Some experiments with bridging audio amplifiers
0Bridging a stereo amplifier in order to achieve a higher output power into a single speaker is fairly common practise, but information about how two bridged amplifiers perform when compared to themselves in a single-ended configuration is somewhat scarce. In this video I look at how three stereo amplifiers perform when bridged, and compare it to how they perform in their native, stereo configuration.
Note that I only used a very small sample size for this test. While my results show some trends, they're by no means conclusive or representative for amplifiers in general.
Notes on the test jig:
Signal was supplied by a computer equipped with an ASUS Xonar DX sound card. THD+N of the card is roughly 0,001 %. An ASIO-enabled signal generator was set up to put out a 1 kHz sine wave on both channels, with a 180 ° phase difference between the channels. This was a simpler and more reliable way of achieving BTL operation than for instance using an op-amp to invert the signal.
One channel of the stereo coupling box was connected to a single-ended output of the amplifier under test, whereas the other channel was connected between the two channels. An 8-Ohm load was connected to whichever outputs that were being tested.
Ground was lifted on the HP 339A distortion meter used for the test, the only ground came through the computer (which was disconnected during the noise tests).
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