AC Coupling Capacitors

Discussion in 'General Electronics Chat' started by Skeebopstop, Jan 7, 2010.

  1. Skeebopstop

    Thread Starter Active Member

    Jan 9, 2009
    Hi All,

    I've recently designed an audio amplifier and used low esr tantalum caps for ac coupling at the input stage. I checked against an international rectifier design and they do the same thing, except they use general purpose tants and not low esr.

    I read a white paper showing that ac coupling with low esr tantalums, in particular NiOb, provides minimal THD and compares adequately to other really expensive types. I am unsure if the setup for the white paper was using a Class A amplifier for test or not.

    I guess what I find a bit odd in doing this is that they are 'polarized' caps coupling an ac signal which in some situaitons may not be DC biased and thus have a negative component.

    Originally I was using multilayer chip capacitors but after some reading found out they can introduce a fair amount of distortion so I changed. The tantalums are working great from 3 different pre-amp sources (I'm assuming 3 differing pre-amps from 3 differing applications, all of modern devices, won't be using class A biasing).

    Any comments? All my reading thus far has only really provided cautionary measures when using electrolytic but said little about tantalum. I have seen some forums where people mention audio equipment companies sometimes use aluminum electrolytics (perhaps they designed a class A preamp stage though).