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.

Two pairs it is

Side view

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.

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Kali ini postingannya pake Bahasa Indonesia aja deh, soalnya sejak pertama kali direlaunching blog ini pake English melulu. Hehehe. Lanjut. Setelah saya mengobservasi beberapa PSU switching yang menggunakan IC PWM Controller TL494CN, dari kesemuanya (ya, benar, semuanya!) tidak ada satupun yang memanfaatkan fitur op-amp bawaan IC tersebut. Padahal op-amp itu bisa kita manfaatkan untuk mengatur/meregulasi tegangan keluaran power supply sehingga tetap stabil walaupun bebannya berubah-ubah. Anda yang kurang paham dengan regulasi, mungkin tahu dengan IC regulator 7805. Nah, prinsipnya sebenarnya sama, yaitu tegangan keluaran PSU diumpan-balikkan ke op-amp IC TL494CN. Op-amp ini akan membandingkan tegangan keluaran tersebut dengan tegangan referensi internal IC PWM sebesar 5V. Apabila melebihi atau malah kurang, lebar pulsa yang diumpan ke MOSFET akan disesuaikan sehingga tegangan keluaran PSU akan tetap stabil walaupun bebannya berubah-ubah.

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This is about my SMPS (Switch Mode Power Supply) for the gainclone amplifier I previously have posted. An SMPS differs to the conventional linear 50Hz power supply (pictured below) in that it converts mains voltage using a smaller HF transformer. This small size is made possible because the current is switched (or turned on and off) by a pair of switching transistors or MOSFETs at more than 40000 times a second (40 kHz) compared to the 50 times of the mentioned linear PSUs. Further information is available at Wikipedia here if you want to know more.

Mains Transformers, Left: EL-type, Right: Toroidal

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