Trafomatic Audio's Classic 500 power conditioner uses narrow-band transformer coupling from a custom 800VA toroid to filter out unwanted AC line harmonics.

At 250Hz, attenuation already is 10dB, at ultrasonic frequencies in the 100kHz band, it is a very significant 45dB.

The Classic 500 offers outlets for three components. Classic 1000 and Classic 3000 are also available.