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xl6009 step up with TDA7492P amplifier problem.

Viliuks

Dec 5, 2015
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Hello!
I have an issue with the boost converter xl6009 and TDA7492P amplifier, when powering on the boost converter the amplifier starts clipping my speakers out, the problem doesn't occur when I don't use the boost converter though.

I need to use the boost converter to power the speakers with 18650 batteries, but I cant really do that if it is clipping.

My guess is that the boost converter fluctuates its output during powerup and the amplifier doesnt correct it, which makes the speakers clip.

Wiring diagram (thanks *Steve*)

poweralt-png.26821
 

Audioguru

Sep 24, 2016
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We cannot help you because you forgot to say how much output current and voltage is needed from the boost converter that might be overloaded.
Speakers impedance? How many amplifiers/speakers? How much total output power is needed without clipping?

Assuming two TDA7492 ICs driving two 8 ohm speakers with a 25V supply then the output power per channel with a small amount of clipping is 32W and the stereo amplifier uses 70W from the 25V which is a current of 70W/25V= 2.8A.
You did not say the input voltage to the xl6009 converter so we cannot calculate its input current. Maybe the battery cells are also overloaded because 70W is a lot of power for a few (how many?) little 18650 cells.
 

Viliuks

Dec 5, 2015
24
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We cannot help you because you forgot to say how much output current and voltage is needed from the boost converter that might be overloaded.
Speakers impedance? How many amplifiers/speakers? How much total output power is needed without clipping?

Assuming two TDA7492 ICs driving two 8 ohm speakers with a 25V supply then the output power per channel with a small amount of clipping is 32W and the stereo amplifier uses 70W from the 25V which is a current of 70W/25V= 2.8A.
You did not say the input voltage to the xl6009 converter so we cannot calculate its input current. Maybe the battery cells are also overloaded because 70W is a lot of power for a few (how many?) little 18650 cells.
Oh man, sorry, I totally forgot about that!

I have 4x18650 batteries wired in parallel, two 4Ω/130w speakers. The power output from the xl6009 is 12v, input is 4.12v form batteries. If connected to external power like 25v, basic boost converter topology means that the boost converter lets the 25v go through it without doing anything to it.

EDIT:
Wierd thing happens, if I turn up the voltage to 20v on the boost converter, the popping dissapears.
 
Last edited:

Audioguru

Sep 24, 2016
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The TDA7492 amplifier produces only about 12W per channel into 4 ohm speakers with a 12V supply. Maybe you want much more power and turned up the volume too high and caused severe clipping.
With a 20V supply the power would be about 32W per channel.

The 18650 batteries are Lithium and are 4.20V when fully charged but the voltage slowly drops to about 3.2V when the load must be disconnected to prevent damage to the batteries.
 

Viliuks

Dec 5, 2015
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The TDA7492 amplifier produces only about 12W per channel into 4 ohm speakers with a 12V supply. Maybe you want much more power and turned up the volume too high and caused severe clipping.
With a 20V supply the power would be about 32W per channel.

The 18650 batteries are Lithium and are 4.20V when fully charged but the voltage slowly drops to about 3.2V when the load must be disconnected to prevent damage to the batteries.
My batteries have over discharge and overcharge circuits on them. And I didn't turn up the volume. But changing the voltage to 20v fixed everything. :)

By the way, how do you calculate the watts per channel?
 

Audioguru

Sep 24, 2016
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Your batteries have "protection" circuits on them which limits their maximum output power and might cause clipping from the amplifier.
The datasheet for the TDA7492 amplifier IC shows a graphs with various speaker impedances. With a 4 ohm speaker it shows about 18W with 1% clipping distortion when the supply voltage is 15V and shows 32W with a 20V supply.
 

Viliuks

Dec 5, 2015
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Your batteries have "protection" circuits on them which limits their maximum output power and might cause clipping from the amplifier.
The datasheet for the TDA7492 amplifier IC shows a graphs with various speaker impedances. With a 4 ohm speaker it shows about 18W with 1% clipping distortion when the supply voltage is 15V and shows 32W with a 20V supply.
You see even if I used external power, which goes through the boost converter and it caused the clipping. The external input is variable 10-30V. Turning up the boost converter to 20v made the clipping dissapear when turning the power on for the amp
 

Audioguru

Sep 24, 2016
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Maybe you do not understand about why an amplifier makes clipping. It occurs when you increase the input level higher than the level where the output swing is maximum. Then the tops and bottoms of the waveform are clipped off. If the supply voltage to the amplifier is increased then its output swing can be higher then the input level can be higher. This sine wave shows clipping:
 

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