Mic preamp -> S/PDIF -> Mbox2 = 4 mic inputs on Mbox2?

Discussion in 'Preamps / Channel Strips' started by lazyshark, Jan 16, 2006.

  1. lazyshark

    lazyshark Guest

    I don't know much about digital signals and stuff. I just realized my Mbox 2 has 4 inputs, the 2 mic preamps and a 2 channel S/PDIF thingy (?). Am I right? So, is there a piece of hardware that lets me hook up two microphones, and send the signal via S/PDIF to my Mbox 2, so I can record from four microphones at the same time to seperate channels?

  2. Kev

    Kev Well-Known Member

    Nov 13, 2001
    yes for M-Box 2
    (similar to AMIII card)

    A dual mic-pre with SPDF output
    a Line to SPDF unit and add 2 Mic to line amps
    Set M-box for external digital clock on the SPDF

    4 mics and record the 4 four sources in one pass

    example of Mic to SPDF

    example of Line to SPDF
  3. McCheese

    McCheese Well-Known Member

    Mar 24, 2005
    Um....no, last time I checked either it blended the two pairs of channels (i.e. Channel 1 Analog and Channel 1 SPDIF wrote to one track...) or the SPDIF overrides the analog altogether.

    In fact, I think you have to choose analog or SPDIF in the settings of PTLE.

    I don't have a SPDIF source to use to check this, but I know PTLE only recognizes two inputs from the MBox.

    From the digi site:

    "The USB spec only allows for a certain amount of Data to pass in either direction at any given time, and there is simply not enough bandwidth to handle the load presented by 4 discrete audio streams. Audiomedia III uses the PCI bus for throughput, which is not limited in this way."
  4. Kev

    Kev Well-Known Member

    Nov 13, 2001

    err ... SPDF is a 2 channel protocol just like AES EBU

    so you may see references like SPDF left & SPDF right
    SPDF 1 & SPDF 2

    I don't have an MB2 to test I can't know if the USB can handle the data rate.
    I think USB2 could handle a simple 4 channel 16bit 44.1k stream but not a 4 ch 24/96
    See the Rane technical library I'm sure I've said that a few times here

    I'm still searching for a likely Dual Ch Mic-pre with SPDF as the one I listed above was only a single

    How about a cheapy
    from the Focusrite range
    ISA4280 with digital card

    Digital output options include dual AES/EBU, SPDIF and dual ADAT lightpipe. Full digital metering is provided for every channel, alongside new 'moving coil' peak meters, designed to catch even the fastest of transients.

    then use two via SPDF and 2 via analog to the M-box line inputs.
    then record all at the old style 16/44.1 ... just for the effect

  5. McCheese

    McCheese Well-Known Member

    Mar 24, 2005
    Right, I know SPDIF is a 2 channel protocol. What I'm saying is that it either blends the 2 analog inputs and the 2 spdif inputs, giving you 1 track containing audio from both analog 1 and spdif 1, and another track containing audio from both analog 2 and spdif 2. OR you can only use one set at a time. I wish I had something to plug into my spdif to test it out.

    You can't run all 4 to seperate tracks.
  6. lazyshark

    lazyshark Guest

    I realized my computer has S/PDIF output, so I hooked my computer S/P out to the Mbox S/P in, played a sound file with VLC, hooked up a microphone to Input 1, a guitar fx processor which has a drum machine to DI on Input 2. Voila.. 4 seperate channels of recording at the same time @ 24-bit / 48 kHz. I soloed all the channels, and they only have their own sound, no blending. Now seeing as the S/PDIF signal came from my PC, and went back into my PC doesn't matter in this case right? The Mbox 2 just reads what it gets?

    The DigiTube looked nice, but I'd need two, and that's 500 bucks. I just can't seem to find a 2 mic preamp -> S/PDIF for cheap. Could I go, mic preamp -> line or something -> line to S/PDIF or something like that, as there are some cheap mic pres? And say I have two DigiTube's, they each have 1 SP out each. How do I hook that up to my 1 SP in so I get L/R channels in ProTools?
  7. McCheese

    McCheese Well-Known Member

    Mar 24, 2005
    Wow, they fixed it for the Mbox 2, awesome!
  8. Kev

    Kev Well-Known Member

    Nov 13, 2001
    nothing fixed

    I was doing 4 channel record on the AMIII when it was first released.
    the basic input assignments on PT haven't changed sionce PT4.0 ... perhaps even earlier.

