Audio Precision APx516B Review

[Rja4000]

It works! I made a Notch frequency response table and created an EQ file.
View attachment 389980

Did you mesure your actual APU notch response to create this ?
That's what I do: I measured it and use the measurement to build the compensation curve.
Cut is not exactly 30dB, in my case.
You may easily differ several tenths of dB.

 

[johny_2000]

Did you mesure your actual APU notch response to create this ?

Yes, I did. The EQ graph I posted from AP Flex was the actual APU notch response.
The initial measurement was performed in REW according to the manual: make a sweep measurement of a loopback connection firstly with the notch filter in place, then another without it, then use the Trace arithmetic feature of the All SPL graph to generate (notch response)/(no notch response) and export that result as a text file to be loaded as a mic cal file.

That's what I do: I measured it and use the measurement to build the compensation curve.
Cut is not exactly 30dB, in my case.
You may easily differ several tenths of dB.

Mine was very close to 30dB, so I manually rounded some frequency bands and also made a leeway of 995...1000...1005Hz with 0dB gain
Then I converted it to a CSV Excel spreadsheet, imported it into AP Flex EQ and inverted it there.

 

[johny_2000]

@Rja4000,
Now I've achieved that APx500 Flex, REW and Multitone Analyzer measure almost the same THD, THD+N, SNR, SINAD, H2/H3 etc. of the same DUT both in unweighted and A-weighted mode. The difference is only a few tenths after the decimal point: -118.3 ... -118.5 ... -118.7 dB. And all of them are able to use the APU Notch calibration file to adjust the measurement report!

 

[Rja4000]

@Rja4000,
Now I've achieved that APx500 Flex, REW and Multitone Analyzer measure almost the same THD, THD+N, SNR, SINAD, H2/H3 etc. of the same DUT both in unweighted and A-weighted mode. The difference is only a few tenths after the decimal point: -118.3 ... -118.5 ... -118.7 dB. And all of them are able to use the APU Notch calibration file to adjust the measurement report!

The difference is how they are doing their internal notch filt
er.
APx is simulating an analog filter, while I suspect the others are just dropping bins.
With the APU, it should make little difference.
Without it, it's another story.

The biggest difference is with IMD, since APx is using a very specific bandpass filter.

I measured the APx notch and bandpass filters.

 

[Grooved]

I was able to run the APx500 Flex with two different ASIO devices for output and input. FlexASIO worked with this:
View attachment 389897
Overall (IMO) AP Flex doesn't offer anything better than REW and Multitone Analyzer for hobbyists.
View attachment 389898
AP Flex software does not allow use of a frequency response calibration file for an external AES17 Notch filter.
So, actual SINAD (no-wt) = 88.3 dB + 30 dB(Notch) = 118.3 dB. Meets DUT specifications.

I don't understand why you didn't simply use the RME ASIO driver in the Output configuration of APx500 FLEX, and the Comtrue ASIO driver for the Cosmos ADC in the Input configuration part.
It would avoid using ASIO between APx500 FLEX and FlexASIO and WASAPI between FlexASIO and both devices

What was the reason of using FlexASIO?

Yes. FlexAsio or Asio4All.
I think Amir is using ASIO4ALL from time to time.

I don't like either.
The issue is that You can't set 2 different sampling frequencies, anyway.

And if you use FlexASIO for the input part and ASIO4ALL for the output part, shouldn't it work?

 

[johny_2000]

I don't understand why you didn't simply use the RME ASIO driver in the Output configuration of APx500 FLEX, and the Comtrue ASIO driver for the Cosmos ADC in the Input configuration part.
It would avoid using ASIO between APx500 FLEX and FlexASIO and WASAPI between FlexASIO and both devices

What was the reason of using FlexASIO?

In AP Flex, you can only select one device for input and output. If I select RME ASIO, I have to use its inputs and outputs. If I select Comtrue ASIO, I have to use it for inputs and outputs (which it does not have). That's why I have to use FlexASIO as a single device for input/output in AP Flex, and then use FlexASIO settings to assign different input and output devices.

 

[johny_2000]

And if you use FlexASIO for the input part and ASIO4ALL for the output part, shouldn't it work?

Same thing. You can't use two different devices for inputs and outputs.
If you select FlexASIO on the input side, it will automatically select it on the output side, and vice versa.
Same for ASIO4ALL and any other devices.

 

[Grooved]

Thanks @johny_2000 , I thought that APx500 FLEX was allowing to select two drivers, especially as it's not linked to a AP device

 

[johny_2000]

Thanks @johny_2000 , I thought that APx500 FLEX was allowing to select two drivers, especially as it's not linked to a AP device

No, that's limitation #1. And limitation #2 (mentioned by @Rja4000) is the inability to select two different sampling rates for input/output, which is why some DUT tests have a poor picture of what's going on.

 

[restorer-john]

No, that's limitation #1. And limitation #2 (mentioned by @Rja4000) is the inability to select two different sampling rates for input/output, which is why some DUT tests have a poor picture of what's going on.

It’s not a limitation, it’s a feature.

 

[johny_2000]

It’s not a limitation, it’s a feature.

Thanks! This has convinced me to use other audio analysis softwares that are not only free but don't have these features.

 

[bmsorin]

Fully agree !

And there really is no reason for that.
They could allow different ASIO drivers for inputs and outputs and even different sample rates, and the software would instantly gain a lot more use.

The much cheaper Virtins MultiInstruments allows this, so why not AP ?

And ASIO4ALL is a nightmare to use, indeed.
And still doesn't solve the different sampling frequency issue.

Another point that would be highly beneficial: allow to pause and change scale between the Dynamic range AES 17 measurement.
As is, you're limited by the ADC dynamic range, which is most of the cases less than the DAC's.
What I have to do is use another software and 2 different input gains to measure dynamic range efficiently. Which should be possible with AP.

There are multiple other things I'd like to see improved (like using averages or longer acquisition for bench meters, or adding THD and SNR meters as well,...) , but those are the most penalizing.

Hello,
Forgive my ignorance, but REW allow select different ASIO drivers for INPUT/OUTPUT?

 

[Rja4000]

Hello,
Forgive my ignorance, but REW allow select different ASIO drivers for INPUT/OUTPUT?

Nope.
But you may start 2 instances of REW

And REW is not really meant for sweeps, unlike AP
For sweeps, the same software has to control output and measure input.

 

[pma]

It is possible to use ASIO4ALL or Wasapi Exclusive with REW. Then it works with 2 different audio converters.

 

[Rja4000]

It is possible to use ASIO4ALL or Wasapi Exclusive with REW. Then it works with 2 different audio converters.

Yes, and that also works with APx Flex.
What does NOT work is to select 2 different sampling rates. So some of Amir's standard measurements are not possible.

With an AP hardware, it is possible, since the input or the output may be analog.

 

[phofman]

It is possible to use ASIO4ALL or Wasapi Exclusive with REW. Then it works with 2 different audio converters.

While in Wasapi excl both directions run mutually independently, ASIO passes equal-length buffer of data from IN and OUT in one ASIO call, making the combination of two unsynchronized soundcards problematic. It may or may not work OK, depending on the actual difference of the two independent clocks.

 

[morillon]

it seems to me that multitones allows you to choose asio wasapi inputs or outputs difrerent machines, and is very suitable for sweeps..
after in practice?
maybe on a case by case basis?

 

[phofman]

It is possible to program the application to use multiple independent ASIO connections - e.g. hacking the ASIO host library to move the connection variables from static context, or using multiple processes in the app to load the ASIO library multiple times - e.g. https://www.diyaudio.com/community/threads/diana-a-software-distortion-analyzer.315785/post-7121977 . But it's a major hassle.

 

[Rja4000]

It is possible to program the application to use multiple independent ASIO connections - e.g. hacking the ASIO host library to move the connection variables from static context, or using multiple processes in the app to load the ASIO library multiple times - e.g. https://www.diyaudio.com/community/threads/diana-a-software-distortion-analyzer.315785/post-7121977 . But it's a major hassle.

But it's probably easier if sampling frequencies are multiples and buffer size is chosen accordingly.

 

[morillon]

Post in thread 'Beta Test: Multitone Loopback Analyzer software' https://audiosciencereview.com/foru...loopback-analyzer-software.27844/post-2077598
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