Re: [AH] Doepfer Opinions (PSU CROSSTALK)

From Tomislav Babic
Sent Fri, Feb 8th 2008, 15:50

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hi Peter. thanks for the info on this, thats what i was getting at..

since i recall you being a frac user in the past, with those wonderful
babluma
and segway to part4 demos,   do u happen to know if this grounding scheme
is done differently/better  on Blacet/Frac systems, and for examples on MOTM
?

how about AS racks, or the upcoming 3-angled PlanB rack ?


PS i did start a frac system, but recent releases of more adventorous planB
and livewire
modules that interest me, has made me consider eurorack too..

thanks

On Feb 8, 2008 3:11 PM, Plan B (Peter Grenader) <peter@ear-group.net> wrote:

>
> On Feb 8, 2008, at 4:52 AM, Florian Anwander wrote:
>
> >> my main concern with Doepfer is quality, are there any issues with
> >> crosstalk
> >> or quality of rails n PSU?
> >> i remember reading somehjting about it, but have none personal
> >> experience.,,
> >
>
>
> > No. There is no "crosstalk",
>
>
> Um...with all respect, there most certainly is an issue with
> crosstalk with current Eurorack power busses. The ground connections
> on the bussboards are daisychained, which results in an open path for
> noise created by one module to be  transmitted down the line.  As a
> result, VCOs and some filters placed in the same rack (powered by the
> same PSU) as LFOs, EGs, and modules which use PICs or Microp's and
> others which are notorious noise makers will cause the zero
> transitions of these listed modules to be heard at the outputs audio
> modules which share the same power.  So by noise I don't mean white
> noise, but I so mean clicks, hums and audible LFO oscillations in the
> signal path. This effect can be lessened by connecting the power to
> any audio modules in shared racks as close to the main power inputs
> as possible.  This works in some instances.
>
> There should have had separate ground traces running from each of the
> connectors on the bussboard directly to it's power input terminals
> which lead to the PSU.
>
> There is a fix however if you've using racks in duplicates of two
> (meaning an even number of rack cases), but it'll cost you two more
> bussboards per pair:
>
> If you purchase an extra bussboard per rack, mount a second into each
> of the cases, then make separate cables coming from the two PSUs (one
> in one rack, one in the other) and interconnect them so that one PSU
> in one rack powers one bussboard in each of the two cases, and the
> PSU in the second case powers the others bussboard in each of the
> cases, then you've created separate power systems for audio modules
> and control modules.
>
> - P
>
>
>
> Peter Grenader
> e: peter@ear-group.net
> p: 888 791-0010
> w: http://www.ear-group.net
>
>
>
>


-- 
---
Tomislav Babic
www.babic.com - studio, mp3, info
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