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Switching Interfaces Midstream

Discussion in 'Converters / Interfaces' started by bradz, Jul 16, 2001.

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  1. bradz

    bradz Guest

    Hey Ya'll,
    Just wanted to say how much I appreciate this RO forum system. It's been SO helpfull to me as I build out my little Pro Tools room.

    Ok, here's the ??
    I'm going to start a record in another room tracking into PT. They have 888/24's, but I have 882/20's. After we cut basic's we're going back to my place for all the rest. Is it possible to start with thier 888/24 using a 24 bit session, then add new files from my 882's? If not, I'm going to have to cart my 882's in to cut basics.

    I've read that 20 bit words are really 24 bit words with the last four bits set to zero. Is this true??

    Thanks,
    Brad Zeffren
     
  2. Greg Malcangi

    Greg Malcangi Member

    Hi Brad,

    You won't have a problem. As far as recorded tracks or aux imputs are concerned the only relevant fact is the bit resolution of the session. Regardless of the interface resolution a 24bit SDII file will be created with the LSBs (Least Significant Bits) set to zero. This is true of 20, 16 and even 8bit files. However, if you are not recording tracks into the session but importing them then you will need to "Import and Convert" them. With my setup I use 888/24s for tracking/playback, etc., and a 1622 (20bit) interface for all my synth/sampler imputs. I've never had a problem.

    If you are looking for the maximum quality, make sure that you reference both the 888/24 and the 882/20 to a decent master clock.

    Greg
     
  3. bradz

    bradz Guest

    Good News! Thanks for the reply!
     
  4. bradz

    bradz Guest

    Hey Greg,
    I've been looking around today at Clock generator solutions, and I seem to be heading in the direction of the Lucid gear. Specifically, the Gen x6 word/superclock generator combined with an AD9624 converter. The two of them come in at around $1300, where the Apogee Rosetta is around $1050.
    What are your thoughts on these two brands?

    Can the Rosetta serve as the clock source? I wasn't able to tell from the lit. that I read.

    Also, is there an up or downside to using Superclock over standard Wordclock with the Digi gear? The Lucid generates both, but I'm not sure which one we should be using.

    Thanks,
    Brad
     
  5. Greg Malcangi

    Greg Malcangi Member

    Hi Brad,

    The Lucid gear that I've heard is quite reasonable. I haven't specifically heard the Lucid ADC/clock gen you mentioned so I can't give you any definate advice. On the face of it I would be more inclined towards the Lucid than the Rosetta. Having said this, I just want to check that you have already looked into how you are going to get the converted digital signal out of the Lucid and into PT.

    The only company I'm aware of that uses superclock is Digi. You must supply Digi hardware with superclock, they won't accept standard word clock. Anything else you've got that will accept a word clock input, DAT machine, outboard digital effects, etc., should be given it's own individual (standard) word clock feed. Don't daisy chain the clock signal!

    The Rosetta can act as clock source but I personally wouldn't want to, it's nowhere near as good as a proper master clock. Furthermore it's only got one word clock output so you would probably have to daisy chain the signal. Also, the Rosetta cannot be slaved to an external clock.

    You will find that a decent masterclock will greatly improve the sonic quality of an 888/24 or 888/20 and your mix in general.

    Greg
     
  6. bradz

    bradz Guest

    Ah ha,
    I see a fly in the ointment now. I need to send the 882's superclock sync, but the Lucid DAC wants Wordclock. Can't have 'em both coming off the same Gen x6 master.

    So then am I to assume that if I want to use another flavor of DAC, it either has to accept Superclock, or I cannot have a dedicated external masterclock in the system?
    The clock stability does play a major role in digital transfers as well as in the A to D conversion, correct? I would be coming spdif out of the Lucid DAC into the 882.

    How do all those folks that use gobs of Apogee channels in front of Pro Tools do it? Do I have to tradeoff stable clock for different DAC sounds, and hope the the increase in conversion quality will offset the errors introduced by an unstable clock?
    I guess I'm a tad confused...
     
  7. Greg Malcangi

    Greg Malcangi Member

    Hi Brad,

    << I need to send the 882's superclock sync, but the Lucid DAC wants Wordclock. Can't have 'em both coming off the same Gen x6 master. >>

    I've looked up the Gen x6 and I see your problem. It either allows you to output wordclock OR superclock, not both at the same time. I personally use a Nanosyncs master clock which also has six wordclock outputs but up to three of the six can be configured as superclock so I can have both wordclock and superclock referenced from the same master source. The Nanosyncs is distributed by HHB and I believe the cost in the US is about $1,000 - $1,100. It's made by Rosendahl in Germany but I don't know the web address off hand. The web site is worth visiting, read the online manual because it has a section dedicated to PT users.

