[PlanetCCRMA] multiple card synching

Mark Knecht Mark Knecht <markknecht@gmail.com>
Thu Feb 24 06:34:01 2005

On Thu, 24 Feb 2005 15:01:42 +0100, Michele Spinolo
<michele.spinolo@tin.it> wrote:
> Hi Mark,
> thank you for your reply!
> > 1) On your remote source with 3 spdif outputs are you completely sure
> > that they are in sync with each other when transmitting? It would seem
> > like a reasonable assumuption but it may not be true. Check the specs
> > on that device very carefully. Read forums, etc. for that device (what
> > is it?) and see if others have had similar results. (good or bad)
> I will contact the builder of this stuff, FYI this is the board I am
> speaking of:
> http://www.dvdupgrades.ch/150019/Modification/SPDIF/Output/Six_channel_S_P_DIF_output_board.html

An interesting device! 

> in negative case do you know of such a device who could sync my 3 s/pdif
> signals?

Take the following with a grain of salt...

I spotted this text: "In the DVD player you will find a clock line and
a data line for every channel pair. Each clock cycle means one bit of
audio data." When I first looked at the picture I thought there might
only be one clock since there's only one Actel FPGA. However there are
three cables driving this chip. (The rainbow cables.) It seems likely
to me that each cable carries it's own clock and the Actel chip is
operating on each on independently. If true (and I'm only guessing
about that) then each channel would be independent and unsynced.

> > 2) Doing the soldering routine sould be the last thing you do. I would
> > think that if the card has the cabaility of being synced via software
> > then the developer for that driver should be contacted. On the RME
> > HDSP cards we have an application that gives us this capabiltiy. Talk
> > to the driver developer and see what you need to do to get him to
> > build this capabilitiy.
> I already tried to contact the ALSA's driver developer, but he seems not
> interested in developing such a capability.

That's disappointing but it may not be his fault. Some of the card
manufacturers do not want to release full specs and some fo these
features are only available if you have full specs. (Or are willing to
use a PCI bus analyzer in a Windows box to find out what's going

> Could you please suggest a RME HDSP card (as cheap as possible :-P ) which
> could work for my setup?

RME and 'cheap' don't go together very well. The low end HDSP 9652 is
still about $600 each and it has three ADAT interfaces you wouldn't be
using. That's not the right solution.

Actually it may not require an HDSP which is expensive and way more
card than you want. Possibly one of the smaller RME cards would work
using some sort of control language. Also, there are many well
supported 2 or 4 channel cards that have spdif inputs. Possibly one of
them would work? I have an AP2496 but I've never investigated whether
it can sync to spdif. If it did then 3 of them would be only
moderately painful I think.

> Thank you very much!

You are very welcome.

- Mark