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PA100 GC - 100W per channel, 2x LM3886 in parallel power amplifier




The 20k and 1k resistors are hand matched to 0.1%. For the output resistors, I used six 0.5W 1% 1ohm resistors in parallel per 3886 output instead of one 3W resistor because 3W 1% resistors are hard to find.

 

I used the insulated version - LM3886 TF, so that I can mount it directly to the case and heat sink with thermal compound.

 

Coupling capacitor is Auricap 1uF 450V. I used this high quality capacitor because it is in the main signal path.

The HF filter capacitors are Silver Mica 47pF and 220pF.

 

The power supply filter used is Blackgate 1000uF 50V.

 

C2 and C6 are Blackgate 100uF 50V. For better result, the bi-polar version should be used. However I am not using it because the bi-polar blackgate is too big to fit into my PCB.

 

The 680 ohm + 470pF filter network is installed at the RCA. This help filtering the high frequency noise before it gets onto the board.

The WIMA 0.1uF supply decoupling capacitors are soldered directly on the pins of LM3886 at the back of the PCB. This helped to remove some high frequency noise.

The 3886 are mounted on a 3/8 inch aluminum plate then to the case. Outside of the case I used 3 PC CPU heatsinks. I used Arctic Silver thermal compound between the aluminum layers to improve heat conductivity.

With all these big heatsinks, it only get slightly warm when listen at normal volume.

 

 

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