[sdiy] decoupling caps again

[rsdio at sounds.wa.com]

When it comes to capacitor selection, there are at least a couple of  
important distinctions.

1) Many people obsess about the type and quality of a capacitor that  
is in the audio path, sometimes spending way more money on some  
esoteric capacitor just for its sound. In this context, decoupling  
caps are not important in the sense that the audio that you hear does  
not pass through a decoupling cap.

2) The article you listed is showing why decoupling capacitors are  
necessary. I don't think anybody is saying that they are not  
necessary. But it's a totally different statement to say that you  
don't need to care about the audio qualities of a decoupling cap.  
Also, the type and quality of a decoupling cap is important in  
different ways, because it is performing a different function than an  
audio cap. As you can see in the article, the physical arrangement of  
the PCB, the size of the traces, and the order the signals pass  
through the decoupling caps all have importance. But basically none  
of that is the same as what someone might spend a lot of money on for  
an audio cap. To put it another way, decoupling is absolutely  
necessary, but paying for high-grade audio caps is not at all  
important for decoupling.

Brian Willoughby
Sound Consulting


On Sep 2, 2013, at 12:25, Ingo Debus wrote:
> in the past, we often discussed decoupling caps. Several people  
> said, in audio circuit these are not that important, since there  
> are only fairly low frequencies involved. Have a look at this:
>
> <http://e2e.ti.com/blogs_/b/precisiondesignshub/archive/2013/08/13/ 
> the-decoupling-capacitor-is-it-really-necessary.aspx? 
> HQS=hpa_prechubdecoup_130901&DCMP=mytinwsltr_08_31_2013&sp_rid_pod3=LT 
> IyNjA0OTg5MDgS1&sp_mid_pod3=4968551>
>
> Ingo