[sdiy] dirty/clean ground again

[Batz Goodfortune]

Y-ellow Roman 'n' all.

At 09:50 AM 8/17/02 +0200, Roman wrote:

>all decouple opamps with dual caps to ground. Isn't it more justified to use
>single cap just across power rails? The current spikes are there only, leaving
>ground as reference voltage. With CMRR and PSRR high enough it should have no
>impact on signal even if power rails travels with respect to ground in
>semi-uncontrolled manner.

In fact I've done this for years. Paraphrasing Ken, Unless there's an 
imperative to do otherwise, there's little point and it's a whole lot more 
convenient physically too. But there's one other thing I've always done 
which I was surprised to lean wasn't entirely heard of in these here parts, 
and that is to use about 100 ohms into the op-amp from each power rail. 
Effectively forming a sodding great filter around each device. Nothing gets 
in, nothing gets out. This doesn't work for everything of course. CV stuff 
might have it's own peculiar needs but for most audio systems it's like 
putting nice big suspension springs on your device for a real smooth ride.

I've never thought about the pot angle before but perhaps that's because 
I've never noticed any real problem with any of this before. Some of my 
earlier, large mixer designs had regulators on each channel strip. It all 
amounts to the same sort of thing. Smooooooth.

In fact, I'm not sure without checking and I really don't wanna have to do 
that right now, but I'm pretty sure there's a more detailed description of 
all of this in the NSC audio handbook. An absolutely mandatory compendium IMHO.

So just to put you straight. Yes Roman, you are nuts but not for this reason.

Hope this helps.

Be absolutely Icebox.

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