Beta Test: Multitone Loopback Analyzer software

[Rantapossu]

The dBFS unit scaling seems to be 3 dB off when using the unity gain:

There might be issues with other units too, Pavel said on the other thread that he had to change the resistance from 4 Ohms to 2 Ohms to get proper power value with 4 Ohm load.

 

[pkane]

The dBFS unit scaling seems to be 3 dB off when using the unity gain:

View attachment 263841

There might be issues with other units too, Pavel said on the other thread that he had to change the resistance from 4 Ohms to 2 Ohms to get proper power value with 4 Ohm load.

The horizontal scale is based on the measured RMS value. In previous versions it was based on generator values.

 

[GXAlan]

@pkane
I figured out the bug. My HD820 recordings are super short (2 seconds). If I use Multitone with a small FFT, it scales it differently than if I increase the FFT beyond what the actual minimum length is needed.

dBr

 

[Rantapossu]

The "black graph" seems to depend on the sweep start signal level:

-60 dBFS to 0 dBFS when sweeping using the dBFS unit and changing to W unit after sweep (Black graph):

-10 dBFS to 0 dBFS when sweeping using the dBFS unit and changing to W unit after sweep (Works ok):

-60 dBFS to 0 dBFS when sweeping using the Watts unit all the time (Black graph again):

 

[Rantapossu]

It seems that the step 18/61 is the last one that's ok (25,1 uW):

Step 19/61 turns already black (Around 31.5 uW):

 

[Sokel]

Level sweeps are weird.Is autoscaling every step like this:

 

[pkane]

It seems that the step 18/61 is the last one that's ok (25,1 uW):

View attachment 263883

Step 19/61 turns already black (Around 31.5 uW):

View attachment 263884

Thanks for all the testing! I think I understand what's going on. Let me see if I can reproduce and fix.

 

[pkane]

Level sweeps are weird.Is autoscaling every step like this:

View attachment 263886



View attachment 263889

Right. This is by design It'll scale to fit the available data with each new step added.

 

[pkane]

Fixing a few issues and adding a new capability, v1.0.74 preview:

https://app.box.com/s/ue7ll9xmvwogst817x2l1xg09opvgy47

• Fix for level sweep numeric X-axis labels being truncated near 0
• Fix for a blank plot during a level sweep
• Add ability to save and restore sweeps from History (currently only one sweep result can be viewed at a time by putting a check next to it in the history window)

Still working on restoring sweeps from history, more to come

 

[Rantapossu]

Thanks again!

The sweep works ok now when using Watts as unit:

I tried what happens now when my sound card misses the fundamental. This is NOT the bug of MT, it's the bug of my E-MU 0404 without using the "Direct monitor" mode:

Now that's cool! When there's no fundamental, MT measures pW levels and of course draws it as it should do. The behaviour of the graph changed when Pauld changed the level sweep to use measured input level rather than the output level.

 

[pkane]

As an update, the 1.0.74 version I posted yesterday is now posted on the website. No new changes since yesterday, so no need to re-download if you have installed this already:

https://distortaudio.org/multitone.html#download-multitone

Changes in 1.0.74​

• Add: ability to change units (dBFS/dBr/V/W/dBW/dBV) in level sweep horizontal (X) axis
• Add: save and restore level and frequency sweeps from history
• Change: level sweep horizontal axis to use log spacing with non-dB units
• Change: level sweep horizontal axis to show measured (input) RMS values instead of generated
• Fix: ASIO drivers could throw an exception when playback is stopped
• Fix: IMD calculation for two or more tones
• Change: TIM test signals will now use DIN IMD calculation method (ref. last tone)

 

[Rantapossu]

The graph seems to be incorrectly calculated when using the Watts as unit (As Pavel said earlier).

The last measurement of the sweep is 61.29 Watts and the graph shows about 30.65 Watts, so it's exactly half of the real value:

When I change the resistance from 8.5 Ohms (The actual dummy load resistance) to the simulated 4.25 Ohms, the graph is correctly calculated...

... but now the measurement is naturally calculated incorrectly:

The actual output of the amplifier is half of that in reality and it shows in the first measurement.

 

[pkane]

The graph seems to be incorrectly calculated when using the Watts as unit (As Pavel said earlier).

