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AD/DA converters?

Discussion in 'Converters / Interfaces' started by tempest1226, Aug 19, 2009.

  1. tempest1226

    tempest1226 Guest

    Very newb question here, but its driving me nuts. haha. What exactly are the rack mount converters such as the apogee 800 used for. I know it says it's to convert your analog audio to digital but what does that mean really. For example if I am using a Digi002 with protools 8 into a Apple mac, is this something that can make my sound less artificial/digital if I'm using stuff like the line 6 pod or what. lol. Sorry for the stupid question but I was hoping to learn what this can do for a studio in detail and I have done research and reading the specs and what they do on the retail sites isn't clicking with me. haha. take care friends!!!!
     
  2. TheJackAttack

    TheJackAttack Distinguished Member

    Your Digi 002 also has analog to digital converters. Every computer interface has AD converters of some sort, and many also do the reverse-DA-for monitoring or other output. The Apogee converters are just a different flavor of AD conversion. Are they better than the 002? Do you like Coke or Pepsi. It's about the same decision.

    Now, there are low end units where there is a definite difference between the AD conversion chips and circuits when compared to middle or high end products.

    There is much less difference between the middle grade conversion circuits and the high end converters. Negligible in fact for the average Joe even if he isn't a plumber.

    Better to worry about learning gain staging and microphone placement than about the quality of AD conversion on a Digi 002. Those are things that will take you lots further in the subject of audio engineering.
     
  3. fourone3

    fourone3 Active Member

    If you wanted different converters, use the ADAT in on the 002.
     
  4. BobRogers

    BobRogers Well-Known Member

    As John said, the 002 has AD converters on each of the 8 analog input channels. The 002 also has 8 channels of ADAT input. You could, for instance, use an Apogee Rosetta 800 and 8 channels of outboard preamps to give yourself 16 channels. (This is a bit of overkill since the 002 limits the sample rate if you use all 8 channels.)

    I'm also with John that you should not obsess about converters -especially if you are starting out. (Sure, learning about them is fine.) Yes, there are differences - as there are in every piece of equipment. But those differences are small, and in many cases I'm not convinced they are even audible. (It is hard to isolate the converters in an integrated interface, so it's hard to directly compare the converters in, say, an 002 and a Fireface. When people make big claims about things that are hard to test, hold on to your wallet.) If you are just starting out, you will learn several dozen things in the next year that will make more difference to the sound of your recordings than the difference between the converters in the 002 and the best that are currently available.

    Another reason not to get hung up is the investment problem. Suppose that in 1989 (or even 1999) you had invested $5,000 each in microphones, preamps, and converters. Today, the mics and preamps would be worth more than you had paid for them. If you chose wisely, a lot more. The converters would be worthless. As they say in the ads, " Past performance is no guarantee..." but I know where my money is going.
     
  5. sshack

    sshack Active Member

    Very well said Bob.
     
  6. Cucco

    Cucco Distinguished Member

    I agree with Bob and John. Though the topic here isn't necessarily about the differences in quality of AD/DA converters, it's certainly an ancillary topic of note.

    Ironically, the ability to test the differences between AD and DA converters isn't that difficult; however, very little people actually do test them. The tests could range from very simple and subjective to moderate and containing some objectivity to down right scientific. It's easy to send the exact same signal to 2 different (or more) AD converters and compare their signals to the original. Sadly, this does involve a few other variables such as the source itself, the cables and means of performing the split. However, these can either be minimized or even accepted given a broad enough sample (perform the test a few times and determine if the results are consistent each time).

    I've had the pleasure of working through Prism ADA Dreams, DCS and a couple other "high end" ADs as well as AD from RME, Lynx even down to ART!

    I'd be very weary of anyone who would indicate that the A/D conversion is one of the more critical components of sound.

    I'd also be cautious to suggest that the AD in the 002 is the cause for making things sound artificial or digital. While, in general, I don't care for much of the 002 (including its conversion), in the grand scheme of things, it's not a *bad* box, it's just not up to par on for the price it commands.

