audio amplifiers testing

Hello Anil

Welcome to E2E, thank you for your interest in our products.
It could be considered a standard measuring our low power audio amplifiers, but the reason is that increasing frequency increases the switching losses and the EMI, and decreases the efficiency of the amplifier.

Best Regards
Jose Luis Figueroa
Audio Applications Engineer | A-Team

Hi Jose Luis Figueroa,

Thank you for the response...

You mentioned about EMI. So how EMI comes into picture ? How is it related with frequency of input signal ?

I can say one more reason that, applying low frequency signal will produce more harmonics in  the frequency response of output in the range of 20Hz-20kHz so that the measurements can be more precise. Is this reason right ?

I have one more question,

         TPA2016D2 is a stereo amplifier. So how to give a stereo input to this device as I don't have 'Audio precision' and I an using Tektronix  AFG3101 to give a signal ?

Regards,

Anil

Hello Anil

I had an error regarding EMI, that is related to output signal frequency.
Regarding low frequency signal, that is right. That could be another reason.
You could generate two signals with a generator or use two generators. Another option is that you use the same signal for both inputs.

Please let me know your opinion or if you have more questions.

Best Regards
Jose Luis Figueroa
Audio Applications Engineer | A-Team

Hello Anil,

I am not an expert to the history of audio, but I have a paper I found on the Internet (because everything you read on the Internet is true!) entitled 'Magnetic Sound Recording.' It doesn't have an author and I don't remember where I found it, but the reason I went looking is due to the question you are asking.

Why 1kHz? Why 10kHz? These are the most often test frequencies listed in audio power amplifier datasheets; e.g., Class AB, D, G, etc.

Apparently, it has something to do with the biasing of the magnetic tape with the recording head. I am going to paraphrase, but the sensitivity of the magnetic tape at 1kHz has the lowest distortion. Apparently this distortion is a mechanism of how non-linear the magnetic tape actually is given the AC recording current with a DC bias.

That's the best I can explain it. Old greybeards who lived and breathed audio forever and a day should be able to tell you more. This is one of those questions like 'Why 50 ohms?' and the historical reason is lost in myths and legends.

EDIT:
And I should say, I believe the use of 1kHz and 10kHz has simply carried over into the "digital age".

-Ken

Hi Jose luis,

Thank you for your answers...

1. I have measured THD+N for the audio amplifier TPA2016D2, and it is mentioned in datasheet that, at high power, THD+N will be more. So what I guess the reason is, at high power the load current is high and so the amplitude of output is also high . So amplitude is changed. That means the duty cycle of the PWM also changes. Change in duty cycle may increase/decrease the distortions. That is why THD+N is high at high power.   Is it right ???   (Load is constant throughout the procedure)

2. How to measure the Dynamic range on breadboard for this amplifier?

Thanks & regards,

Anil

Hi Ken,

Thank you for your response...

As you explained, the magnetic tapes may have the affect of frequency. So magnetic tape based audio systems are analog and in case of digital audio systems, what may be the reason ?

Hi Anil

Yes, that is correct. THD+N increases when the output power is very high.

You can find how to measure different parameters in the next link:  Guidelines for measuring Audio Power Amplifier Performance.

I hope this helps you. Please let me know if you have more questions.

Best Regards
Jose Luis Figueroa
Audio Applications Engineer | A-Team