Build Power Amplifier LM4780 with BPA-200 Amplifier

This is design is very similar to the National Semiconductor BPA-200 (Bridge/Parallel Amplifier) which uses 4x LM3886 per channel and an input buffer:

Nothing Special in design but usefully for more watts!

My one will use 2x BrianGT LM4780 kits and a balanced line driver to bridge them, like this:


The LM4780 is a stereo audio amplifier capable of typically delivering 60W per channel of continuous average output power into an 8 load with less than 0.5% THD+N from 20Hz - 20kHz.

The LM4780 is fully protected utilizing National's Self Peak Instantaneous Temperature (°Ke) (SPiKeTM) protection circuitry. SPiKe provides a dynamically optimized Safe Operating Area (SOA). SPiKe protection completely safeguards the LM4780's outputs against over-voltage, under-voltage, overloads, shorts to the supplies or GND, thermal runaway and instantaneous temperature peaks. The advanced protection features of the LM4780 places it in a class above discrete and hybrid amplifiers.

Each amplifier of the LM4780 has an independent smooth transition fade-in/out mute.

The LM4780 can easily be configured for bridge or parallel operation for 120W mono solutions.

The total effect is (2x LM3886's paralleled) x2 Bridged and should give approx 225 watts into 8 ohm and 335 watts into 4 ohm when used with a sufficient power supply.

The line driver part is based on the DRV134 and a PCB from digi01, you can see the details here.

In the end mine was dual mono in a recycled amp case using 2x 300VA (18VACx2) toroidal transformers, 54,400uF of capacitance per channel with a snubber. The DRV134s add 6dB of gain so I set the LM4780s to about 16x gain to compensate (they are set to 33 normally). I get no DC offset, no hum, no crackle or thump on turn on or turn off, silent as.


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