    The short answer to your original question -
    An AD's function is to translate voltage (analog audio) into binary (digital signal) representations of that voltage. The DA performs the exact opposite function. Many of the converters on the market use the exact same chips for this function. The most common are TI, Burr Brown, and AKM. The biggest difference in virtually any converter lies in its analog stages (the quality of the components and the circuit topology) and its power supply.

    This being said - a general (but not golden) rule is - the heavier the AD/DA, the better the sound. It's a loose correlation, but generally, heavier devices include more robust power supplies and more solid analog components (maybe even a transformer or two if that's your bag.)

    Cheers-
    J.

    PS -
    Welcome to RO!
     
  7. MadMax

    MadMax Well-Known Member

    John and Bob very well described the situation with the converters. So there's no sense getting into that...

    But your statement of; "make my sound less artificial/digital" is one which, I hate to say it, is more of a philosophical one by its sheer existence...

    Artificial and digital have become errantly associated.

    Though, one would think that it would be obvious that to get less of an artificial sound, e.g. more natural sound, one would simply choose to use a natural instrument.

    There in lies the rub.

    An acoustic guitar is a natural instrument... except Ovations.... but what about a stack of triple rec's with 8 double stacks of 4x12 Marshall cabs?

    Is that anything near as natural as a Martin D-35?

    You can argue the point ad nauseum, but you get to the fact that at some point, anything that is actually used to create a cultural performance is indeed and instrument.

    I'm guessing you're actually hinting at the fact that a pod sounds like digital ass compared to a true class A tube amp glowing cherry red from cookin' out some nice gritty, screamin' blues slide.

    Guess what?

    You want analog?... the easiest thing to do is just plain use analog.

    You want digital?? the easiest thing to do is just use digital.

    Don't expect analog to sound like digital and don't expect digital to sound like analog.

    The two are not the same thing, nor can they ever be.

    Period.

    End of discussion.

    If you wanna talk about DSP modeling... meh... jebus... that's a can of worms. It's close, and maybe it's close enough if you actually take a professional attitude and actually learn the technique and thereby set yourself with that skillset... or you're somehow happy with the sound.

    But all too often, the reality is that analog amps simply smoke cheap digital emulators. Hell, gimme a PigNose and two SM57's and I can make you sound like you're plugged into the Niagra Station of Con Edison compared to most of the other pro-sumer type digital whizbang pedals.

    Then too, a few too many plank spankers are all about "their" sound, instead of being versatile enough to play any style of music that can bring potential income in....

    Ooops........


    Oh jeeze.... did I just drop some napalm on the floor?


    ( "We have a clean up on aisle 5, please." )


    Look, if you don't like the digital artifacts that exist in your modeling... guess what again??? It ain't going away...

    The only way to get rid if digital artifacts is to just simply not capture the artifacts in the first place.

    If you can't avoid the artifacts.... tough... you got em' and spending more and more money trying to correct something that can't be fixed is silly.

    Bottom line... You want an analog signal? You gotta start with an analog signal.

    The point then becomes the pretty well established reality of converting that signal to a digital storage medium.

    The goal of your A/D process is to convert the widest dynamic range within the converter's input ability, without approaching the last non linear portions of a converter's curve... which are the two extreme ends of the volume spectrum.

    You convert as accurately as you can, and then you have control over the rest of the processes, sans artifacts, clipping and distortion.


















    (Now where the hell did I put my asbestos underwear????)
     
  8. tempest1226

    tempest1226 Guest

    wow, thank everyone. I def learned a lot. I guess originally I had been curious in understanding more about ad/da upgrade because I recently discovered the magic of reamping and have heard (but who knows), that converters could make or break the quality of playback through the amp as well as the dry signal recorded through the input. How much of a difference, i'm not sure. Is this something that holds any truth?
     
  9. TheJackAttack

    TheJackAttack Distinguished Member

    I think at the level of gear equal to or in the same range as a Digi 002 it won't be about converters. It will be whether or not you like the aural signature of the analog circuitry before the AD and after the DA.

    The converters themselves will have a negligible affect with that minimum standard of gear.
     

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