advantages of a pre-amp?

Discussion in 'Amps and Cabs [BG]' started by dfreeman, Dec 11, 2002.

  1. I'm a little confused about pre-amps right now. I see outboard preamps like the aguilar DB 924, rackmounted ones, with and without effects, onboard ones, and ones built into an amp. The pre-amp built into my SWR just has a gain control and aural enhancer. I see these other ones that seem to have a million different things on them, and I don't know what the hell they do. I know basiclly what a preamp does, but I want to know what a seperate preamp can do for me. Is it just a matter of more tonal control, and maybe some effects? Can they really make a setup sound so much better? explain.
  2. Munjibunga

    Munjibunga Total Hyper-Elite Member Gold Supporting Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    As you recognize, pre-amps come in many forms, and are made for many applications. When you buy a full-power bass amplifier, it has a built-in pre-amp that typically includes an input amplifier (controlled by the "gain" knob), some form of EQ stage, usually either graphic (sliders), semi-parametric, or "shelving", and a power amp at the output stage.

    An alternative to a self-contained unit is to use a rack-mounted preamp, like an Eden Navigator, Kern 777, Demeter or any of a myriad of others. All of the EQ, compressor and signal-routing features (for effects, etc.) are included in this unit. The output from the preamp is sent to a separate power amp before going to the speakers. This setup is really keen for high-power applications, because you can run the pre-amp signal into a power amp with 500, 1,000, 2,000 or as many watts as you desire.

    Then you have your little doohickeys like the SansAmp Bass Driver DI, MXR M-80, Yamaha NE-1 and a bunch of others made (or at least marketed) by the likes of Fodera, Sadowsky, Raven Labs, and Aguilar. These are most useful for tone shaping, and bolstering deficiencies in an amplifier's frequency output. I like to plug my SABDDI in front of the input to my SWR Workingman's 12 to add some much-needed bottom end. Works bitchen.

    Finally, the on-board pre-amps. These are installed right in the bass and usually are powered by one or two 9-volt batteries. These give more control over your tone right at the bass. The output, however, is most likely to go into the pre-amp of your amplifier, so it doesn't take the place of your stage pre-amp.

    However, some pre-amps are good for running direct from the bass to the board. I've used the SABDDI for this, and it worked bitchen. Something like an Avalon U5 or VT-737 would work great for this, too.

    Bottom line, if you get a decent amplifier head, the pre-amp will be of sufficient quality to provide you with a lifetime of great tone. If you're a bit underpowered, or your speakers are lacking, you can add life with a small external pre-amp. An on-board (in the bass) pre-amp probably won't help a weak amp that much.

    Clear as mud, right?
  3. amper


    Dec 4, 2002
    Well, the primary duty of any amplifier is to make something louder, right? So in the interests of simplicity, we'll dispense with the power amplifer side of things, since the power amplifier, all other things being equal, is just supposed to make you sound louder in a linear fashion.

    This also dispenses with the tubes v. transistors argument, since they sound exactly the same until you push them to distortion, at which point tubes will sound very much better. The reason this is still an issue for some people is that tubes, in the early stages of distortion, sound so good that most people don't realize they actually are distorting. There are actually a few other differences, like damping factors, slew rates, etc., but these are pretty esoteric points and don't make as much of a difference to most people.

    So, aside from the power amp, a typical instrument doesn't put out a signal strong enough to drive the power amp or power section of an "integrated" amp. This is why we have preamps. The job of the preamp is to amplify the very small signal strength of your intrument to a less small level that will drive the power section.

    The term preamp, in its most basic form, really refers only to the amplification section; however, most manufacturers realize that people like to have a bit more control over their sound than that, so they add equalization stages and other effects (or effect loops) to their products. In practical usage, the term preamp has come to mean everything that comes before the power stage.

    Some enterprising manufacturers build the "preamp" section into a separate box, allowing for more versatility in your signal chain. For example:

    Like your sound, but need it louder (or softer)? Change your power amp (or its settings)
    Like your volume, but hate your sound? Change your preamp (or its controls).
    Like your volume and tone, but want to add something else? Use effects.

    Different manufacturers have thier own versions of equalization stages and effects or loops. SWR, in particular, fancies their "Aural Enhancer" (not sure if this is only eq, or some other effect). Trace Elliot has their "Pre-Shape". Lots of manufacturers build compressors into their preamps. Some people like series effects loops, some like parallel (there are good reasons for both). Almost every one has a graphic or parametric eq.

    The bottom line is, every different type of circuit has its own sound. A separate preamp section gives you the option to reorder your signal chain much easier than you can with an integrated amp. Different units might fit different situations differently....heh.

    I've got four preamps right now, not counting the ones built-in to integrated amps--a Trace Elliot V-Type, an SWR Interstellar Overdrive (on order, anyway), a Mesa/Boogie V-Twin, and an ART Tube MP. I plan on buying more...I want a JoeMeek, an ART Tube Channel, and maybe a Focusrite or two.

    As far as power amps--I have a Trace Elliot V-Type integrated tube amp, and an SWR Power 750 (also on order). I also want a Focusrite Red 5, an ART SLA-1, and a maybe a Carver PT-1800.

    All of these units have different purposes in my Grand Plan for World Domination.

    And that's just the bass stuff. You should see my guitar stuff, too...
  4. I think you understand pre-amps just fine, your having trouble understanding why anybody would need one. 1) If you want to run big power 1000 watts or more, you'll have a hard time finding a single unit (Head) with that much power. A seperate power per-amp/power-amp is the simplest way to go. 2) If you like to play around with exotic stuff, the real sh!t is in seperates. If you just want to play bass, have fun, and make money, any decent amp head will do the job. jmho
  5. thanks for the great answers, they cleared up the matter and confused me at the same time! They cleared it up because now I know that I don't need a seperate rackmounted pre-amp. Maybe somday when I have a 1000 watt setup I'll worry about getting one. I think I might get a smaller external one though just to have more tonal options. Thanks again.