A Straight Answer for A Straight Question!!!

Discussion in 'Microphones (live or studio)' started by DandalphTheGreat, Feb 15, 2006.

  1. What the hell do preamps and compressors do?

    Please help me because i ask the question and people beat around the bush, BS'in me because they don't fully understand it themselves..

    What I need to know is:

    1) The benefit of their usage.
    2) When to use them.
    3) How to apply them to guitars, basses, and drums.
    4) What is the differnace between the built recorder compressors on a Yamaha AW16G and a $200 rack Compressor/Preamp

    any REAL help is fully appreciated
  2. RemyRAD

    RemyRAD Member

    Sep 26, 2005
    1) Preamplifiers when referred to within recording.org, generally referred to anything that can boost the level of the very small voltage coming-out of microphones to higher line level voltages.

    2) You need to use preamplifiers where ever you are using microphones and/or items like acoustic guitar with pickups, etc..

    3) You applied them by plugging in your microphones to put on your drum set. Plugging in a dynamic mike such as a Shure SM57 up to this beaker on your cabinet. By taking a direct box or DI for your bass into the preamplifier to boost the level that is approximately 50 DB higher than it was to begin with.

    4) In response to this last question, I'm not really familiar with that Yamaha unit. Yamaha has made some nice devices in past years. Although not well known for any compressors or limiters they are very well-known for their musical instruments, pianos, digital effects devices, PA mixers and motorcycles. What else can I say? Other manufacturers make similar equipment but many other manufacturers are better known for things like compressors/limiters, in comparison to Yamaha. There is no one best choice. It's like buying a car. Does it have the features or functionality that you're looking for? Can you take it for a test drive? Doesn't have good longevity? Doesn't hold its value? Will it cost you your firstborn male child??

    Suffice it to say they do not make junk. So whatever you're thinking of its probably not a bad choice?

    I drive a Honda motorcycle but I would consider a Yamaha next time.
    I own a Yamaha C3 grand piano and a couple of old SPX90II and love them all.

    Go for it!
    Ms. Remy Ann David
  3. Cucco

    Cucco Distinguished Member

    Mar 8, 2004
    Tacoma, WA
    Okay, when you put it like that, I'm assuming you want a simple explanation. I'm going to oversimplify in some cases here - I don't want to talk over your head and make your confusion worse. If I'm not clear, let me know.

    Simply put, the voltage that your microphone puts out (which, just like a speaker - another version of a "transducer" - converts energy types. In the case of microphones and speakers, its a matter of converting vibrations into voltage and vice-versa) is not enough to give you adequate signal or amplitude in your mix. In fact, many mics need a LOT of help.

    This is where the preamp comes in. This should really be called a signal amplifier, not a preamp - as a true preamp's goals are often slightly different than what a microphone preamp's are (preamps, by definition, attenuate sound from a given level - a microphone preamp amplifies sound then attenuates it with the knob on the front marked gain...this is not ALWAYS the case, but again, simple...)

    Most preamps also provide phantom powering (a 48 volt DC current to charge the backplate of most condenser microphones) so that you can use a condenser microphone. Of course, phantom is not required for dynamic (shure SM58 and the likes) and ribbon microphones. (Can be fatal to ribbon microphones - POP!)

    Mixers and many pro-audio sound cards include microphone preamplifiers, but all preamps vary in quality. The best preamps are typically those that are designed to be nothing but a preamp - no fancy signal processing, no mixing console attached to it (yeah, yeah, there are SSLs and Euphonic's and API's......blah, blah, blah...). As is the case with many things pro-audio - you quite often get what you pay for with a preamp. There are a few pleasant inexpensive surprises (like GT's Brick and Summit's 2BA-221). But, there are many disappointments (such as anything that starts with "Behr" and ends in "Inger.")

    Well, let's see - an entire book or more could be written on the usage of compressors. To state it simply, a compressor is a device whose intended purpose in life is to decrease the dynamic range of your mix. In other words, it will make it so that the loudest parts of your mix and the softest parts of your mix are much closer together. It doesn't just get used on whole mixes though. (More on that in a minute).

    How a compressor works -

    Signal is fed into the compressor by means of a cable. You have many potential settings to tweak on that signal. Let's start with the logical ones:

    Usually shown in -xxdB format. Simply put, this is where you want your compressor to start working. The lower the number (remember, -15 is lower than -5), the more compression you will be working with. This is not always a good thing - as most compression is done sparingly.

    Pretty simple. It is expressed in the following way "x:1" X may be any number, but often you'll see numbers ranging from 1-10. What this control means is that for every 'X' decibel(s) your signal rises above the threshold (which you've already set), the compressor will only allow the unit to rise 1 dB. So, for a real world example:
    If you set your threshold at -15dB and the ratio at 4:1 (rather aggresive) and the original signal now peaks at -11 dB - there is, in the original signal, a 4 dB increase. However, the compressor will only allow that signal to increase 1dB, hence raising your level to -14dB.