The last measurement of the sweep is 61.29 Watts and the graph shows about 30.65 Watts, so it's exactly half of the real value:

View attachment 264174

When I change the resistance from 8.5 Ohms (The actual dummy load resistance) to the simulated 4.25 Ohms, the graph is correctly calculated...

View attachment 264175

... but now the measurement is naturally calculated incorrectly:

View attachment 264178
The actual output of the amplifier is half of that in reality and it shows in the first measurement.

Remember that the level sweep X axis is the RMS value of the measured value. What you see up at the top is the peak value of the capture.

 

[Sokel]

So the green bar glitch reappeared suddenly,this time in spectrum measurements too and it's more frequent.
BUT,this time I measured the outputs to see if it's real and of course it's not.
It seems to show up more frequently when the play gain is low,but not only:

 

[pkane]

So the green bar glitch reappeared suddenly,this time in spectrum measurements too and it's more frequent.
BUT,this time I measured the outputs to see if it's real and of course it's not.
It seems to show up more frequently when the play gain is low,but not only:


View attachment 264478

Does the green bar appear static/fixed after the measurement (doesn't move or change in any way) or does it appear to be measuring actual noise?

 

[Sokel]

Does the green bar appear static/fixed after the measurement (doesn't move or change in any way) or does it appear to be measuring actual noise?

Yes,it's static,as you see it in the screenshot.

 

[pkane]

Yes,it's static,as you see it in the screenshot.

OK, then it sounds like just a display issue with the level control not clearing after measurement. I'll see if I can track this down.

 

[Rantapossu]

Remember that the level sweep X axis is the RMS value of the measured value. What you see up at the top is the peak value of the capture.

I still can't get my math right...

When watching the spectrum view as a dBFS scale, the graph shows the peak value, right?

And when I calibrate the Voltage, I measure it with my multimeter (Fluke, it should read RMS Voltage) and insert it to the dialog:

Now when I measure the spectrum with a Volt scale, it shows the same Voltage I just added:

Should this show a peak value and not the RMS value I just added to the Voltage Calibration dialog, just like the dBFS view earlier?


If I calculate the 1,41421356237 * 13,246V = 18,73267284715302 V which is my peak voltage (I think) and add it to the Voltage Calibration dialog, the Spectrum view now shows the peak Voltages and the Level Sweep now shows the same (RMS) Voltages as my Fluke multimeter and shows the same Power levels as I calculate from the readings from my Fluke Voltmeter and my clamp Ampmeter on the dummy load.

If I use the RMS Voltage reading of my Fluke to calibrate the Voltage, Level Sweep shows half of the Power calculated from the Volts and Amps of my meters.

Could you please check the code, if the calibration Voltage should be inserted as a peak Voltage and not as a RMS Voltage?

 

[Sokel]

I still can't get my math right...

When watching the spectrum view as a dBFS scale, the graph shows the peak value, right?

View attachment 264587

View attachment 264588

View attachment 264590


And when I calibrate the Voltage, I measure it with my multimeter (Fluke, it should read RMS Voltage) and insert it to the dialog:

View attachment 264591

Now when I measure the spectrum with a Volt scale, it shows the same Voltage I just added:

View attachment 264592

Should this show a peak value and not the RMS value I just added to the Voltage Calibration dialog, just like the dBFS view earlier?


If I calculate the 1,41421356237 * 13,246V = 18,73267284715302 V which is my peak voltage (I think) and add it to the Voltage Calibration dialog, the Spectrum view now shows the peak Voltages and the Level Sweep now shows the same (RMS) Voltages as my Fluke multimeter and shows the same Power levels as I calculate from the readings from my Fluke Voltmeter and my clamp Ampmeter on the dummy load.

If I use the RMS Voltage reading of my Fluke to calibrate the Voltage, Level Sweep shows half of the Power calculated from the Volts and Amps of my meters.

Could you please check the code, if the calibration Voltage should be inserted as a peak Voltage and not as a RMS Voltage?

Peak seems to be the right value for me,in fact is spot on.
E-MU's output is 6.7 dBV (2.163V),Rin is 1.5Kohm,so 3.12mW:

 

[Rantapossu]

Peak seems to be the right value for me,in fact is spot on.
E-MU's output is 6.7 dBV (2.163V),Rin is 1.5Kohm,so 3.12mW:


View attachment 264595

Could you give these measurements (The RMS values):