Amplifying bass frequencies

spec said:

I am sure the LM1875 will sound fine, but I don not like bridge amplifiers as they introduce more distortion and can get into a tangle with some music and difficult-to-drive speakers. There are much better integrated amplifiers.

To get the best from an amplifier you need direct coupling, which means plus and minus supply lines, and good components: metal film resistors and polypropylene capacitors or good quality aluminum electrolytic capacitors for the high values.

spec

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audioguru said:

I think your power supply filter capacitor is too small and/or the power supply voltage has series resistance causing its voltage to jump down when loaded then go back up when unloaded. Since the amplifier is non-inverting then the power supply fluctuations causes positive feedback and oscillation. Try increasing the value of the 10uF capacitor to 22μF or 33μF that is filtering the bias voltage.
Maybe the 19V is also powering the input signal source? Try disconnecting the input signal from the amplifier and report back if the bur bur sounds stop.

You said your power supply voltage is 19V. Then the LM1875 output power is only 3.5W when it begins clipping.

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