The "instant amp project"... ;)

[sfx]

Hi everyone,

can't resist to post some pictures of my latest creation. I was annoyed because my class D subwoofer amp burnt beyond repair, and the sub was sitting in my room, not doing anything. So I needed an amplifier, quick!

I got an STK086 (80 Watt RMS into 4 Ohm), and a transformer, some components, etc - about A$100 altogether. The case once was a car 240V inverter, the heatsink is an old CPU heatsink.
The whole thing took my two afternoons. The STK is not the greatest amp in the world, but it's good enough for my subwoofer. I was afraid 80 Watts RMS might not be enough (it's an electronically compensated sealed box, so power demands go up for low frequencies) - but hey, it doesn't clip even at groundshaking volumes, and drives the speaker up to 7-8 mm into excursion without significant distortion. I'm quite surprised For full-range speakers, it's ok for lower volumes, when nothing else is at hand, but THD goes up a bit at full power... But since my subwoofer is only responsible for everything below 60Hz, it does the job just fine - for now

pictures

[EsotericTT]

I have been trying to repair my M&K V-2B subwoofer. It employes the same power amp chip. One day, the thing just died. So, I replaced he chip and brought it back to life. To my surprise the sub now has a curious THD problem.

Viewed on a scope, one can easily see a little glitch of high frequency oscillation at or near the zero crossing of sine waves. It sounds like a "buzz" accompanying sustained low frequency sounds. I have just about checked or replaced every single part on the PCB. Still it persists. Did you experience any similar problems?