Class D amp clipping at high source volume

[p373]

Hey everyone,

I'm a bit of noob with audio engineering so pardon any simple concepts I may be missing.

I'm trying to build a low power audio circuit for use in a portable speaker. My current design uses the 20W MAX9744 class D amp from Adafruit(https://www.adafruit.com/products/1752).

I've got it all wired up correctly, but when I play music from my cell phone and I raise the volume close to the top, the music will clip out. When I play music out of headphones or a consumer speaker, it does not clip.

I had a previous circuit design that used an LM386 amp and that had the same behavior, and I thought switching to a class D might solve it.

What can I do so when I raise the volume all the way it does not clip or get distorted.

Thanks for any help and let me know if I should provide further information about the circuit design.

 

[impuls60]

I might be missing something here but it sounds to me that you need more power/ability to play louder. That amp has max rail voltage of 14V which isn't a lot.. To play louder you need a higher working voltage. The tpa3116 handles 25V which gives you the ability to play louder. You don't mention the voltage you are running the chip at, but at least run it at 14V to get the most out of it. Some tda chips works at 36V which is better, and the tas5630 works at some 20 ish voltage up to 50V. Then it becomes a beast🙂
Different classes affects efficiency and how much energy you need from a psu(Watts), and voltage tells you how loud you theoretically can play. This if ofc way simplified.. but when you ask any amplifier to create a voltage higher than the rail voltage is at, thats when clipping occurs. In class D you'll usally hear a lot more noise just before it starts to clip..

 

[p373]

Thanks impuls60, I'm running at 5v which is coming from a trinket pro (arduino clone). Ill try running dedicated power that will be higher voltage.

This is for a diy jambox type of speaker so power efficiency is kind of key. I was hoping to run off a lithium polymer and I believe they most commonly come in up to 5v flavors, unless I'm mistaken.

Maybe class d amp isn't the answer? What amp would sound loud (as loud as a jambox) and not clip when source volume is all the way up and still last a while on say a 2100mAh lipo battery? Strict requirements I know! 🙂

 

[lutkeveld]

Output is voltage limited: Power=Voltage^2/2*impedance. Double voltage to quadruple output. MAX9744 on 12V should be quite loud with most speakers.

 

[impuls60]

If you hook up your lipo to this voltage booster you could play way louder and not clip. You can adjust it to the voltage you need by turning the potmeter. It has 400kHz switching frequency so it will not affect the sound in a bad way. I've had great success with it in my projects. DC DC Adjustable Step Up Power Converter Module XL6009 Replace LM2577 | eBay

 

[p373]

awesome! thanks guys. Just bought 5 of those step up converters 🙂 When they arrive and I get them hooked in, I'll report back.