    BTW, if you are going to get into this beware of jitter specs. Jitter specs only give you the jitter created internally by any specific bit of kit but can't give any idea of how much jitter is going to be added to your system by daisy chaining the clock in and out of the unit. Let me give you an example: Let's say you have an 882/20, with jitter specs of (for example) 30ps, a Lucid with jitter specs of (for example) 20ps and a DAT machine with specs of 25ps. Total system jitter of 75ps right? Wrong, a 2 meter cable run between each unit could easily double your system's jitter, let's say 150ps. With individual feeds from a masterclock like the Nanosyncs the only jitter you are going to get is the jitter from the Nanosyncs (about 10ps if I remember correctly) if the cable lengths are all the same this won't add any jitter to the system. Total system jitter of say 10ps as opposed to say 150ps, a serious difference, and the more bits of kit in your chain, the more noticeable are the benefits of a good masterclock.

    << The clock stability does play a major role in digital transfers as well as in the A to D conversion, correct? >>

    Correct. Depending on the quality of your monitoring environment you should notice improved stereo imaging and greater clarity and depth in your mix. In my chain I have; 2 x 888/24s, 1 x 1622, DAT machine. The improvement in my system was even noticeable by my office staff, who don't know the first thing about music or production. Everyone I've spoken to who has added a Nanosyncs to thier system would rather gnaw their own leg off than remove it again! BTW, Jules is around here somewhere, ask him what he thinks of the improvement in his system after he added a Nanosyncs.

    << How do all those folks that use gobs of Apogee channels in front of Pro Tools do it? >>

    One of two ways: Some use a masterclock and a clock distribution amp, others use the first AD8000 as a masterclock and a clock distribution amp to get it round to the other units. You can get away with this second option with the AD8000s because they have a pretty good internal clock. However a good dedicated masterclock will still improve the sonic quality even of an AD8000, although the improvement isn't as noticeable as with an 888/24 or 882/20.

    Hope this helps,

    Greg
     
  8. bradz

    bradz Guest

    Yeah,
    Now I get it!!
    So by adding a stable master clock, I can greatly improve the quality of my digi gear, and eliminate (at least in the short term world of tight budgetary constraints)the need for an added DAC in front. Would you suggest locking an outboard digital verb like the Lexicon MPX-1 to the master clock as well?
     
  9. Speaking of Nanosyncs, I have one in an unopened box--call me!
     
  10. Greg Malcangi

    Greg Malcangi Member

    Hi Brad,

    Yep, you got it! Having said this, there is of course still a great deal of quality you could add to your system by getting a 24bit ADC to replace your 20bit 882. But you should still notice an improvement in quality of your 882 and indeed of the 888 in the other room you were talking about. If sometime in the future you do get an new ADC make sure it can accept a word clock input. Invariably, however good it sounds, it will sound better with a really good clock reference.

    << Would you suggest locking an outboard digital verb like the Lexicon MPX-1 to the master clock as well? >>

    Absolutely. Everything you've got that has a word clock input or a video ref input should be connected to your masterclock. For example, if you get a Nanosyncs and have an MTP/AV then feed the MTP with video ref from the Nanosyncs. Same with a USD. The more bits of kit you can reference from the masterclock, the cleaner and better sounding your mix will be, even if it's analog outboard with only a video ref input.

    As an added bonus, if you ever have to work with video or film and therefore time-code, you will get a much quicker, more accurate and more stable time-code lock with a Nanosyncs.

    Although I can't vouch for him, if you can get a deal from Bert (Genius at Work), it's got to be worth considering.

    Greg
     
  11. I'm a Soundscape Digital dealer in Philladelphia PA (Soundscape used to distribute Nanosync in the US.) I got the box in on a special order, then the customer backed out--I'll sell it at a very good price! Call me Monday.
     
  12. SoFine

    SoFine Guest

    Greg,

    Could such a clock bring about considerable improvements using a Digi001. I plan to get a TC Electronic Gold Channel which is a stereo pre-amp / eq / fx etc. with 24 bit AD DA. This will replace me having to go through the not so great Digi0012 pre's and AD/DA. I also use a TC Electronic M-One - which I hook up by optical.

