Split ADAT Optical Signal?

Discussion in 'Converters / Interfaces' started by jethro, Oct 26, 2003.

  1. jethro

    jethro Guest

    I'm trying to find a device that would split an 8 channel lightpipe signal into 2. I have an 8-channel preamp with 24-bit/44.1khz ADAT Lightpipe output.

    I need to send a signal to my computer for recording and also to my digital mixer for monitoring. I just need a simple 2-way splitter, but it needs to not affect the signal in any way.

    Anyone know of anything?? I found a HOSA ODY-314(?) that I get mixed reports on whether it's for 2-channel or 8-channel signals. Even HOSA gave me 2 different opinions on it.

    I just need something simple. Does it exist???

  2. theom

    theom Guest

    they do exist, they look like a dongle, 3 female optical connectors molded into a chunk or plastic.

    Do a google search for "fiber optic splitter adaptor"
    they are about $5-$15

    It might work, might not, but for $15 it's worth trying.
    Some clocking can deal with it some cant, you will only know if you try it with your rig.
    parts express has em for $6
    I think Part Number 180-964
    look for:
    Dayton Audio Optical Splitter
    bi-tronics sells them too.

    here's one
  3. AudioGaff

    AudioGaff Well-Known Member

    Feb 23, 2001
    Silicon Valley
    The ADAT optical protocol is not meant to be split. It is a dedicated 8-ch format. There are a devices that allow you mix ADAT optical so that the gain is equal to digital off (like more than -90 dbFS) most of these are bigger digital mixers, but I thought Hosa made a portable version.

    There is S/MUX or what is often called bit-splitters that will allow 1 channel of 24-bit up to 96kHz to be stored on two channels on a 16-bit ADAT machine. Rane used to make something called the paqrat and I think RME makes something that does this. Look for products that support S/MUX.

    Seems to me what you really need if anything is a digital patchbay with ADAT optical. Don't look for something to split the 8-channels, just use as many of them as you need and don't worry about the others.

    Why can't you just send the preamp ADAT output to the ADAT digital mixer input then from the digital mixer into you computer? Monitor through the mixer. That is the common way to do it.
  4. jethro

    jethro Guest

    Hmmm, thanks for the replies.

    I can't go through my mixer beacause it doesn't send the ADAT input directly out the ADAT output. It sends the analog input to the ADAT output. Also, it's an older 20-bit machine. I wanted to keep the signal pristine.

    So it looks like it's not really technically possible. Is this the case? That might be why it's been hard to find this kind of device.

    Any other ideas??
  5. AudioGaff

    AudioGaff Well-Known Member

    Feb 23, 2001
    Silicon Valley
    Why can't you send the preamp analog outputs into the analog inputs of the mixer and send the ADAT optical to the computer? Monitor through the mixer.

    20 or 24 bit has little to do with what makes a sound pristine or not. You do know that at any time that 24-signal goes through that mixer, you will lose any benifit from the extra 4-bits that you seem concerned about.

    If your looking for specific suggestions, then list all your gear (make and model) and all your connections, as well as what your trying to do and any limitations trying to do it. Then we can go from there.
  6. jethro

    jethro Guest


    I have a PreSonus Digimax LT mic preamp. It has 8 channels with ADAT Lightpipe output. It works at 24-bit/48khz.

    I have an RME Hammerfall 9652 audio card in my computer which accepts the Lightpipe in and Word clock.

    I have a Fostex VM200 mixer for monitoring. It has 8 channels analog and 8 channels digital (using Lightpipe in/out). It is older, with 20 bit converters. It passes the 8 analog input channels directly out to the corresponding ADAT Lightpipe channels.

    I bought the Digimax specifically to give me a good, clean input path for recording. The Fostex I've just had for a while and it works great for monitoring. When I'm not recording, I use the Digimax to add an additional 8 analog input channels to my mixer (other instruments, etc.) I would love to not have to switch them around every time I wanted to record.

    I'm also concerned about sync. In the past, I've encountered some clicks/pops. It may have happened when using the mixer. The Digimax seems to do pretty good.

    Thanks again!
  7. AudioGaff

    AudioGaff Well-Known Member

    Feb 23, 2001
    Silicon Valley
    A few more questions.

    What gets connected to the analog inputs of the mixer?

    Is the ADAT optical in the digital mixer 24-bit?

    Is the digital mixer 98kHz capable?

    What does the mixer have wordclock in and out?
  8. Kurt Foster

    Kurt Foster Distinguished Member

    Jul 2, 2002
    77 Sunset Lane.
    Does your mic pre have analog outputs? Send those to the analong inputs of the mixer and send the lightpipe to the recorder.
  9. jethro

    jethro Guest

    Thanks guys for the help!

    The preamp has inserts on each channel. If I insert a 1/4" cable half way in, it can work like an analog output. I could work this way.

    But for when I'm not recording, I have all 8 analog inputs on my mixer used for other things. And then I use the preamp to send up to 8 more signals to the ADAT in on the mixer. It's just really nice to not have to switch things around all the time when I just want to play around without firing up the computer.

    I guess I'll just have to live with switching stuff when it's time to record. Oh well...
  10. MisterBlue

    MisterBlue Member

    Mar 15, 2003
    I think this is the gadget that you are looking for. Theom already referred to it:


    It's a pretty trivial concept in that it really only splits a light beam into two. As it is digital it will be just fine as long as it doesn't get attenuated too much (which shouldn't be the case with these devices).

  11. theom

    theom Guest

    In your case the spiltter should work.

    For such little money, It is worth a try.

    I use one out of my B rig. My digi 001 optical out goes into the splitter then into my 8 ch d/a and the other side of the split goes to my eventide eclipse.

    It works fine.
  12. FloodStage

    FloodStage Active Member

    Feb 23, 2003
    The inserts on the Digimax will do what you want. I send those inserts to my headphone amp when tracking.

    If you want to stay digital, get a good digital patchbays. Not all of them will do it, but mine will. Absolutely make sure that all channels have PLL clocking by the way. (Don't get the Fostex for instance)

    Here is the link (cost - about 600)
    Frontier Apache Digital Patch Bay
  13. jethro

    jethro Guest

    Thanks again for all the speedy replies! I really appreciate it.

    I did finally get the "official" answer from HOSA on their optical splitter. It turns out that the ODY-314 was originally intended to split ADAT signals, but the internal card wasn't fast enough to handle the heavy data of an ADAT signal. So it's only good for 2 channel Toslink. That's where the confusion came in. Some packages leaked out stating it was compatible with ADAT.

    They do have a module that's part of their more high-end digital patchbay which has the faster card that can handle ADAT lightpipe. The tech told me that I could use the module on it's own without the chasis, it just might be a bit 'flimsy'. I may give this a try.

    The cheap optical splitter thing looks interesting, I just wonder about the integrity of the signal after hearing from HOSA and the other post that mentioned PLL, etc. If it was just for listening, it would probably be OK. But for recording, I don't want to hassle with the pops, clicks & other frustrations of a bad clock sync or jitter. I spent over 3 months trying to debug that kind of stuff on my other computer. That's why I bought the Digimax in the first place.
  14. MisterBlue

    MisterBlue Member

    Mar 15, 2003
    As it is optical there will not be any jitter introduced worth mentioning. The clock information is embedded in the signal and can't be corrupted easily by simply splitting the signal (unless the signal is weakened so much that it is no longer properly recognized - also not too likely IMHO).

    Pops and clicks in PC based audio workstations usually have other reasons than signal integrity but that's a whole different topic that has been discussed a million times on other threads.


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