    Attack and Release times:
    This simply tells the compressor how quickly (or slowly) to make the change. Quick times will catch fast transients such as 'S' sounds (sometimes), snare drum hits, etc. The release time tells the compressor how long to hold on to the compression before it lets go. If you are too short, the compressor will "pump" a lot - meaning you will hear wierd volume changes at inappropriate times in the mix. If you let it hold too long, you run the risk of creating mud.

    The settings on the Attack and Release times are expressed in milliseconds (1/1000ths of a second - ms). Fast attack times are generally between 1 ms and 25 ms. Beyond that, you begin to get a little slower. (Slow attacks can be good - it allows the first sound through but clamps down on the rest of the signal. This is a good technique to help drums sound more dynamic sometimes.)

    You will hear MANY formulas on how to figure release times, but the best thing to do is simply listen. Keep pushing it back until the pumping and breathing stop and no further.

    Gain (often referred to as "Output" or Make-up Gain)

    Now that you've effectively "squashed" your recording down, you've essentially made the instrument or track quieter (by lowering your loudest levels). You can turn up the makeup gain so that your loudest levels are the same as they were before, this will bring up your lower levels now.

    Watch your meters. If you're only reducing 3dB but you're boosting 15, there's a problem... Generally you should boost the gain only as much as you're cutting. (This rule can be broken, but for specific reasons only).

    Well, a mic pre doesn't have "benefits" per se. It's simply a necessity. If you don't have a mic preamp, you aren't getting signal (or at least not enough to work with...)

    As for a compressor - a well-utilized compressor can make a mix gel and let instruments work beautifully together. However, a bad job of compression (which is VERY easy to do) will undoubtedly RUIN a recording. Period. It took me no less than 8 years of practice to get halfway decent at compression. During those 8 years, many of my mixes SUCKED because I just didn't know how to do it right.

    Well, I think I hit on the compressor enough...
    As for the mic pre - turn up the gain until the mic is loud enough but not so loud that you see red lights all over the place. In the digital world, it's far easier to increase the volume later than to fix the repercussions of "too much gain."
    Another whole book. Seriously. The mic pre, by now, should be a "No DUH" scenario. Turn it up until you can hear the drums, guitar or cricket farts - whatever you happen to be recording. (Cricket farts require a lot of gain BTW).

    The best thing I can tell you is:
    Study physics
    Get a compressor like the dbx266xl. It's cheap and has all the controls that I discussed above. Plus it doesn't sound all that bad.
    Practice using the compressor
    Not much. Both of them excell at sucking hard.

    First, if you're looking at a $200 compressor/preamp combo....don't. Nothing selling for $200 that has both a comp and a pre is worth a damn. A GOOD compressor will set you back about a grand or so (there are exceptions, such as FMR's RNC).

    Good preamps will set you back about a minimum of $400 - $500 per channel. Much below that and you're really not getting an upgrade from the stock pres in your Yamaha AW16G.

    Well, any real donations to my carpal tunnel repair surgery would be helpful too... :roll:

    Seriously though - I hope some of thes has been helpful. If not, I would say, avoid messing with recording and leave it to the pros. There's a reason why this stuff is hard - not everyone's supposed to do it.

  4. Cucco

    Cucco Distinguished Member

    Mar 8, 2004
    Tacoma, WA
    Ahh Remy - I see we were typing at the same time... :D
    Insomniacs of the world unite!!!
    (Dyslexics of the world untie!)

    BTW - original poster (whose name is too long to remember and I'm too lazy to scroll down to see it and then retype it, but obviously not too lazy or I wouldn't be writing this here disertation on my laziness...) - check out the topic at the top of this forum entitled "Yet another question about compression." Senor Shotgun gives a very good and colorful explanation of the purpose, and how it's done.

    BTW - Remy - I've been looking at getting a Yamaha bike too!!! You can hop in the HOV with it, it gets great gas mileage and chics dig it!!!

    Although I'm looking at their smallest bike (the Virago 750.) I'm a small dude though, so I don't need THAT much power between my legs - besides, I'm Italian, I already have plenty of power there..... :shock:

    :D J
  5. RemyRAD

    RemyRAD Member

    Sep 26, 2005
    Well Jeremy, I am a fat woman and I love my 500 cc Silver Wing from 1982 that I purchased new! It has more than enough power for me. I rode a 750 CC magna once and tough a wheelie right off, it was much too powerful! Oooooopppsss, now I'm dating myself. Probably the best date I've had in a while!?!? Motorcycles! The best way to beat the HOV debacle! Be careful, you have a lovely family to support and if you're not 360° eyes, you'll get hurt! I thought I was going to be killed a few times but for some reason, God doesn't want me yet! It will also destroy your hearing even with a good helmet. That is why I'm still an audio engineer, so I can withstand high SPLs, it takes many miles of riding to be a good audio engineer.

    Recklessly devoted
    Ms. Remy Ann David

    Yes I am an insomniac of the worst order. Thankfully I don't have to be at Voice Of America until noon on Thursday so I can sleep late. Not too late. Besides it's all low-quality TV sound.
  6. Wow that was a much better response than i had expected.

    Thanks a lot for the help, I really appreciated it.
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