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What does DI mean?

Discussion in 'Recording' started by Guitarfreak, Feb 27, 2009.

  1. Guitarfreak

    Guitarfreak Well-Known Member

    Forgive the nooby question. I thought it was one thing, then after hearing it discussed I am now thinking it is something else. Can someone clarify?
     
  2. jordy

    jordy Active Member

    it stands for just DO IT!!!!

    no...DI stands for Direct Input. ya know like going directly into a board or interface rather than micing up the guitar cab.
    they make DI boxes for doing just that.
     
  3. Guitarfreak

    Guitarfreak Well-Known Member

    Awesome thanks! Does the phrase only apply to electric instruments? i.e. can a vocal track be considered DI?
     
  4. jordy

    jordy Active Member

    vox usually are DI...so i think mainly people refer going "DI" with guitar, bass and keyboard etc...- usually stuff that you can use an amp for, but opt. not to
     
  5. StephenMC

    StephenMC Member

    A DI box for vocals makes no sense.

    What a DI box does is this: it takes an unbalanced signal, like one from a guitar or keyboard, and balances it (it doubles the signal and reverses the polarity of one). As the signal travels down the DIed cable out of phase, any noise and interference picked up will enter the signal in phase. At the end, the signal goes into a differential amplifier and inverts the phase of one of the signals. That way, the noise is knocked out of phase and canceled completely and the signal is doubled.

    Vocals are already going through this as you ought to be using an XLR cable and if you're not shame on you. An XLR carries a balanced signal and doesn't need a DI box to balance it.

    There are also impedance reasons to. A guitar carries a high impedance signal and a mic carries a low impedance signal. And sometimes you'll carry a line-level signal and you'll be bringing it into a mic level input which is silly, so some DI boxes may be able to level match.

    It mostly has to do with noise, though.
     
  6. jordy

    jordy Active Member

    stephen, i think we may have a miss communication here. when i said vocals are DI already, i in NO means ment to have one think i ment to go through a DI box.- that's a pointless add to the signal chain. by saying vocals are already direct, i simply meant that they go directly into the preamp/interface/mixer....sowwy for the mix up
     
  7. BobRogers

    BobRogers Well-Known Member

    A mixing board works with (1) low impedance (2) balanced (3) line level signals. Electric guitars produce high impedance, unbalanced, instrument (low) level signals. Mics produce low impedance, balanced, mic (lower) level signals.

    Basically a DI (e.g. this) changes high impedance to low and unbalanced to balanced; a preamp changes low impedance, balanced, microphone or instrument level signals to line level. The confusing part is that a lot of preamps (most?) have a DI as part of the package and some DIs (e.g. Line 6 PODs) have a preamp as part of the package. There are no real rules as to what to call such things so the decision is in the hands of the marketing department.
     
  8. Guitarfreak

    Guitarfreak Well-Known Member

    Thanks for all the good info. If I am understanding correctly, leaving out the combo packages...

    A DI is for 1/4 inch inputs and a Preamp is for XLR inputs? Not strictly I know but at least it sounds like they work best that way right?

    Forgive me if I am totally wrong. Gear is not my forte. :D
     
  9. StephenMC

    StephenMC Member

    Oh, no, I understood that. I was replying directly to him, hah. You did good, Jordy.
     
  10. Davedog

    Davedog Distinguished Member

    The people who invented this little process, ie: The engineering department at Abbey Road always referred to it as Direct Injection. They called the device a DIT, or Direct Injection Transformer. It was used to convert a high impedance signal to a balanced low-impedance signal in order to make long runs of cable back to the control room. It was used, at first, primarily for the bass signal from Pauls bass because they werent getting as good a sound in the control room monitors as they were getting at the amp in the studio. This wasnt used as much as one might think at the time. It was developed by Beatle engineer Ken Townsend.
     
