I've recently changed my Line6 HD500 to a HD PRO. 
There is little differences, but I wanted a rack unit so when I got the chance to swap them for a difference of about 50$ i went for it. 
 
one of the things the HD pro has, is AES/EBU output. 
(as I understand, this it 24bit digital out?) 
How can I take advantage of this with my Tascam FW1884? 
AFAIK, the FW1884 do not have AES/EBU in. But it does have ADAT, could I get a ADAT preamp with AES/EBU input? 
 
 
Please bear in mind, I have no clue of ADAT, AES/EBU and similar topics :)

Or - would there be the same as using the SPDIF out? 

AES/EBU (now referred to as AES) is a more feature rich, and balanced version of S/P-DIF. There are a number of articles on the web that describe inexpensive ways to convert from one to the other. Most of them probably work.
 
A few minor points:

• AES is available on copper only (well mostly, you can convert copper to fiber and back.) It supports 2 channels, with no real limits on word length or sample rate. It uses a balanced interface. It includes a bunch of status bits that can make life easier for software and hardware developers. It is also the basis of a LOT of other digital audio formats.

• S/P-DIF is available on copper or optical fiber. It supports 2 channels, and I don't think there is a practical limit to either word length or sample rate, but there might be. It uses a single ended interface.

• ADAT is available on optical fiber only. ADAT supports 8 channels, with word length up to 24 bits, and sample rates up to 48 kHz.

OK, so since my FW1884 does not have AES input I'll have to convert from AES to ADAT. 
It will probably be more expensive than my gain from SPDIF to AES? :)

kristoffer
OK, so since my FW1884 does not have AES input I'll have to convert from AES to ADAT. 
It will probably be more expensive than my gain from SPDIF to AES? :)

I do apologize, but I think I am confused... and I am pretty sure you don't want to convert from ADAT to AES, but I'm not positive, so let's quickly review...
 
Your Tascam FW-1884 has two optical ports that can be used for either ADAT Lightpipe (8 channels, up to 24 bit wordlength, up to 48 kHz sample rate) and two coaxial (RCA Style) ports for S/P-DIF.
 
Your new POD HD Pro (and I am a little envious, I have a POD XT Pro) has both AES/EBU inputs and outputs on an XLR connectors, and S/P-DIF inputs and outputs on coaxial connectors.
 
If that's the case, then your best bet is to connect the coaxial I/O on the POD to the coaxial I/O on the FW-1884.
 
There is no advantage to converting to ADAT, nor is there any advantage to converting to optical S/P-DIF. And while you could convert AES to S/P-DIF with little or no penalty, there is no advantage to that either.
 
If you are already using the S/P-DIF coaxial connectors on the FW-1884 for some other device then that does make things a little more complicated. In which case, I'd convert the AES signal on the POD to S/P-DIF.
 
Does that make sense?
 
If you'd like a little more information about AES and S/P-DIF then check out this little application note from our friends at Frontier Design Group. Barry says it better than I ever could!

Makes sense :) That was just what I'm after: (my question was a bit unclear, as English is not my native Language) do I have anything to gain from using AES instead of SPDIF. As you say. No :)

Your English was just fine! And I think you've found your solution. Now I need to justify upgrading from the Pod Pro to the Pod HD<G>...

Yes, I'll probably found the solution :)
I actually had the HD500 until recently, so when I got the chance to swap it With a Pro With just 30$ between I went for it.
(I also had FBV lying around, toghether With a POD XT and a POD X3)
 
If you have the floorspace for it, the HD500 is just fine. I send the dry signal out the SPDIF.