DI or preamp: What's the difference?

Discussion in 'Acoustic Heaven' started by Charlie Bernstein, Nov 1, 2019.

  1. Charlie Bernstein

    Charlie Bernstein Poster Extraordinaire

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    I've read explanations but still don't get it. Can someone explain in plain, non-electrical-engineer English?

    Thanks!
     
  2. 24 track

    24 track Doctor of Teleocity

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    A preamp adds an amplified gain stage to your signal
    A di is a device to give you line level that a mixer can register Usually using a transformer ( for a passive circuit or non powered)
    or a line matched circuit for an active DI ( powered)
    A Di will also give a separate output to go to your regular guitar amp as well as a pad of some kind to increase or diminish your signal if it is too strong

    is this too technical?
     
  3. Dacious

    Dacious Poster Extraordinaire

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    The DI matches impedance of a high impedance source to a low impedance desk input.

    There's DIs, and DIs. Usually people are referring to battery or phantom-powered units.

    If you plug an electric or a acoustic with a piezo straight into a mixing desk or recording console can find a big loss of signal and attendant treble, middle bass characteristics - crap sound, basically. Turning the controls up just adds noise.

    The DI usually has a jack input with XLR and often if powered an opamp buffer which will kick the signal up through a long cable and avoid losses. It gives the sound mixier something to work with. The result is both quieter and better sound quality without pushing the gain into clip. Nice clean sound.
     
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  4. Charlie Bernstein

    Charlie Bernstein Poster Extraordinaire

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    Both descriptions make sense. Now I get it. Thanks!
     
  5. Thin white duke

    Thin white duke Tele-Afflicted

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    I use both, problem solved. :lol::lol::lol:
    If you need to play into P.A. i suggest you to use both, in my case i find a lot of benefit with an amp. sim. because of the eq., feature that a d.i. doesn't have.
     
    Last edited: Nov 2, 2019
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  6. AndyPanda

    AndyPanda Tele-Meister

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    To muddy the waters .... you can buy a preamp with a DI built in and you can buy a DI with a preamp built in.

    A straight DI can be passive (a transformer - no battery or active electronics) just to convert your 1/4" high impedance guitar signal to XLR, balanced, Low impedance signal suitable for a long cable run to the mixer. Or a DI can be active and instead of a transformer it uses electronics to buffer and convert the signal to low impedance, balanced output.

    A SansAmp pedal is a DI that has a preamp built in that emulates the sound of a amplifier and speaker - when you are in bypass mode (no amp emulation) it still works as a DI. I've had good luck using a Behringer knock off of a Sansamp pedal as a preamp to drive a tube poweramp - the DI output doesn't even need to be used at all, but it's there if you need it.

    The purpose of a DI is to convert hi impedance, unbalanced signal to low impedance, balanced signal.
    The purpose of a preamp is to add gain - for example to drive a power amp.
     
    Last edited: Nov 2, 2019
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  7. Freeman Keller

    Freeman Keller Tele-Afflicted

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    That has always been my interpretation. Piezo pickups are typically are very high output impedance, on the order of 1 Megohm. If it is connected to an amplifier designed for a coil type pickup with 5 to 15 Kohms of impedance the amplitude of the signal will be reduced. The DI or the on board preamp can match those differences.
     
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  8. Dukex

    Dukex Tele-Holic

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    The DI (Direct Injection) box primary function is to take the unbalanced, high-impedance signal from electric guitar pickups and transform it to a balanced, low-impedance (mic level) signal of a mic preamp.
     
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  9. Axegrinder77

    Axegrinder77 Tele-Meister

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    I have both my acoustics equipped with kk western mini (passive) pickups. I purchased the kk pure preamp (the small one). It helped a bit, but I find the tone still not optimal going into the board.

    Should I add a DI? This would convert it to xlr, right? Would there be a benefit?

    Thanks!
     
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  10. Sev112

    Sev112 TDPRI Member

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    Hugely too technical, but not as technical as the ones that followed

    What is “line level” ? And presumably it is higher than instrument level, it involves some form of amplification? So how is it different to a pre amp?
     
