I was just looking at PA100 DIY 2x LM3886 in parallel gainclone audio amplifier and noticed that he uses 3 x 0.5ohm (1W) resistors in parallel on the output of each LM3886 in his parallel configuration. This ends up 0.1666 ohms (3W). He is using 30 volts and 4 ohm load. So does this mean he is dropping (.166 / 4.166) x 30 = 1.19 volts across the resistor pack, and also power dissipated in the resistors, (1.19 x 1.19) x 0.166 = 0.2 Watt.
On his BPA300 watt design, he uses single 0.2ohm 2 watt resistors on the output. How closely matched do these resistors have to be?
Also, on the feedback loop of each amp, the resistors have to be very close also, but what happens if they are not? I assume the dc offset is affected.
On his BPA300 watt design, he uses single 0.2ohm 2 watt resistors on the output. How closely matched do these resistors have to be?
Also, on the feedback loop of each amp, the resistors have to be very close also, but what happens if they are not? I assume the dc offset is affected.
Since you will never be able to match the amps 100 % it is necessary to put a ressitor in series to each chip amp's output and create the summed output of the parallel amplifier after those resistors. Those are the load sharing resistors, because they ensure that the load is more equally shared among the amps.
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