S/P-DIF Continued:
Once you have all your clocking issues dealt with, then use S/P-DIF in the same way you would Analog In or Analog Out.
The most direct way is to drag the S/P-DIF In and S/P-DIF Out icons from the Hardware I/Os section of the menu onto the surface of the CreamWare sfp RoutingWindow. This provides a two channel (typically stereo) input from, and a two channel output to some digital device located outside the computer box.
An Example:
Let's say you want to listen to the digital output of a Tascam DA 30 Mk II DAT recorder. That model DAT machine has both S/P-DIF and AES/EBU inputs and outputs. If you have both a Scope or Pulsar Classic card and a Scope or Pulsar Plus card in your computer, you could connect using either S/P-DIF or AES/EBU. Which? I'd say use the one for which you have the better cable.
Please be aware that expensive digital cables do exist and not all of them are snake-oil. Still, I'd hesitate before spending thousands (or even hundreds) on a digital cable. At least make sure that you are using a digital - as opposed to audio, mic' or line - cable. (If you want to get technical, the difference between digital and audio cables has to do with impedance, and here it's a sort of 'sideways' measurement. Not at all like a simple resistance measured from one end to the other wherein a 1000 meter cable would have more resistance than a 1 meter cable of the same gauge. A search engine can provide more answers for the curious.)
If you insist, you could listen and try to pick whether AES/EBU or S/P-DIF sounds best. Good luck trying to hear a difference, though. A primary reason for using any digital connector is to assure that the signal is passed along without any alteration. So S/P-DIF, AES/EBU, ADAT lightpipe over a few feet should all sound exactly the same - in theory. For this example we'll stick with S/P-DIF.
info added 2/28/04
I'd like to thank Tom (known on PlanetZ as Astroman) for pointing out a 'fly' in the ointment of digital perfection. The error correction applied in a CD player for example, is not as robust as the error correction applied in a computer to a file. If you need to get as close to the original as possible, then a grabber program (e.g. cdparanoia) to convert the CDDA file to a .wav file is the way to go. Then, you probably wouldn't be using S/P-DIF, instead you'd just use your computer's data CD reader.
One other thing: it is not always a bad thing to go through a digital to analog/analog to digital cycle. In fact the conversion hardware may add or subtract just enough to give you the sound you are looking for - in a mix, for example. Conversion may be (in fact, has to be) less faithful than pure digital, but a little color can be useful now and then. For now, we'll persevere with the S/P-DIF, though.
Once you've made the physical connection between the DAT machine's S/P-DIF output and the CreamWare's Digital In, turn on the DAT machine. Load the DAT tape you want to hear and hit Play on the DAT machine. When you hit Play, an already recorded DAT tape will transmit its clock rate to the DAT machine. You should be able to tell the clock rate on the DAT by seeing either 44.1 or 48k on the DAT machine's display. Once the DAT's clock is displayed, you should be able to rewind the tape and hit Pause. The clock info should still be there. (A CD player gets its clock information from a valid CD and except for the parts about loading the DAT tape _ use a CD instead _ and 48k _CDs only do 44.1, the above information is also applicable.)
Start the CreamWare sfp environment, and adjust the SampleRate (under Set) so that CreamWare is a slave to the appropriate S/P-DIF input stream. Then just connect the output pads of the S/P-DIF In icon to a couple of channels on your VDAT or STM-2448 or what-have-you.
An Alias:
Scope and Pulsar (II) Plus users with AES/EBU digital connectors will still use the S/P-DIF icons (at least as of sfp 3.1c) since there is not a dedicated AES/EBU input or output icon. There is a workaround if you think this could cause a problem, say you have a clueless, yet stubborn, techno-snob client who might think the AES/EBU signal path was somehow polluted by having even the label "S/P-DIF" in the path. You can create your own AES/EBU-labeled icon. (This has more practical applications, too. So read on.)
