Arduino NANO 33 iot (3.3V) vs audio

KeithWalker

Joined Jul 10, 2017
2,351
What do you mean?
Do you know what the output is on an Arduino analog output pin? It's a constant amplitude, pulse width modulated (PWM) signal. Do you understand how a class D amplifier works? It turns the analog input into a PWM signal.
If you plan on amplifying a PWM signal with a class D amplifier you need to smooth the signal out or you will get some rather strange interference between the two switching frequencies.
 

Thread Starter

Lucky-Luka

Joined Mar 28, 2019
173
Do you know what the output is on an Arduino analog output pin? It's a constant amplitude, pulse width modulated (PWM) signal. Do you understand how a class D amplifier works? It turns the analog input into a PWM signal.
If you plan on amplifying a PWM signal with a class D amplifier you need to smooth the signal out or you will get some rather strange interference between the two switching frequencies.
OK...
I have said that I intend to use a class AB amplifier (to avoid the problem you just mentioned)
 

Audioguru again

Joined Oct 21, 2019
4,675
The Unisonic datasheet from Taiwan says that the true power from a TDA7377 class-AB amplifier is 13.5W into 4 ohms per stereo channel at low distortion when its supply is 12V. Then its output is 20.8V peak-to-peak. Its gain is 26dB which is 20 times then its max input is 20.8V/20= 1.04Vpp which is 368mV RMS.

The datasheet from Unisonic and its copy from Cotec/STmicro do not show the frequency response so maybe it is no good for audio.
 

KeithWalker

Joined Jul 10, 2017
2,351
The Unisonic datasheet from Taiwan says that the true power from a TDA7377 class-AB amplifier is 13.5W into 4 ohms per stereo channel at low distortion when its supply is 12V. Then its output is 20.8V peak-to-peak. Its gain is 26dB which is 20 times then its max input is 20.8V/20= 1.04Vpp which is 368mV RMS.

The datasheet from Unisonic and its copy from Cotec/STmicro do not show the frequency response so maybe it is no good for audio.
The data sheet from STMicroelectronics state that theTDA7377 is "2 x 30W dual quad power amplifier for car radio" , so it is good for audio.
 

Audioguru again

Joined Oct 21, 2019
4,675
The data sheet from STMicroelectronics state that theTDA7377 is "2 x 30W dual quad power amplifier for car radio" , so it is good for audio.
The STMicro datasheet for the TDA7377 shows almost no graphs and mentions "a saturated squarewave output" which sounds like a buzzer, not audio. They say low distortion but only when the output is "up to" 10W.
They hide its frequency response probably because it is no good like an AM radio.
 

Thread Starter

Lucky-Luka

Joined Mar 28, 2019
173
This cheap module is perfect for what I have to do (no high definition, no high power) and it's not as bad as mentioned.
 

Audioguru again

Joined Oct 21, 2019
4,675
The old TDA7297 is different to a TDA7377.
The TDA7297 cannot drive 4 ohms car speakers. It might not be available anymore.
It produces 4W per channel into 8 ohms at medium distortion with a 12V supply.

The newer TDA7377 produces 13.5W into 4 ohms at low distortion per channel into 4 ohm speakers with a 12V supply.
 
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