NortuRE Blog

Well, it’s actually an additional pair of LM3886T chip amplifier, which I ordered  again through a local supplier for the same amount of money (IDR 150000 or US$16.70). I previously have made 4 marking for drill holes because I intended to make two pairs of amps, but since I’ve only got a pair, I drilled two holes first for the mounting of the ICs in the middle of the heatsink. So basically I just have to add two more drillholes and that’s it.

The previous and added pairs are configured for bridge mode operation into 6Ω speakers for 2 channels. This was simply achieved using just one 100kΩ resistor from one of the LM3886 output pin to the other’s inverting input pin. As usual, more info on bridging amplifiers can be found in the Wikipedia.

Oh, by the way I’ve also modded the PSU that powers the amp too! I replaced the 2200μF 35V caps on the filtering side to a pair of 6800μF 50V ones because those smaller caps bulged! This is becoming an obnoxious issue nowadays. Many blogs and articles made mention of bulging capacitors countless times, mainly because of bad manufacturing practice. Heck even Wikipedia has an entry about it too.

One incident happened though, after I replaced the caps. In the above image one of the IRFZ44N mosfets is missing, it blew up! The incident happened just after I increased the amp volume to about 60%. I think the current transient and its associated heat are exacerbating the positive temperature coefficient characteristic of the MOSFET.