    TRUE - the M-Box original doesn't have the facility of 4 digital ports to Hard Drive ... just 2
    so either SPDF or 2 X Analog to Digital.

    The 001 through to HD still uses the same language and methods.

    All you need to be wary of is where your audio clock is being derived from
    ... and that you flip between internal and external when necessary.
  9. lazyshark

    lazyshark Guest

    As I'm pretty much a n00b to all this recording stuff. Audio clock is what now? I figured I could just go with an M-Audio Audio Buddy, and then line in on my computer, back out through S/PDIF and to my Mbox 2. I saw one for $69 on ebay, which would make this a very cheap 2 mic input upgrade for my Mbox. On second thought, my soundcard on my PC is probably only 24-bit 44.1kHz. I have an Soundblaster Audigy 2 on an old computer, which is 24-bit 192kHz I think. So all I have to make sure is the bitdepth and samplerate match on the Audigy and in PT, and I'm good to go?
  10. Kev

    Kev Well-Known Member

    Nov 13, 2001
    What ??

    M-Audio Audio Buddy
    2-channel mic/instrument preamp
    XLR mic ins; 1/4” instrument ins; balanced 1/4” outs
    phantom power
    5Hz-50kHz frequency response
    it doesn't have SPDF
    I don't see the upgrade
    your M-Box has two Mic-pres that will be every bit as good as the above.

    back up a bit and start again ...
    what is wrong with the simple M-Box and Protools as it stands right now ??

    If you just want to add two extra inputs and two Mic-pres potentially better and tonally a little different to the standard M-Box-2 then this DBX unit may help
    dbx 386 Dual Vacuum Tube Preamp
    (Dead Link Removed)
    It's a 2-channel tube mic preamp with digital outs and the dbx Type IV conversion system. It features selectable 96, 88.2, 48, or 44.1kHz sampling rates, 24-, 20-, and 16-bit wordlengths, selectable dither and noise shaping, AES/EBU and S/PDIF digital outputs, word clock sync input and output, separate analog and digital output controls, 60dB of gain and +/- 15dB of output gain, a selectable mic/line switch, 48V phantom power, a 75Hz low cut filter, phase reverse, 12 segment LED, and a 20dB pad. With its impressive features, it lets you work in the digital world while retaining the indispensable warmth of analog.
  11. lazyshark

    lazyshark Guest

    I meant two extra mic inputs. The Audio Buddy doesn't have S/PDIF, I know. I thought I explained it. Microphones -> Audio Buddy -> which gives me line level out -> line into an A/D converter which has S/PDIF out (Audigy 2 soundcard on my other computer) -> into my Mbox 2. Does that make sense? Or am I missing something? So 69 bucks adds two microphone inputs to my Mbox 2. Let me know if anything is unclear, or if I've misunderstood something.

    My Mbox/ProTools setup is fine, I'd just like to have two extra mic inputs for recording drums. Two for RecorderMan OH thingy pointed a little at the toms, and close mic on snare and kick. And if I've understood things correctly, I can achieve this with the Audio Buddy. I know it's not the most conveniant way or the best way. The DBX unit looks great, but I'm a college student, which means I'm broke pretty much all the time. I just want to record songs with my band. So until I can afford the really good stuff, I'll make use of what I have and try to get it to sound as good as possible. :)
  12. Reggie

    Reggie Well-Known Member

    Dec 20, 2004
    That just might work. The thing I'm not sure of is if the Audigy can route its line input directly through to its digital output, without having to first record the signal and then play it out the digital out. Prolly works, but I've never tried.
    I do have a somewhat similarly convoluted setup going right now. My old monitors used to have two sets of inputs, so I had my RME Multiface and my Audigy outputs all hooked directly to the monitors. My latest monitors (BM6A) only have one XLR input, so now in order to route all the Windows sounds and stuff to the monitors, I route a cable from the Audigy digital out into the Multiface SPDIF input, and route that via the TotalMix software mixer to the analog outputs that connect to the monitors. Crazy, huh?
  13. lazyshark

    lazyshark Guest

    All is good as long as it works right? :wink:

