Cathode bias caps

My DIY PSET 300B monoblocks currently use electrolytics to shunt AC in the cathode bias circuits (both for the driver and 300Bs). Has anyone tried using film caps, or bypassing the electrolytics with film caps? If so, what did this do to the sound quality?


The correct term is 'cathode bypass' capacitor.

The capacitor is biased with a voltage larger than any audio signal it might pass. As a result, its distortion is quite low- rivaling film caps with no problem at all.

The reason electrolytic caps are reviled for coupling capacitors is because they have been mis-applied. For them to work properly, they must have enough DC voltage on them that the audio they are passing will not come anywhere near that DC voltage. In this way they will pass the audio signal quite well.