Very basic question about preamps

  • Thread starter Thread starter TradCountry
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TradCountry

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Having been a home audio fanatic many years ago,and having built much of my gear at that time from kits,I know what a preamp does,but why would you need one (a separate,stand alone unit,I mean)for general recording purposes unless,of course,you were working with some sort of mic having especially low output?
Wouldn't most recording gear have enough amplification already built into the basic design of it that a preamp shouldn't be required?Or do preamps in the recording field serve purposes other than just initial amplification?
I ask this because I see preamps advertised and frequently mentioned in discussions about recording and sometimes,live performances.
Thanks,
Malcolm
 
mics are not line level like electric guitars, etc. they need amplification for the signal to be heard.
 
Yeah, all mics have "especially low output", hence the need for preamplification to get them up to line level.
 
Guitars are not actually line level, but they have more output than mics. I think TradCountry is assuming, like I am, that all mixers and audio interfaces have pre-amps built in, so why the need for another pre-amp?
 
Most mixers do have mic inputs (except for line mixers of course) but a lot of recording interfaces/soundcards don’t. And some will have a combination of mic and line inputs and so you need mic pres to use mics through the line level inputs.

Also people might like to just use better quality preamps than what they have in their mixer/interface (assuming it's possible to bypass the onboard pres).
 
Kevin Deschwazi said:
Also people might like to just use better quality preamps than what they have in their mixer/interface (assuming it's possible to bypass the onboard pres).
Click to expand...

no need to bypass them. go direct into the pre and if the pre only has one output use a cable splitter to send one to the soundcart/tape machine and one back to the desk for monitoring. If it has 2 outputs you're on easy street.

Now someone's gonna say you can't use the EQ on the board doing it that way. If you're using the right mic for the job and using proper placement then you should have no need to EQ on the way in. Putting the mic into the board only adds more noise to the signal before it hits the mic pre.
 
Right, that works for a mixer, what I said applies more for a recording interface where there's no input/output between the built in mic pre and the A-D converter.

Thanks for pointing that out.
 
OK Trad- You've gotten a bunch of answers, all of them correct. To summarize- mics (with a very few exceptions) have a much lower output than line level. In the good old days, they made a lot of high impedence mics that were made to plug into an instrument input. The switch to low impedence mics produced a better, quieter mic. So there are 2 factors involved- the output of the mic, and the impedence that it is looking for. Furthermore, most condenser mics require phantom power, which is not provided, as a rule, by power amps. That's the connectivity part of it. Preamps raise the mic level output to line level, provide phantom power, and have inputs with appropriate impedence matching for mics.

The second part is more subtle. Preamps are tone shaping devices, some more than others. Mic pres aren't supposed to make the mic sound the way it sounds. Good ones are prized because they make the mic sound *better* than it sounds. What "better" is, is a matter of opinion, which is why some people like Les Pauls and some people like Stratocasters. The color of mic pres is more subtle than guitar amps. It doesn't hit you over the head, it tickles you with a feather. Home audio amps are trying to be flat, so they can accurately reproduce all the color of the original recording. Home audio amps don't usually make good mic amps for that reason, even if the inputs can be matched to the mic. They are simply boring. Cheap mic pres tend to produce bad color, or can actually rise to the level of obnoxious distortion. The better cheap mic pres are fairly clean, because boring is better than outright distortion. The best mic pres are rarely really clean. Like an airbrushed centerfold, they're not being paid to sound *accurate* Thay're meant to sound *good*.-Richie
 
I suppose that's what they mean by a 'larger than life' sound that a good studio mic has... as well as a good preamp...like the air brushed model with implants!
 
Essentially, that's true. But "larger than life" is just one sound. Ribbon mics paired with great tube amps are famous for that sound. There are sounds I woukd describe as "smooth". Others I might call "warm". Some of the top solid state pres like my Avalon 2022 or Neve I would call "crisp" or "detailed". What sounds good is a matter of opinion. Whatever they do, the best preamps do it so it doesn't have to be obvious. A preamp is like makeup for a microphone. A guitar amp is like Kiss, a top mic preamp like Heidi Klum. So- larger than life? That's one sound you might think is good-or not. Preamps are tools, like paintbrushes. They're not just good or bad, they have personalities, and pres interact with mics. Whether it sounds good for a given application is still a matter of opinion. You may hate my idea of "perfect" sound.-Richie
 
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