    Yeah, if the Audigy can route the signal directly is the only thing I'm not sure of yet. I guess you should be able to monitor your line-in signal. It's probably only a software issue in any case. And I'm not quite sure how I configure the A/D converter to 24-bit/48kHz to match my Pro Tools sessions. I'm not sure how that even works, because I can record S/PDIF in an 24-bit/48kHz session in Pro Tools, when the signal coming from the S/PDIF is only 16-bit/44.1kHz. Which means Pro Tools converts right?
  14. Reggie

    Reggie Well-Known Member

    Dec 20, 2004
    I believe my Audigy defaults to 48k on the digital output so maybe you'll be OK. I think you'll have to have some kind of recording software program open to activate monitoring through the digital out, but again I don't know. I don't recall the Audigy having its own routing software other than a levels mixer. And I really don't know how much hell you would go through with latency and all. Try it and see is the best advice I can give you.

    Not necessarily. It probably means your recording will sound off-speed when you play it back since you configured ProTūlz to handle 48k files, but you have fed it audio digitized at a rate of 44.1 .
  15. Kev

    Kev Well-Known Member

    Nov 13, 2001
    so you are prepared to use the Audigy 2 soundcard as the primary Audio Clock source to drive the PT mixer.

    Then you are going to use the EL-cheapo Mic-pre and convert the analog line out from a sensible connector to a stupid 3.5mm stereo crappo and enter an electrically NOISY environment of the computer and then use the EL-crappo A/D converter of the Audigy.

    With unstable clock you now have two channels of digital audio ... and it's inherent latency.

    This SPDF will then drive the M-Box 2 and give PT it's audio clock source to which the M-box will try to add the two Analog Inputs ... These Mic-pres will be fantastic quality compared to the other two BUT will now have a shifting clock to deal with.


    if it all works
    you may get 4 channels of record in one pass.

    Oh yes
    Explained it fine
    Nothing is unclear

    It's still not what I would call an upgrade.
    2 to 4 may seem good but the step backwards in quality is just not worth it. Save a little money and get a real Mic-pre with the SPDF facility
    a real Mic-pre and a stand-alone SPDF unit.
    If you get a quality Mic-pre now ... you will still be using it long after the M-Box has been thrown in the bin.
    The same goes for quality Microphones

    You have plenty of fine people here to help
    so I'll get out of the way now.

    it's all good
  16. Reggie

    Reggie Well-Known Member

    Dec 20, 2004
    Aw man, you ruined all the fun. I was just about to break out the duct-tape, ball-point pens, and the Swiss Army knife. :D
    Yeah, this setup would certainly be ghetto as heck if it works, but I was just thinking as far ahead as getting it to work.

    If homeboy has any money at all, he would probably be better served by getting a 6 or 8-input mixer, and feeding the stereo sum into his MBox. No shame in that.
  17. Kev

    Kev Well-Known Member

    Nov 13, 2001

    yep, a borrowed mixer for the times when more in one pass is needed.
    edit is not so good but
    we lived with sound on sound not so long ago

    what am I doing !!
    I'm not here
    run away run away
  18. lazyshark

    lazyshark Guest

    Hey, I'm broke, and I happen to watch MacGyver alot.

    Well actually speed/pitch is correct.

    And that would be worth it for now. It's not like, if this all works, I'm not gonna get somethnig better later. I still have to save up to get something better. Or is getting great gear better than getting experience just recording something, even though quality isn't top notch or even close?

    It's all good. I appreciate your replies and your input.

    With the 600 i spent on my Mbox (here in Norway), and another 500 (which comes to 750 for me) for the dbx, I might as well sell my Mbox and get a 002 rack or ProjectMix I/O, or something different entierly. Guess I'll just overdub kick and snare for now, and leave the quality of that up to my drummer. :wink:
  19. Kev

    Kev Well-Known Member

    Nov 13, 2001
    we like RDA (Richard Dean Anderson)
    and his fantastic abilities with paper clips and string

    then keep working on it

    correct !!
    and this is why , when we give advice here about interfaces choices
    WE stress, just how important it is to know the number of simultaneous record inputs required.

    An M-box and a Neumann and an ISA430 is perfect for a soloist that predominantly overdubs
    ... has a good budget
    The Project or 002 or even better 001 with ADA8000 on XP is best for Band with Drum Kit
    ... on a tight budget

Share This Page