Analog Disovery as Audio Analyzer

[jaxbird]

Example of how to read the THD+N vs Power chart, lots of information can be obtained from a plot like this:

[jaxbird]

OK, here is a download link:

http://www.thestuffmade.com/audioanalyzersuite/publish.htm

I'm interested in knowing about any bugs you find, pm me or just post here in this thread. I haven't fool proofed the software yet, so if you write e.g. "dave" in start frequency, it will likely blow up. Or if you try run multiple measurements at the same time it will blow up, but in general it should be usable.

I am only able to test with my version of the Analog Discovery, so any reports on compatibility are appreciated.

Note: the spectrum analyzer is not yet implemented. If that annoys you, I can hide the tab. Feature should be available before new year.

[jaxbird]

Connections part1:

[jaxbird]

IMD measurement connection:

[jaxbird]

Output Impedance:

[jaxbird]

Input impedance:

[jaxbird]

And of course Merry Christmas to everyone 





If you are not feeling it and you need to get in the mood:

[fpliuzzi]

Thank you very much for making your Audio Analyzer Suite available here. Merry Christmas and a Happy New Year to all.

[mtdoc]

Excellent Jaxbird. 

I have no immediate use for this but it will be fun to play and learn with and it's great to see someone making use of the ADs full potential.  I think it's a remarkable little piece of hardware.

Merry Christmas to you!

[jaxbird]

Thank you very much for making your Audio Analyzer Suite available here. Merry Christmas and a Happy New Year to all.

Thanks, Merry Christmas to you and your family, hope you having a great time.

Cheers

[jaxbird]

Excellent Jaxbird. 

I have no immediate use for this but it will be fun to play and learn with and it's great to see someone making use of the ADs full potential.  I think it's a remarkable little piece of hardware.

Merry Christmas to you!

Many thanks, Merry Christmas to you and your loved ones.

You can use this with any kind of amplifier, from simple opamps to high power amplifiers and tubes etc. It's really just something I felt was missing from the official software provided with the analog discovery. Just to make it easy for everyone to obtain common amplifier performance parameters.

[jaxbird]

I hope everyone got some understanding that working on this project has been delaying my promised release of the Analog Discovery Impedance Analyzer (arguably a much more generally valuable product) I know I promised a swift release, apologies about the delays, I will release very soon. It is just a lot more complex than the audio analyzer, so I think the audio analyzer is a good way to test the deployment.

https://www.eevblog.com/forum/projects/impedance-analyzer-build-and-experiments/135/

[Mark]

Hi jaxbird, I just downloaded your software and look forward to using it, I have found the Analog Discovery to be a most useful box of tricks since getting one for Christmas last year.  I am currently working on an amplifier so I will have a chance to try out your software next week (when I repair the amp... I released the magic smoke!).  It's a 50W amp running up to 500kHz. 

Thank you, Merry Christmas and a Happy New Year!

[Zero999]

In essence what you are saying is that there is no point in standardized testing of amplifiers as using resistive loads are not equal to speaker loads.

Yes.  Did you follow the suggestion to run a simulation with different kinds of loads?

You seem persistent, so let's do a little experiment, instead of a simulation, to find out how much difference there really is and what it looks like.

Here is a comparison between using a typical small 2 way speaker with an impedance between 5 Ohm and 20 Ohm, compared to a 6 Ohm resistive load.

2 Way speaker's impedance for reference:



6 Ohm load resistor's impedance: (not very exciting)



Distortion measurement with Speaker load:



Distortion measurement with Resistive load:





The only difference here is that the amplifiers distortion is actually overall lower with the speaker load Especially at the frequencies where the speakers impedance is higher.

Just a couple of questions.

Presumably those plots were taken from the voltage on the amplifier output, not from the sound from the speaker.

If the speaker's impedance varies at different frequencies then doesn't the power dissipation and thus output vary significantly?

If you plotted the real power dissipated in the speaker, you'll probably find it varies hugely as the frequency is changed. Does that mean the output will be distorted by the same factor?

[nfmax]

Just a couple of questions.

