Solid State Guitar Amp Forum | DIY Guitar Amplifiers

I'm hoping someone can point me in the right direction. I have basic (very basic) skills with soldering iron, multi-meter, etc. My Powerblock has developed a bothersome bit of distortion that is always present even on the cleanest settings and at all volumes. Obviously it's harder to hear at low volumes but if I listen carefully I'm sure it's there. Where would I start looking for the problem? Is there one typical source for such or are there many? It's not worth paying somebody to look at it. That would quickly go beyond it's $ value. But I'd like to learn something more and this seems like a good place to start. And keep it out of the landfill. What would be the first one or two things I should check? Thanks.

Feed it 440Hz 100mV at the input, set all tone controls to 5, master voume to 10, slowly rise input volume/gain while watching speaker out.
You should *see*  any dostortion you can *hear* .
After it is confirmed distorting, post screen capture here for us to analyze.
http://www.mediacollege.com/audio/tone/files/440Hz_44100Hz_16bit_30sec.mp3

For the full article http://www.thegearpage.net/board/index.php?threads/scope-died-anyone-use-the-pc-based-ones.1620645/

In your case and considering expected speaker levels I recommend 100k:1k attenuator if you feed the PC soundcard Line in and 100k/100 ohms if you feed the (not recommended) microphone in.

There is always the possibility of a failing Voice coil in the speaker/s which does sound like distortion
Run it into another speaker,, If no distortion into another speaker then you have a faulty speaker.
Phil.