[LAU] [OT reply to recived OT ; )] RME analog out of phase to ADAT connected Behringer analog out

Arnold Krille arnold at arnoldarts.de
Tue Jun 14 14:51:05 UTC 2011

On Tuesday 14 June 2011 16:03:35 Ralf Mardorf wrote:
> On Tue, 2011-06-14 at 08:22 -0400, Paul Davis wrote:
> > On Tue, Jun 14, 2011 at 8:11 AM, Ralf Mardorf
> > 
> > <ralf.mardorf at alice-dsl.net> wrote:
> > > And as you could read I found an issue. At Thomann (a German dealer)
> > > they claimed there are no sync issues, what I couldn't believe. Doing
> > > this test I found out, that there are bad phases.
> > 
> > You DIDN'T SYNC ANYTHING. Or at least, your description doesn't
> > mention any kind of sync.
> That might be correct. The optical ADAT connection can't be used for
> sync?
> > And if you had tried to sync, you would have
> > found that you CANNOT sync two A/D converters unless they are the
> > exact same model (so that their pre-A/D buffer is the same size).
> I suspect the RME using other, better converters than the Behringer
> does. This is why I expect that a completely perfect sync for the phases
> might be impossible. Thomann (the dealer) claimed I'm mistaken ;), sync
> is possible.
> Anyway, I'll read about ADAT and sync. ADAT is new for me, since in the
> earlier days it was used by semi-professional studios only, I never was
> in a professional studio or home recording studio using ADAT. I guess
> today it's more common than it was 'some' years ago.
> I thought ADAT is similar to S/PDIF and usually S/PDIF is used to sync
> identical elCheapo cards when using them as one virtual card, something
> I never tried to do with my Terratec cards, instead I bought the RME.

All ADAT (or any other word-clock) syncs is the sample-clock of the 
processing, it doesn't sync the times the converters need to output the sample 
as analog audio. And these times depend on the actual chip used. So you can't 
even expect one adat-io-converter from one manufacturer and another by the 
same manufacturer to be of the same "latency" because they might use different 
chips inside with different conversion latencies.

To have it exactly in sync, you have to use only one kind of converters in 
your setup.
Or live with the fact that one sample at 48kHz is only some centimeters of 
distance, and the conversion-latency is usually below that. So its probably 
okay for normal recording-, live- and playback-usage.

Have fun,

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