[time-nuts] Two V(in)s walk into a bar...

Azelio Boriani azelio.boriani at gmail.com
Thu Jun 25 13:19:35 UTC 2015

>From a 2012 discussion on time-nuts by M. Simon and Voker Esper:


There are 3 parts to the article - links are available at the end of
every section to the next section.

On Wed, Jun 24, 2015 at 11:54 PM, Neil Schroeder <gigneil at gmail.com> wrote:
> Lets take a hypothetical device, like specifically a PRS10, but could be
> any time/freq device like a PLL or an amplifier or all of these.
> Isolating power supplies with some dexterity can greatly improve noise
> control, and less peformance related, can help us protect very very
> expensive circuits from their less bourgeois support ICs.  Many of us may
> choose to implement them as modular devices for easy relocation or
> replacement.
> Main question: if I want to isolate the quiet and noisy power supplies, or
> just supply them differently, can they share a common return?
> The basic answer has to be yes.  Eventually everything has to get back to
> ground, and the Earth itself is a fair equalizer of all things on it.  I
> can clearly join analog and digital back at the input supply.  But if I had
> them isolated, do those iso grounds have to stay with their iso supplies?
> Take the PRS10 - it has two cables for Vin - power and signal supplies -
> but only one return cable.  Can i isolate, via transformers couplers what
> have you the two supplies yet return the common ground to one or the other?
> The signals handle themselves - they each have a ground wire of their own,
> or does that handle it ?  Are each of those opportunities for a loop?
> I know it'd work with just keeping separate DVcc and AVcc supplies that
> join at some point, and then that return can join at the star ground like
> everyone else.  If you are designing the module, you can handle the
> isolation inside and just have one input supply and return then isolate new
> supplies internally and eliminate the second cable.  Or two in vcc, two out
> gnd.  Those all make sense.
>  I think the single return option on the PRS10 is what's hanging me up
> here.
> Does isolation offer any real further benefit than AVxx and DVxx that is
> even worth pursuing outside the extreme use cases?
> Lots of words.  Thanks.
> NS
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