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  11. 24 track

    24 track Doctor of Teleocity

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    this may get a little more technical

    A mic-level or microphone-level signal describes the voltage generated by a microphone when it picks up sound, typically just a few thousandths of a volt. This voltage varies in response to changes in sound level and distance. Of the four main types of audio signals, mic level is the weakest and requires a pre-amplifier to bring it up to line level.

    A line-level signal is approximately one volt, or about 1,000 times as strong as a mic-level signal, so the two do not ordinarily use the same input. This signal travels from your pre-amp to the amplifier that powers your speakers.

    A mic-level input is typically a female XLR connector. A line-level input is typically an RCA jack, 1/4" phone jack, or 3.5 mm phone jack

    there are numbers associated with some of these statements but for your purposes they would be "overtech" for your question

    so to recap Mic level would require a preamp stage ,


    I took this from an on line site as the definitions were more consise than I could put into words

    https://www.shure.com/en-US/perform...ts-the-difference-between-line-and-mic-levels

    • If there is only a mic input on a device (for example, a digital recorder or a computer) and you need to connect a line level device to it, you can reduce the voltage by using an attenuator or a DI (Direct Injection) box, available at most music stores. There are even cable versions with built-in resistors that accomplish the same task.


     
  12. Dukex

    Dukex Tele-Holic

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    Mic level is generated by a mic and is the lowest/weakest. It requires a mic preamplifier to bring it up to line level.

    Instrument level signals fall between mic level (lower) and line level (higher) signals. Many mic preamps have a 1/4" unbalanced DI input (which bypasses the mic input) for Instrument level devices (guitars). By using a DI box you can plug into the balanced mic input and take advantage of any transformers or tubes in the mic gain stage.

    Line level signals are the highest level signals. This is the standard signal used by most recording equipment.

    Both Instrument and Mic levels are converted to Line level by a microphone preamp.
     
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  13. Charlie Bernstein

    Charlie Bernstein Poster Extraordinaire

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    Yeah, I use a Sansamp Blonde, a passive Radius JDI, and a Red-Eye acoustic preamp, among other things. And I've had a few other preamps.

    I know how to use them and the difference between a passive and active DI. I just could never figure out what makes one thig a preamp and another a DI.

    Your comment about how some units are combinations of the two is probably part of my confusion. Glad you pointed that out. Thanks!
     
  14. Charlie Bernstein

    Charlie Bernstein Poster Extraordinaire

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    Yeah, my dread has a K&K mini, my resos have K&K Reso SBs, and my mando has a K&K Mando Twin Internal.

    You're right, K&K tones don't particularly match the PA's electronics. So I have four EQ pedals on my board, one in front of each instrument. That way I can get them all set right (in theory) before a gig starts and switch instruments at will.
     
  15. Vizcaster

    Vizcaster Poster Extraordinaire

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    It depends on how you are going "into the board." Some mixers have high-Z inputs meant to plug an acoustic guitar in directly. However most of the time if you see what looks for all the world like a 1/4" phone jack it probably is not expecting you to plug in a guitar cord. Instead it's probably a TRS expecting you to plug in a balanced cable for things like keyboards (hint - if the jacks are in pairs for stereo on the same column of the mixer, they're probably for TRS balanced signals at line level). Generally the gain knob or pad switch will adjust for the specific impedance of the source, but you need to be in the ballpark of what that input was meant for.
     
  16. Charlie Bernstein

    Charlie Bernstein Poster Extraordinaire

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    I've always wondered that, too. What line?

    Lately I've been thinking that maybe it just means the amount of signal that comes from a passive (no battery) guitar pickup - which I guess might be different that the signal from a microphone.

    One is low impedence and one is high. They say. I don't know which is which or what impedence is. Is it anything like impudence? Maybe mikes are more impudent than pickups. Like my old buddy Mike Schwartz, for instance.

    And then, where does phantom power come in? When do you use it? What's so phantom about it? I always think of that jungle guy with the purple tights and forty-fives and a ring that leaves skull marks on bad guys' jaws.

    All the electronics books I've opened are written for people who already know something. I've wished for years someone around here offered an entry-level (not line-level) electronics course. No such luck, Chuck!

    phantom2.jpeg
     
    Last edited: Nov 8, 2019 at 12:30 PM
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