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Class D Switching Power Amplifiers and Power D/A conversion

Mean hissing (and static) in 2 Watt Class-D
Mean hissing (and static) in 2 Watt Class-D
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Old 16th October 2009, 12:08 AM   #1
r0b is offline r0b  Germany
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Join Date: Sep 2009
Default Mean hissing (and static) in 2 Watt Class-D


I'm hoping for some suggestions here. I have the following:

-2 Watt Class-D Amplifier Vcc 2.5-5.5V
-2" Fullrange Driver

Now when I connect it all up, there is a heck of a lot of funny noise kinda like hissing, simply annoying. It does not really give much output, but that I was expecting.
The hissing stops when I unplug the source. (Checked with two notebooks (on/off mains), Tv-set headphone out, and battery-powered MP3-player). Also there is not really a difference whether the amp is run off battery or ac-converter. At 6 V (4xAA) it is much worse than at 4.5 or 3V ( I suppose that's because I am at the high end of the specified input range).

The thing has differential and single ended inputs. I suppose I would use single ended in the application with an MP3-Player, right? I checked single ended (GND to GND), differential (GND from the player to In-, signal to In+) and something inbetween (GND to In- and GND, signal to In+) but that did not change much either...

Anybody have an idea how I could get that thing a little less annoying, and a little more music-making?

Or should I just write the things off as "learning-money"? I guess the static it outputs all the time is normal. I would be cool with that, if the hissing was gone. I'll try to write sureelectronics about it also, but reading the answers on their page, I kinda doubt that would be too helpful... Maybe they'll swap the two sets for a TA2024 :P
Although I really want to drive the whole setup with 3-4 AAs.

I just found these amps so darn cute, and wanted to fabricate a birthday project for a friend, but I guess he'll have to wait (or the budget will be way higher than planned).

Thanks for your input

P.S.: Once I get done, I'll post the project here
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Old 21st October 2009, 12:38 AM   #2
r0b is offline r0b  Germany
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Join Date: Sep 2009
Ok, so Sure emails me that the amplifier simply makes that much noise out of nothing. They refunded me however. Awesome service!

Now I've got a whoopin' 8 bucks to spend on some other small amp!

I want it to be powered by (max) 4 AA batteries. Anyone know of anything out there? National Semiconductors has a nice class-d thing, but I think it's smd and also not available anywhere.

I've read something about lm368, but I can't find much more info on that one either. Also I don't have any sources, but I guess I would manage to find some.

Google doesn't really get me anywhere, I get a whole lot 12v amps :/ Simply no room for that!

I would appreciate some chips thrown at me, preferrably without much external circuitry!



P.S.: I got to keep the amps, so maybe someone still has a hint how to quiet them down. They are frikkin' perfect for what I want, except for the funny noises they produce...
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Old 21st October 2009, 06:19 AM   #3
theAnonymous1 is offline theAnonymous1  United States
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Have you tried shorting VI with GND to see if the noise is still there?

IN+ and IN- are the differential inputs. For single ended (like from an MP3 player), VI is the positive input.
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