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What's a pre amp all about?

I like starting topics to help the new recording enthusist better understand things each step of the way. Let's ask Sebatron some really basic questions about pre amps.


  • what is a pre-amp all about?
  • There seems to be more and more pre-amps hitting the market, what is all the hype about?
  • I thought pre-amps were in the mixer, why do we see them sold as a single unit too?
  • what makes a good pre-amp more desirable than another?
  • are quality pre-amp's more important for digital recording?class="xf-ul">
  • Comments

    scottmcclure777 Wed, 01/14/2004 - 23:26

    I am not an expert on this but I will tell you what I know. A pre amp is useful for warming up vocals or instruments like a guitar or bass, it can also give you lots of room for volume. There are 2 types of pre is tube and the other is solid state, the tube pre amp gives you more of an analog warm sound where as the solid state has more of a digital sound to it. As with anything let your ears be the judge of which one you like...I personally like tube for it's warm sound..although they can get noisey. I think that a pre amp is very necessary for mic if you are going to record vocals use a tube pre amp with some compression. :D

    Sebatron Thu, 01/15/2004 - 17:22

    what is a pre-amp all about?

    At its simplest , the pre-amps function is to act as an interface between the microphone ( or a direct instrument input ) and the DAW/Reel to reel etc
    .The pre-amps function extends out to supplying Gain ( voltage magnification ) and also preferably a low output impedance ( current magnification ) .

    In one aspect it must do this in a transparent or ‘colourless’ way , so that we may get closer to the natural or real sounds that are picked up by the microphones etc…
    In an extreme case ,, a ribbon mic hooked up to a pre-amp would need a significant amount of gain before it can drive a soundcard properly….it would obviously not be able to do this without the pre-amp.
    On the other hand ,, some mics put out a massive signal ( condenser mics for example ) and the relative amount of gain needed is substantially less.

    There seems to be more and more pre-amps hitting the market, what is all the hype about?

    There are so many ways a pre-amp can be designed and built …
    Each manufacturer will obviously promote their particular methods as being the best or most suitable for your requirement. Each method will yield different sonic results ….
    Sometimes only a very small difference.
    This difference becomes apparent as tracking or multi-tracking takes place.
    Other differences may be realised when mixing takes place …. i.e how easy is it to mix….

    Sometimes this hype can be misleading , or just plain Bullshit …. As is the case with S.M.D circuitry.
    S.M.D circuitry is cheap and easy to assemble ( sometimes by Robots ).
    It is the kind of shit we see in mobile phones…..and domestic T.V sets etc.
    S.M.D is the next generation of intergrated circuitry …. been out for quite a while now.
    Some manufacturers love S.M.D because their so cheap and easy to assemble ,, that’s why they use them…..and they’ll try and push this as a positive aspect.
    I’ll tell you now …..S.M.D has no soul. :( :td:

    …. The Topology.…..Tube ,FET or Transistor? ….. Class A or B ?
    It can be subjective…. Sometimes it isn’t even relevant.
    However, valves are desirable because they complement the linear behaviour of current Digital systems so well.
    Out of all the possible circuit types , the valve operates closest to the human ear ….and consequently sounds ‘natural’ when pushed. That’s why we use ‘em.
    Transistors are desirable because of their transparency when operating in their comfortable zone.
    However , they do not gracefully ring like valves do when they are pushed to their limit.

    I thought pre-amps were in the mixer, why do we see them sold as a single unit too?

    In a typical mixer the pre-amps are usually of inferior quality when compared to dedicated units.
    Usually this is because of excessive circuitry in the signal chain like buffers that are needed to keep boosting the internal operating signals.
    Power supplies may also be inadequate resulting in restricted headroom and consequently distortion.
    The addition of a parametric E.Q that can’t be switched out almost renders some mixer pre-amps useless when compared to accurate dedicated units.

    what makes a good pre-amp more desirable than another?

    For starters , a good mic pre-amp should supply you with a decent amount of clean gain… transparent gain.
    It should also have the basic features that will allow you to operate your microphones with many different sound sources….. loud and soft ,, without freaking out.
    It should be able to operate throughout its range without noticeably changing colour or character.
    Noisefloor is another important issue as is transient response.
    A desirable pre-amp is quiet and quick….

    are quality pre-amp's more important for digital recording?

    Quality pre-amps are always important if you want to achieve a detailed and full-bodied sound.
    The advent of digital recording has only highlighted the need for accurate pre-amplification because of the linear Digital accuracy.
    Some pre-amps will stand out from the rest.
    Pre-amps that have a dynamic soak usually are the desirable ones for most applications.This is because they are musical in nature and will speed up your recording process by ever so mildly compressing each signal so that minimal compression is needed when mixing or mastering.
    Audio Transformers and Valves are one way for this to happen in circuitry. :tu: