The measuring equipment used on this website?

[Hayk]

At what sample rate are measured the tested devices?

 

[Soniclife]

Every graph should say, different tests are done at different rates.

 

[staticV3]

At what sample rate are measured the tested devices?

 

[Hayk]

I suppose 48khz and 192khz are the resolutions of the source signals sample rates. My question is the sample rate of the FFT.

 

[staticV3]

I suppose 48khz and 192khz are the resolutions of the source signals sample rates. My question is the sample rate of the FFT.

I don't think Audio Precision even lets you see the sample rate that the Analyzer's ADC runs at, much less configure it.

Edit:
If that's the case (I'm sure @amirm can confirm or deny), then one could still reverse-engineer the sample rate from the FFT's refresh rate, with known FFT bin size and Overlap value.

 

[danadam]

I don't think Audio Precision even lets you see the sample rate that the Analyzer's ADC runs at, much less configure it.

Isn't that what you set in "bandwidth" (at 19:04):

 

[amirm]

I suppose 48khz and 192khz are the resolutions of the source signals sample rates. My question is the sample rate of the FFT.

The correct terminology is FFT points. The dashboard uses 32K points as seen in the display below FFT. Multitone uses 256K due to high sample rate used there. Jitter, I don't remember. Maybe 128K. Different levels of averaging is used on top of this.

Some measurements use custom FFT points to extract the data needed.

 

[Hayk]

On the video in#6, there is filter selection and the bandwidth says 24khz(48khz SR), I want to know what is the maximum SR that the tests has been used.
Most audio ADCs as mine Behringer, are192khz and it is blind to crossover distortion.

 

[danadam]

On the video in#6, there is filter selection and the bandwidth says 24khz(48khz SR), I want to know what is the maximum SR that the tests has been used.
Most audio ADCs as mine Behringer, are192khz and it is blind to crossover distortion.

At the end of this review there is a graph with a broadband spectrum, up to about 1.24 MHz. The sampling rate would be at least double that (I guess 64x 44.1 kHz, so 2.8 MHz).

Review and Measurements of Purifi 1ET400A Amplifier

This is a review and detailed measurements of the Purifi 1ET400A Class-D amplifier module. Company was kind enough to send me a complete, assembled kit consisting of two modules, power supply and case, ready to go. They have not disclosed the cost of the unit. Modules will be available to DIY...

www.audiosciencereview.com

 

[Hayk]

I could only read 90khz BW, that makes the SR of 180khz if it is the same BW on the filter selection block.

 

[danadam]

I could only read 90khz BW, that makes the SR of 180khz if it is the same BW on the filter selection block.

I meant this:

 

[Hayk]

Thanks, this is what I was asking for.

 

[Hayk]

You can see how the measurement is much much different with high resolution compared to the one presented with unmentioned SR.
Look at a harmonic near 1khz about -117db, there is no such in the presented spectrum.

 

[NTK]

The APx-555, at least for the B-series, uses 2 different ADC for different sampling rates. It uses a higher performance AKM AK5394A (max 192 kHz sampling rate) ADC for the lower bandwidth tests, and a lower performance Analog Devices AD7760 (max 2.5 MHz sampling rate) ADC for the higher bandwidth tests.

Archimago had a post detailing the internals of an APx-555B.

A look IN the Audio Precision APx555 B-Series. Thoughts on price and value in audio products.

A blog for audiophiles about more objective topics. Measurements of audio gear. Reasonable, realistic, no snakeoil assessment of sound, and equipment.

archimago.blogspot.com

 

[oratory1990]

I don't think Audio Precision even lets you see the sample rate that the Analyzer's ADC runs at, much less configure it.

Both of these are possible.
The sample rate is set via the "Bandwidth"-parameter in the "Signal Path setup"-section of the APx500 software, where you set the input filters to be used for the signal acquisition.
Depending on the model of APx analyzer you have different sample rates available.

For example, these are the options for the APx517:

And these are the options for the APx555:

 

[Hayk]

If @amirm can measure with 2.5Ms/s, why he chooses low SR as 192ks/s which goes blind for crossover spikes in class D and AB?
The AD7760 can go down to -120db but can give more accurate result for these types of amps.
What concerns me, I will buy a 12bit Rigol scope and measure with the FFT the output signal subtracted by the input to -40db the fundamental, by this I hope to get 19bit resolution, which is down to 0.0001%.

 

[oratory1990]

If @amirm can measure with 2.5Ms/s, why he chooses low SR as 192ks/s which goes blind for crossover spikes in class D and AB?

If you want to measure audible frequencies, then you'll configure the analyzer to only measure audible frequencies.

 

[Hayk]

Crossover distortion generates 5th harmonic but what left after correcting feedback are very short spikes of errors. To catch the peak values of these spikes the sampler rate should be very high.

 

[oratory1990]

Crossover distortion generates 5th harmonic but what left after correcting feedback are very short spikes of errors. To catch the peak values of these spikes the sampler rate should be very high.
View attachment 448266

Sure, but why are you interested in the amplitude of a wave at 1 MHz? That's not relevant for audio. At such a high frequency, any transducer (except for MEMS transducers) will be inductive and have a high enough impedance not to draw any relevant current.

 

[Hayk]

The frequency is 5th harmonic that is 5khz for 1khz fundamental. If the sampler doesn't see the peak, it doesn't measure the 5th harmonic.
It occurs 4 times in a cycle but not in full cycle, the FFT sees half cycle after the beginning and half before the end.