Presumably those plots were taken from the voltage on the amplifier output, not from the sound from the speaker.

If the speaker's impedance varies at different frequencies then doesn't the power dissipation and thus output vary significantly?

If you plotted the real power dissipated in the speaker, you'll probably find it varies hugely as the frequency is changed. Does that mean the output will be distorted by the same factor?

A1: Yes, the power supplied by the amplifier to the speaker does vary with frequency, a lot. Importantly, it can be reactive power: a capacitive or inductive speaker impedance will simply sling the power right back into the amplifier (which must dissipate it, as heat).

A2: The sound output from the speaker does not vary nearly so much. Speakers are designed so that the sound output (usually measured as sound pressure level, on-axis and 1m from the speaker) is proportional to the voltage on its input terminals. The transduction efficiency, and hence the current drawn from the amplifier, varies with frequency, but this should ideally not affect the output SPL. Usually the variation with frequency depends on the resonant frequency of the various drive units and enclosures within the speaker. Transduction becomes more efficient close to a resonance - though resonances bring problems of their own. The directivity of the speaker also varies with frequency: this may show up in the impedance curve, but even if it does not, varying directivity with frequency means the off-axis frequency response may be anything but flat!

All these effects are, in principle, linear and so do not constitute harmonic distortion. Speaker distortion is usually much worse than that of the amplifier, maybe around 1%, though the very best electrostatic speakers (like the Quad ESL63s I'm listening to now) are down around 0.1%.

Max

[Mark]

Hello,

I installed it on my laptop and could not find a RUN button, so I assumed it was a screen width issue (win7).  I installed it on my main PC and still could not find a run button (win7).  I then installed it on my win10 machine and still no RUN button...  am I doing something wrong?

[sportq]

Hello,

I installed it on my laptop and could not find a RUN button, so I assumed it was a screen width issue (win7).  I installed it on my main PC and still could not find a run button (win7).  I then installed it on my win10 machine and still no RUN button...  am I doing something wrong?

I had exactly the same problem on my Windows 10 64bit system.

Pete

[mtdoc]

Jaxbird, you're not alone. I just happened to stumble upon Japanese audio analyzer project for the AD

[Selectech]

Same issue here,no Run button. Tried on Win 10 x64 and Win7 x64. AD unit works fine with Waveforms on both machines.

Dave

[AudioGuy]

This thread was recommended from another forum.  I'm excited to see where this leads...  Jaxbird, keep up the good work.

[kasey197]

Keep it going jaxbird this is really fabulous !

The one thing i wonder about is the lack of balanced outputs - i know that jaxb's posted a SE to balanced converter but i wonder if we can also make use of the two independent waveform generators ?
If these can be linked does the UI allow us to set one output to be 180 degrees vs the other ?
Haven't actually got my AD yet so cant try it out but praps one of the boffins here knows ...

Great stuff again chaps

[braddrew0]

Nice one jaxbird, love what you've done.

As a complete novice at audio (but one that's very interested) how does this compare to something like the Prism dscope?


Thanks!


Brad

[kasey197]

funny you asked  - I have a prism dscope series iii analyzer
Use it mainly for analogue audio projects.

It costs a bundle  - although still quite bit cheaper than the Audio Precision jobs. Has way better usability than the AP kit and i find it indispensable.

So why am i here playing with the digilent ? Because I need the high bandwidth network analyzer bit. The dscope bw is less than 100kHz...

1K THD performance of the dscope is ca 0.0007% at 80khz BW, THD+N about 0.002% IIRC. Better at 20k bw obviously but plenty low enough for my needs. And probably an overkill for most of us but I have a weakness for test equipment

[Mark]

Has anyone managed to get this working?  If so, what windows version and architecture are you using? 

[fivefish]

Has anyone managed to get this working?  If so, what windows version and architecture are you using?

I got jaxbird software installed on my Windows 10, 64-bit. 

But since I don't have an AD device, when I try to run it, obviously I get an error message "unable to open Analog Discovery Device, make sure device is connected" That's as far as I got until I get an AD.