20W Class D Audio Amplifier MAX9744

[verishare]

Hi I'm using your MAX9744 amplifier board in a project. What is the best way to only connect one 4ohm speaker with this amp? Can I bridge the outputs or just use one channel?

Thanks,
Chad

[adafruit_support_mike]

Each channel already uses bridged output, so trying to bridge the channels Would Be Bad.

If you only want to use one output channel, just ignore the other. If you want to convert a stereo signal to mono, you'll have better luck doing that at the input side.

[verishare]

So don't cross the streams. Gotcha.

I have a male to male stereo phone plug with L and R connected together (tip and ring) going to a Pi. And just a single speaker on the Left output and nothing connected to the Right output. Seems to work okay.


Thanks!!

[mrbgfx]

Hi, I know this question has probably been asked a million times already, so I'm sorry in advance but I would like to know what battery you recommend to run this amp?

I saw that you were using a 8 x AA pack in one of the pictures on your tutorials and having done a little research on the most environmentally friendly batteries I found that NiMh came out top. So I bought 8 Duracell rechargable NiMh 2400Mah batteries. The amp works fine, and sounds great. I've also got 2 x 4ohm 30w 4" car door speakers running off it but have yet to test the run-time of this setup. I'm now a bit worried that my choice of batteries might not be up to the job for very long, but my electronics knowledge is limited. I understand that I won't be getting 20w as the max voltage of the batteries is about 10.2v fully charged so from the datasheet it looks like it'll fall somewhere in the 5v output range (2.6/3.6watts), assuming that it steps between 14v/12v/ or 5v mode?

Thanks for any help.

Michael

[adafruit_support_mike]

The main concern is being able to deliver enough current.

We like AAs and LiPo batteries because they can push some serious current.. AAs can deliver up to 2A and most LiPos are designed to be able to discharge safely in 1 hour, making it easy to calculate their current limit from their energy storage: a 500mAh LiPo can deliver 500mA, a 2200mAh LiPo can deliver 2.2A, etc.

The input voltage/output power curves are shown on pages 8 and 9 of the MAX9744 datasheet (https://www.adafruit.com/datasheets/MAX9744.pdf), and it looks like a 10v supply will produce about 10W of output power through a 4-ohm speaker, so the current consumption will be around 1.5A per speaker.