in some WAV file and playing it.
Hi, I'm new to this forum. I'm a hearing researcher, in need of a quality ADC/DAC device for otoacoustic emission testing.
Specifically, I'm after an ADC with an SNR of >125dB, and a noise floor of less than 4uV RMS.
Basically, I think the QA401 will do the trick, but I just wanted to get some feedback on it before purchasing.
Specifically, does it simply show up as a windows sound device (i.e. does it use Windows API)? I need to use it with LabVIEW.
Also, I see from above a few of you have tried the HiFime isolator without success.. I have a few other USB3 isolators that are much more reliable than the HiFime isolator. I will try them.
Thanks for the above advice. I had been looking at the RME ADI 2 pro... But at >4 times the price, I was hoping the QA401 would suffice. I also appreciate the changing noise floor issue in the 401.The biggest issue with the QA is noise floor modulation. In presence of high signal levels the normally low noise floor rises with signal level. If you only care about the low noise level when only lower signal levels are present it still might work.
The RME ADI 2 pro might come closer to what you want. It will cost more money. It is rated at 120 db snr by them, but they usually are honest. It has variable settings on the input and one of them will likely get the low noise you look for or very close. What you are asking for is near state of the art for an ADC.
Thanks for the above advice. I had been looking at the RME ADI 2 pro... But at >4 times the price, I was hoping the QA401 would suffice. I also appreciate the changing noise floor issue in the 401.
I was just hoping to find a simple ADC/DAC that uses the AKM VERITA chips, but without the additional features (e.g. headphone amp and multi in out) that go along with pricey sound cards like the RME.
why not considering an evaluation board for ak5578?Thanks for the above advice. I had been looking at the RME ADI 2 pro... But at >4 times the price, I was hoping the QA401 would suffice. I also appreciate the changing noise floor issue in the 401.
I was just hoping to find a simple ADC/DAC that uses the AKM VERITA chips, but without the additional features (e.g. headphone amp and multi in out) that go along with pricey sound cards like the RME.
I think it might even be 123dB snr as they can paralell adc inputs. I would agree this is a better option than the 401
Do you have a source for those boards?why not considering an evaluation board for ak5578?
Specifically, does it simply show up as a windows sound device (i.e. does it use Windows API)?
Also, I see from above a few of you have tried the HiFime isolator without success.. I have a few other USB3 isolators that are much more reliable than the HiFime isolator. I will try them.
I wrote a letter to akm and then a local representative contact me. But looks like they only sell to audio company. So if you could get one,please share some information here.Do you have a source for those boards?
Do you think the Knowles is picking up ambient noise which is why it is above the microphone pre EIN? BTW, the RME ADI 2 Pro doesn't have microphone inputs. Also which Knowles microphone are you using? We might be of more help with the specs to it.Thanks all for the input. I know I'm asking for cutting edge tech., and I guess the next step (given the lack of other akm VERITA devices out there) is to see if I can get the AK5397EQ evaluation board - but as pointed out, it will be tricky.
I have (in my lab) 12 different USB & firewire soundcards. All fall 'just' short of what I need (though in fairness I don't have an RME ADI 2 pro)
This is because I use a Knowles LOW noise microphone (for measuring echoes from the ear canal - noise floor of -20dB SPL), that is also used to measure sounds at 100dB SPL. For most of the soundcards I've tested, their noise floor is about 10dB above that of the mic's EIN.
The solution has been to use low-noise mic pre-amps, but you run into headroom issues.
I'm hoping that with modern tech (VERITA ADCs) I can get rid of the preamp, with sufficient headroom to simplify the whole process.
That said, I will see if I can get hold of an RME ADI 2 pro.