  11. Guitarfreak

    Guitarfreak Well-Known Member

    cool background info. So was this little box used BEFORE the long run of cable (Bass side)? because that would make sense to me. If used at the END of a long run of cable (Studio side), it would seem to me to do a similar job as a preamp or basic signal booster. I know that you said it changes impedance from high to low, but I'm just clarifying how one would use such a device.
     
  12. Codemonkey

    Codemonkey Well-Known Member

    Use of a DI, explained by 5 minutes in MS Paint.
    With added bonus extra.

    guitar-recording.gif

    Edit: whoops.
     
  13. moonbaby

    moonbaby Mmmmmm Well-Known Member

    No. You place the DI close to the instrument so that THAT cable (between the instrument and the amp and/or DI is short. The DI can shove the signal down a l-o-n-g cable (like a PA snake) up to +500 feet if necessary.
    In fact, that is how many DI's are used these days, to run an instrument's signal out to the FOH mixing board. The ground isolation and low impedance of the DI make this possible...
     
  14. pr0gr4m

    pr0gr4m Well-Known Member

    Yes...Direct Injection is what I was taught.

    LOL...I absolutely LOVE MSPaint explanations. Do 'em myself from time to time. Photoshop, Schmotoshop!!!

    Next time throw in a bit of color.
     
  15. Codemonkey

    Codemonkey Well-Known Member

    Roger that.

    Should I paint the amp orange, the guitar red, and the DI blue, since orange amps are awesome (from a looks POV), red is also awesome (and makes your cars/plectrums faster) and I have a blue DI made by Samson.
     
  16. RemyRAD

    RemyRAD Well-Known Member

    It's also interesting to note, there are generally two types of DI boxes. Those that are passive & use a transformer. And those that are active, require a battery or phantom power and contain no transformer. Active DI boxes can only be used in one direction i.e. they are straight sexually speaking. Whereas transformer based DI boxes are bisexual & can be used in either direction. These types of transformer boxes can both increase level in one direction and decrease level in the other direction by virtue of the windings ratio of the transformer. These transformers are generally wound up with a ratio of 10: 1 or, when used in the other direction would be 1: 10 referred to as 10 to 1, or, 1 to 10. This is frequently the amount of gain or loss in DB levels. I like transformer D. I. boxes for this purpose as they can be actually passive amplifiers. And in a similar respect, a classic microphone preamp that utilizes a transformer input, provides extra gain so that the preamp doesn't have to work as hard. Conversely, when used with a electronic keyboard, those outputs are a type of line level signal. Line level signals are generally too high for most microphone preamp inputs and so the transformer D. I. box will take a high level signal & lower it so as not to overload the microphone preamp input. And in this process, it can actually take a balanced item to create an unbalanced item or vice versa.

    In certain circumstances however, transformers can "load down" certain items that don't respond well to being loaded down. Such as guitar pickups. This is where active DI boxes present a higher impedance loads to those items such as guitar pickups that can be adversely affected sonically by loading. Most transformers never have a higher impedance than 50,000 ohms. Whereas active DI boxes frequently have an impedance of 1,000,000 to 2,000,000 ohms, just as the tube inputs have on most guitar amplifiers. But again, those can only be used in a single direction.

    Good old TMI
    Ms. Remy Ann David
     
  17. TheJackAttack

    TheJackAttack Distinguished Member

    Most important-don't forget the knob that goes to 11....
     
  18. soapfloats

    soapfloats Well-Known Member

    Nice explanation Remy.
    Especially on the bisexual nature of passive DIs, and the advantages of an active DI in some situations.
    Today I finally had the opportunity to use the other sex of my passive DI box to reamp a guitar (DI) for a double track of a rhythm part.

    Now I will always DI guitars.
    "What? You have 4 vocalists? Sorry, I only have enough channels for two. We'll overdub those later."
     
  19. BDM

    BDM Active Member

    make the DI blonde, like the dead princess, whose hair grew for a year in the coffin...
     

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