[sdiy] Audio decoupling caps

[Neil Johnson]

Hi Tom,

> What're your favourite caps for audio decoupling applications?

It depends.  What cut-off frequency do you want?  What are your
circuit impedances?  And how fussy are you about distortion?

At low impedances or low cutoff frequencies (say, a few Hz) I go with
electrolytic.  On inputs use bipolar electrolytics, or back-to-back
polarised (+ outwards) and bias the mid-point to -ve rail via a meg or
two.  If you're feeling very audiophilic then parallel with a film
capacitor.  Similarly for outputs.  Internally a single electrolytic,
and check which direction any DC bias will go and arrange the polarity
accordingly.  Or work with the bias (beware pots and switches!) and
avoid caps where possible (low offset op-amps help).

Neil
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