Perhaps you say, "I have so many things connected to my CreamWare environment, the back of my computer looks like a porcupine at the beauty parlor. How can I possibly remember what goes where?"
Not to worry. CreamWare has the Tools to solve your problem. In fact, the Tools menu is where the "Source S" icon is found. For our DAT example, we will drag the Source S icon onto the CreamWare RoutingSurface and double click to open the icon's surface.
The first thing to do is to change the icon's name from "Source S" (which stands for Source Stereo) to something more meaningful, perhaps "DAT Play." It's as easy as changing any other text field in CreamWareLand, but this one actually displays as the name on the icon.
Below the name you will see two fields to the right of some potentially confusing labeling: Output then Left and Right. "But aren't we working with inputs?" you ask. Yes, but only into the DAT Play (formerly known as Source S) device. The output of the DAT Play icon is the stream it gets from the hardware (S/P-DIF) Input which in turn becomes ... well, the good thing is, you can't mess it up. When you click in the Left or Right field with the Right Mouse Button, a list of Sources is displayed. Choose an unused S/P-DIF Source then choose L Out. Repeat for the Right channel. Then you are almost done.
I recommend setting-up a separate directory for the icons you create using Source M, Source S, Destination M and Destination S tools (as well as the similar but more complex External Effects of various flavors under Effects/Stereo (or Mono)/Others). Then, you can save your new icon (using the save sub-icon on the device's upper-right-corner) so you don't have to do it all over again the next time.
There is one "gotcha" lurking behind these alias icons: the icon for the hardware I/O you want to connect must be physically present on the CreamWare RoutingSurface. I like to hide the physical icon below the bottom of the screen, because it does not have to be connected to anything. The connection is made with the alias icon.
Oh, and sometimes the alias icon dialogue may show that a physical connection is "occupied." The best way to deal with that is to experiment. A hint, before you experiment with stealing connections for alias icons, make sure that you can see the connections that are "occupied" then watch what happens
What We've Done:
Let's review. You decided that you want to use the S/P-DIF Out of a DAT player. You made a physical connection from the DAT player to your CreamWare card's Digital In and you made sure to use digital cable. You started playing the DAT tape so that it would furnish the clock.
On the CreamWare RoutingSurface (or using your favorite method) you connected the right-facing pads of the S/P-DIF source icon to two left-facing audio pads of some other icon. You made sure that CreamWare was slave to the appropriate S/P-DIF stream using the SampleRate dialogue. You set the levels in software, knowing that the DAT player's output levels have no control over the S/P-DIF stream. If you were comfortable with the idea of S/P-DIF, perhaps you set-up an alias icon. Now what are you waiting for? You're in CreamWareLand: make some music!
A Messy Post Script:
At some point, you may want to use an external device with S/P-DIF In and S/P-DIF Out. "Nifty," you think, "Now that device can stay entirely in the digital realm." Perhaps. The reason it gets messy is that sometimes it works, sometimes it doesn't. In general, later generation devices (CreamWare and external) tend to be more cooperative. And strict compliance to S/P-DIF standards may make a highly compliant device appear to be less capable than a more loosely-spec'ed device. Experimentation done at your leisure is the answer. A live show (or with an anxious client breathing down your neck) is not where you want to experiment with double (or even single) sided S/P-DIF.
Watch the Clock (or, Messy Post Script Part II):
A single active S/P-DIF stream appears to provide a stable clock to the CreamWare environment. Why not let CreamWare default to be slave to a DAT or CD player? Here's why not (in case you missed it above): the S/P-DIF clock that you might think of as coming from the DAT player or CD player is actually coming from the DAT tape or CD disc. If you don't have a DAT tape or a CD loaded, then you don't have clock.
john
<font size=-1>[ This Message was edited by: jabney on 2004-02-28 14:00 ]</font>
<font size=-1>[ This Message was edited by: jabney on 2004-02-28 18:57 ]</font>
<font size=-1>[ This Message was edited by: jabney on 2004-03-01 19:28 ]</font>
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