Although active load has much higher PSRR (Power Supply Rejection Ratio) or PS/tube isolation then passive (resistive) load, you can add additional filter stage(s). We have SS/tube diode bridge, then LC filter - simply add one LC filter for the right channel, and other LC filter for the left. You can use a small choke (say, "Hammond" 153E - 7H/25mA/770Ohms) and another "motor run" cap.