    So I will have 2 pieces of outboard:
    TC Gold Channel (my complete I/O solution - I never need to record more than 2 inputs at a time) - with digital optical IO
    TC M-One - great fx unit - with digital I/O

    Will a clock improve my situation - I would master it and slave the Tcs to it, wouldn't I?

    Thanks,

    Simon :)

    PS - I don't have any video sync needs PLUS I use a midisport USB 8x8 midi interface which may be relevant to my question.
     
  13. Greg Malcangi

    Greg Malcangi Member

    Hi Simon,

    I take it the optical out of the Gold Channel goes into the Rossetta. Here there is a slight fly in the ointment. I believe the Rossetta has word clock out but not word clock in, which means it can't be slaved to a master clock. You may still notice a slight improvement with a master clock if you slave your TCs and your mastering machine to it, but as you can't slave PT itself, much of the benefit of a good master clock will be lost.

    Greg
     
  14. SoFine

    SoFine Guest

    Hi Greg,

    Can you not slave PT over optical?

    Simon
     
  15. Greg Malcangi

    Greg Malcangi Member

    Hi Simon,

    << Can you not slave PT over optical? >>

    Yes, however there is a big "but". Whenever you connect two or more bits of equipment together digitally they automatically sync with each other. The first bit of kit in the chain (usually the ADC) uses it's internal clock to generate a word clock signal which is embedded in the digital audio stream. The next bit of kit uses this word clock signal as a reference, does it's processing and passes on the word clock signal to the next bit of kit and so on. This process is the same whether you are using SPDIF, AES/EBU or Optical. Although it works, timing delays are introduced as the word clock signal is daisy-chained into and out of each piece of kit, you are also at the mercy of the internal clock within the first pice of kit in the chain. These delays and clock inaccuracies are the cause of jitter. There is a way to bypass this situation with a master clock provided that the equipment in the digital chain has word clock inputs. A high quality clock reference is created by the master clock and fed individually to each piece of kit in the chain. Once your bit of digital gear realises that the clock signal is coming from an external source (the word clock input) it ceases referencing it's clock from the signal in the digital audio stream. You also eliminate the delays caused by daisy-chaining the signal and the delay introduced by each bit of kit. If you've got a piece of kit like the Rossetta in the chain that doesn't have a word clock input then it is forced to reference it's clock from the embedded signal in the digital audio stream from the previous bit of kit in the chain. To a certain degree, you are almost back to where you started before you went to the expense of buying a master clock. You may still notice an improvement but it's only a fraction of the improvement you should be getting. You are then forced to ask yourself if the slight improvement is worth the cost of the master clock and cabling.

    Greg
     
  16. SoFine

    SoFine Guest

    Greg,

    Thankyou my man. Nice answer. Clears it all up for me. I am not going to invest alot of squids in a clock when there will always be a weakest link (goodbye!) in the chain. I am however buying a TC Electronic Gold Channel soon, which has a very good pre-amps, ADDA and clock. I will only be driving PT from this clock so the chain will be short, at most I will add my M-One to this chain too occasionaly.

    Thankx again,

    Simon :)

    PS - Just bought Clavia Ddrums last weekend - W.O.W.
     
  17. Greg Malcangi

    Greg Malcangi Member

    Hi Simon,

    << Thankyou my man. >>

    You're welcome.

    << Just bought Clavia Ddrums last weekend - W.O.W. >>

    I haven't heard this bit of kit yet. Why do you rate it so highly?

    Greg
     
  18. bradz

    bradz Guest

    So here's a dilema,
    My Rig:
    PT mix+
    C24
    Langevin DVC
    2 RNC's
    Distressor
    Radius 20 Parametric
    With the cash I have, it's either some API Pre's to fill out my mic pre options (I need to be able to get good basic's here) or a Nanosync and maybe Lucid converter.

    Is it more effective to improve on the conversion of a lessor pre (C24), or introduce more jitter into a much nicer pre (API- I was looking at the 4 space single rack unit 3214m+ I think is the model #)
    using the digi as the clock master? decisions, decisions ....
     
  19. Ang1970

    Ang1970 Well-Known Member

    Have you heard what the DVC really sounds like? If you are only using the stock 888 converters and clock, you probably haven't. Beef up the clock first, and the converters, and maybe the DVC won't be headed for the tree belt so soon.

    Another thing to consider is the condition of your C24. Has it been cleaned and specc'd?
     
  20. bradz

    bradz Guest

     

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