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Amp, PreAmp, DI?

Discussion in 'Amps and Cabs [BG]' started by Jacer, Dec 26, 2019.

  1. Jacer


    Dec 26, 2019
    So I’ve been playing bass since 4 years ago and until today I’d not been interested in these topics. But now I want to buy something that make my sound tastier.

    But in my way to get some information about this topic I found a lot of options and some terms I’m not familiar with.

    So, making it simple, I want to know what does an amp, pre amp and DI are? What do they do to your sound? And in wich cases you will need them?

    ¡Thanks a lot for your help!.
  2. An amp is anything that makes the signal bigger.

    In terms of bass amps there is the preamp and the power amp in one box. It may have a DI as well.

    The preamp takes your instrument signal and makes it bigger.
    Power amp takes the signal from the preamp and turns it into speaker level signal.

    A DI sends a signal for front of house mixer or recording. It can do that without picking up interference for 100m. These days a lot of amps have a good one built in.
    dbbltime likes this.
  3. Yummy Notes

    Yummy Notes

    Dec 20, 2019
    Sound Tasty?...this feels like a nice thread for a first attempt from me.

    I have been lurking on TB for a while, just learning new things.

    A preamp raises the bass signal to line, and the amplifier then amplifies the signal for dispersion via the speakers.

    I believe the DI only converts the unbalanced signal from the bass to a balanced signal, so it may be plugged into a mixer board or other device at mic level. (The mixer would then raise the signal from mic to line and send to PA system).

    The bass head, which includes the preamp and amplifier, is the portion that would impart the character, i.e., your sound.

    Warning: the rabbit hole can get deep... type of preamp, type of amplifier, cabinets, etc.

    I'm certain the other TB members will add much more informative posts soon.
  4. Samatza


    Apr 15, 2019
    So to make it clear what have you been playing through for four years?
  5. pravus


    Feb 5, 2013
    Denver, CO
    The term "amp" or "amplifier" is used pretty loosely in the audio world but in general will refer to a piece of equipment that will both shape the tone of your instrument as well as electrically magnify the signal coming from the instrument to a speaker system. When used alone it typically refers to just the "head" unit. If you have a "combo" amp that means that you are getting a head built into a speaker cabinet as an all-in-one unit.

    Now, that being said, each amp is usually divided into two major stages: the pre-amplification stage and the power amplification stage. The power stage is the easiest to understand because it just takes an input voltage and multiplies it electrically to an output. There's no tone shaping and you have a single "master" or "volume" knob to control the amount of amplification. The output of the power stage is measured in watts and this value can roughly be used to gauge the loudness of amp.

    The tone-shaping stage is known as the pre-amp. This is where all of the bass, mid, treble, bright/dark, gain, etc. controls are found. This stage is a low-voltage amplification circuit that only exists to modify the various audio frequencies produced by the instrument. It is fed into the power amplification stage.

    So that covers your typical "amp" but there are also specialized devices that may only serve one of the stated purposes above. For example, it is possible to buy just a power amplifier that has no tone shaping and is only used to drive a speaker cabinet. Conversely, a "pre-amp" will normally only be the tone shaping circuitry and won't include any sort of power amplification at all. This allows you to mix and match tone and power variations for all sorts of audio applications.

    So you might ask what happens to a signal if you have no power amplification to drive a speaker cabinet. That's where DIs come in. A DI is just an output that allows you to plug directly into another piece of equipment for signal processing. The easiest example is simply coming out of a pre-amp into a mixing board for recording or going to a house PA. This is also how you connect things together when using a separate power amp since the input to the power stage will usually just be a DI from another amp, dedicated pre-amp, or even just a pedal-chain.

    I hope that helps a bit and welcome to the wonderful world of amplification :)

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