QuantAsylum QA400 and QA401

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#2,001
davada said:
It's not really an issue. It's part of windows security and one can turn it off when needed.
Bigger question is why are the driver not signed as they should be.
Click to expand...

I read that Howtogeek link of yours and I'm unclear if after installing the unsigned certificate whether after the subsequent reboot, with Windows 8/10 x64 security fully back on, the failed certificate still works or is again rejected?
 
#2,002
MarkS said:
I read that Howtogeek link of yours and I'm unclear if after installing the unsigned certificate whether after the subsequent reboot, with Windows 8/10 x64 security fully back on, the failed certificate still works or is again rejected?
Click to expand...

I had the same trouble with the QA USB driver. I used the procedure linked to and it worked for me.

Don't know. I didn't turn the security back on.
 
#2,010
agdr said:
Looks like it does, if I'm looking at these right! In the plots below I've expanded the log and linear axis from the 20Hz - 20KHZ default to 20Hz - 96KHz. The QA401 parameters are set at the 192Ksps, 65K window and -10dBV. The unit is in loopback on the right channel, since that is apparently the "good" channel at 192Ksps.

* I was curious about the frequency response before starting the tests. So the first is the QA401 frequency response plug-in setup going from 20Hz to 96KHz in 1KHz steps and the second plot is the results. Looks bad at first, but Excel has it scaled so the entire vertical axis just goes from -49dBV to -53dBV and the variation goes from -50.5 to -53.5. It is actually fairly flat if I'm looking at the correctly.

A note of caution to anyone doing frequency response tests on the QA401: the (V1.47 here) software does not reset the generator parameters back to where they started! If you look at your generator at the end the params will be whatever the freq response test stepping ended with.

* The next two are log and linear plots with the tone at 19KHz. I can see the harmonics at 38KHz, 57KHz, but 76KHz & 95KHz are gone. I'm assuming those missing two highest harmonics are a "real" lack of harmonics and not an analyzer deficiency up there since I'm seeing other harmonics at 84KHz and 87KHz (appears to be working up there).

* The next two are log and linear plots with the tone at 10KHz. I can see the 20KHz & 30KHz harmonics with the higher ones gone again.

* Next is a 5Khz tone just to pick something more or less random out of curiosity.

* Next is a 1KHz tone as a double-check that nothing has changed. 🙂 The 2nd and 3rd are still where they were in the posts above for the 192Ksps and the right QA401 channel.

* The last two are the setup screens for changing the axis and THD measurements to 96KHz from 20KHz, for anyone wanting to try replicating these on their QA401's.
Click to expand...

And the THD numbers ? There are only FFT without THD percent.
 
#2,011
agdr said:
Looks like it does, if I'm looking at these right! In the plots below I've expanded the log and linear axis from the 20Hz - 20KHZ default to 20Hz - 96KHz. The QA401 parameters are set at the 192Ksps, 65K window and -10dBV. The unit is in loopback on the right channel, since that is apparently the "good" channel at 192Ksps.

* I was curious about the frequency response before starting the tests. So the first is the QA401 frequency response plug-in setup going from 20Hz to 96KHz in 1KHz steps and the second plot is the results. Looks bad at first, but Excel has it scaled so the entire vertical axis just goes from -49dBV to -53dBV and the variation goes from -50.5 to -53.5. It is actually fairly flat if I'm looking at the correctly.

A note of caution to anyone doing frequency response tests on the QA401: the (V1.47 here) software does not reset the generator parameters back to where they started! If you look at your generator at the end the params will be whatever the freq response test stepping ended with.

* The next two are log and linear plots with the tone at 19KHz. I can see the harmonics at 38KHz, 57KHz, but 76KHz & 95KHz are gone. I'm assuming those missing two highest harmonics are a "real" lack of harmonics and not an analyzer deficiency up there since I'm seeing other harmonics at 84KHz and 87KHz (appears to be working up there).

* The next two are log and linear plots with the tone at 10KHz. I can see the 20KHz & 30KHz harmonics with the higher ones gone again.

* Next is a 5Khz tone just to pick something more or less random out of curiosity.

* Next is a 1KHz tone as a double-check that nothing has changed. 🙂 The 2nd and 3rd are still where they were in the posts above for the 192Ksps and the right QA401 channel.

* The last two are the setup screens for changing the axis and THD measurements to 96KHz from 20KHz, for anyone wanting to try replicating these on their QA401's.
Click to expand...

And the THD numbers ? There are only FFT without THD percent.
 
#2,013
401 - Balanced and un-balanced behaviour

Can anybody suggest a location for information on proper connection to the 401 when unbalanced circuits need testing?

Input:
Being a differential input I assume that the analyzer could be considered "floating" thus the centre pins of the BNC's can be freely connected to 'hot' or 'ground' of the unbalanced circuit

Output:
This is the old bogey of electronic output, long live transformers! 🙂
- If only one BNC (and its shield,) is used what is the level?
- If the two BNC centre pins are used what is the level?
- If the shield of an output BNC is shorted to its centre pin what is the level (and prospect of damage)

Disclaimers
1. assume no DC voltage / over voltage involved
2. I have ordered my new unit (exciting) but it hasn't arrived yet!
 
#2,014
I suggest to scan through the QA401 users manual. Specifications and questions regarding the input and output capabilities are pretty much all explained.

For unbalanced testing I simply terminate one of the inputs and utilize the remaining BNC. I don't think you need to connect your DUT ground to the BNC center of the other input to get acceptable measurements.

Dave.
 
#2,015
Thanks,
Inputs are easy - its the manner that the outputs work is the more ambiguous case and the manual is not all that forth coming with correct practice for driving unbalanced loads. Using just one BNC would be obvious but I assume the level would then be 6dB low (given it is 'one-legged')
 
#2,016
Yep, just use a single output.

6db low...relative to what? 🙂 You can set the output amplitude however you like....within the specification maximum.
The output resistance is 47 ohms. An excellent value to both provide accidental short-circuit protection and decouple capacitive loads.
Check on page 8 of the manual. "Electrical Characteristics of the Connectors."
 
#2,017
Thanks.
Re my comment - 6dB low; if the signal was sourced from a differential output pair, for any given output level ("the reference level") the voltage from only one of the BNC would be half of the total voltage across the differential pair, hence my comment, that unbalanced level (using one BNC) would be 6dB low from the "reference level".

I seem to remember seeing - many days back (read OP71 days) a topology for dual op amp creation of balanced outputs. Due to clever feedback application shorting to ground of the pin3 output increase the Pin2 output voltage by 6dB - thus the unbalanced output level always equalled the balanced level.

And for the record I refer to pin2/pin3 in the XLR/AES standard not the actual pins of the OP71!

Denis Bohn - if he is on this forum would be an expert on this.

Sound System Interconnection is still one of the best around imho
 
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