TDA7240 distortion at low volumes

[scwhiteley1]

Howdy,

I recently built a few amps using TDA7240 ICs. I used the circuit design from the spec sheet. They seem to work pretty well, but for some reason, when set to a very low volume, there is an audible "scratchiness" to the music. Any ideas what would cause this? I did not use shielded wires to connect the source (iPod) to the amp input. Is this the likely culprit? I'm doubting it's the volume potentiometer itself, but I'm no expert.

here's a schematic of the circuit if you'd like to take a peek:
http://circuits.datasheetdir.com/344/TDA7240A-pinout.jpg

Thanks for all the help!

 

[audioguru2]

Your link does not work.

The TDA7240 was replaced by the TDA7240A. Maybe the "A" version fixed something in the obsolete original one.
It is a car radio amplifier IC, not a hi-fi amplifier. Its distortion is as high as 0.5% which is audible when its output is from 50mW to only 12W into 4 ohms with a 14.4V supply, and is built using the pcb design in its datasheet. If you used a breadboard then it probably oscillates and sounds realy bad. If your supply voltage is less than 12V then there is probably crossover distortion.

Every audio amp needs shielded audio cables for its input.

 

[Hero999]

It could be crossover distortion which is more noticeable at lower volumes.

The link works if you copy and paste it into the browser's address bar.

The schematic is simply copied off the datasheet.

 

[audioguru2]

The TDA7240A amplifier has a broad range of distortion. It is typically only 0.1% but has a max of 0.5% for some of them which is pretty bad.

The bad link does not work with Internet Explorer even if it is copied and pasted:

View attachment 41077

 

[Hero999]

No, copy and paste the link from the page, not the quoted post.

He made a mistake with the url tags which can be used to create links that appear as descriptions rather than a long website address.

For example, click here to Google for BB URL tags.