Troubleshooting Hum & Output in Amplifier Kit with TDA2003

Thread Starter


Joined Feb 15, 2014
I recently purchased this Jameco Kit to make use of an old speaker I had. It's an amplifier which uses the TDA2003 IC and the kit also includes a power circuit that allows you to run and charge a 12V lead acid battery making the speaker portable.

I've assembled the kit (it's my first project involving audio) and I'm encountering some awful sound problems. I've connected it to my bench power supply @12vdc, the speaker and my input, an old DAP. The lead acid battery has not yet been attached.

I'm hearing more hum/buzz than anything else. especially at low volume. When I touch one of the audio channels on the 1/4" input jack with my finger, the sound is more audible. And when I make contact with one of the jack's input channels to the ground/heatsink of the TDA2003 the sound is vastly improved. Video is below.

I've assembled the circuit per the kit's instructions and double-checked solder joints, caps, etc. I'm guessing I have a significant grounding problem, can anyone suggest what I should be checking?



Joined Aug 30, 2007
Sounds like 60 cycle hum to me. That would indicate you need filtering in your power supply . Does it make that noise when it's run on batteries?


Joined Feb 5, 2014
I see 3 potential issues. 1- when you're running on wall power, you're not using the linear regulator, and the only filter you have is the 100mF cap on the input. If your power supply is a simple 1/2 wave rectifier, that will not remove the hum. 2- your audio input has 3 contacts. I assume left/right and ground? make sure those are wired properly, and the ground is common thru out. 3- if your input run is long, or next to power lines, it will pick up the hum by acting as an antenna. The results would be exactly what you describe with the various input manipulations. If I'd have to guess, I'd say a combination of all of the above....