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Amp EQ revisited

Discussion in 'Amps and Cabs [BG]' started by manchild, May 22, 2012.


  1. manchild

    manchild

    Jan 30, 2008
    Greetings all,

    I have been reading through the stickies in the amp section, in particular amp eq boosting vs cutting. it would seem from the info that cutting gives 'colouration' as well as boosting (although less so). Also i can appreciate that getting rid of troublesome eq points instead of tweaking the ones you want to hear more of, will give you a broader sound.

    My question is about the db and 'gain stage' boost point.

    If you boost eq you will need to adjust (cut) volume to compensate surely? Ie boost low mids by 3db then lower volume by 3db equals same output as before?

    Can someone explain the physics of this i don't get it and sure that other newbies to this sort of thing could do with some clarification as well as me.

    Cheers
     
  2. BurningSkies

    BurningSkies CRAZY BALDHEAD Supporting Member

    Feb 20, 2005
    Syracuse NY
    Endorsing artist: Dingwall Guitars
    Not necessarily. Remember, that you're only reducing one band, but when you're increasing overall gain, you're raising ALL the bands universally... And vice versa for increasing the level of specific bands.

    Your best bet is to ignore the 'Db's and use your ears. Are you having headroom problems?
     
  3. 1958Bassman

    1958Bassman

    Oct 20, 2007
    Boosting EQ controls decreases headroom in that range and adds noise. The signal can't be boosted infinitely and at some point, the power supply's limitations come into play.
     
  4. Freight Train

    Freight Train Earth-based Alternative Scientist, Sex Researcher

    Feb 25, 2012
    Dallas, Texas
    First, BurnginSkies is correct that you should use your ears as the final determining factor, regardless of what 'the book' says.
    Speaking as a recording and mastering engineer of now 38 years experience, and bassist for nearly 47 years, here's a few points about eq:
    First, don't feel obligated to use eq just because your amp or preamp or stomp box or whatever has it. If you have a good bass and a good rig, you really shouldn't have to use much eq at all. Also, eq can be very deceiving. It may appear as you're adjusting that you are gaining clarity. But any eq, even the best, will add phase distortion, mostly when you boost, that affects and clouds frequencies other than what you are adjusting. Any experienced recording engineer has learned this; the less eq you use on a track, the more it will sit tightly and clearly in the mix. An experienced engineer will use mic selection and mic placement to get the sound he wants, and hopefully use no eq at all. Same is true of your bass - if you have a good bass, and you've selected a rig that delivers the sound you want with little or no eq, you are going to be more solid and present in the mix.
    Second, you generally do get less phase distortion when you cut rather than boost, so for example if you want more mids, try cutting low's and high's and then raising the overall volume instead of boosting mids.
    Third, regarding your question about levels, any good analog chain will have plenty of headroom, assuming you have things gain-staged properly, to be unaffected by any boosting you're doing with the eq. Assuming of course that you're not doing crazy boosting. Getting back to what I said about using little eq, if you're having to boost or cut much more than a couple of dB, maybe 3dB, at any one frequency, you don't have an eq issue, it's a bass or a rig issue, or both. And no matter how good the eq is - I've got stereo EQ's in my mastering room that are upwards of $8k - they all turn to **** once you go much beyond 3dB of boost or cut. As someone pointed out you always have to be aware of noise, especially when you're boosting, but if you're in the analog domain the level shouldn't be an issue, except if you are recording then you need to re-check your levels after you've eq'd.
    However, level is a real issue if you are in the digital domain, especially in recording. The mistake that almost every aspiring recordist makes is they max out the digital scale on every track they record, leaving no headroom. So if your bass track is slamming up to 0dB full scale, then absolutely you have to lower its level before you boost OR cut with any eq. This is an important thing that so many people miss. To many it's obvious that if you're boosting you're going to exceed 0dB full scale, but they don't realize that when you cut you create anomalies, akin to the phase distortion I mentioned, that will cause peaks that will spike a dB or more over the level of the track. The problem with having to lower the level of the track before you eq is that you are having to use another DSP step (Digital Signal Processing) in order to lower the level, and every DSP process you add to a track will cause you to lose clarity. All could be avoided if the engineer would just cut the tracks with at least 3dB, preferably 6dB or more, headroom below 0 full scale.
    So, if you have a bass rig with a digital preamp, it's important to know the level your bass is hitting prior to the DSP, because if you're pushing or at 0dBfs, any signal processing you do, eq or otherwise, is going to cause distortion.
    All of this is totally contradictory to what the equipment manufactures, reps and sales people want you to believe - it's in their best interest that you think that there's no way you could possibly get a professional sound live or in the the studio without having effect stacked on effect, when most often the exact opposite is true.
     
  5. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    I think Freight Train's post was excellent when it comes to EQing for recording and running the PA. When it comes to bass amps, though, I say move those knobs anywhere you feel like it and don't worry about it if you're boosting. As long as you like the sound you're getting, it's all good. I used to never worry about knob positions for the longest time, and then I got introduced to the concept of not boosting in the mid-90's, and quite honestly, I think my sound suffered for it, and it took me longer to get a sound that I could tolerate. Once I decided to free myself of that limitation, I think my sound greatly improved.
     
  6. Freight Train

    Freight Train Earth-based Alternative Scientist, Sex Researcher

    Feb 25, 2012
    Dallas, Texas
    Good point JImmy, and if you look at my post that's what I said first - do what your ears tell you is good, and don't worry about if it's the 'correct' way. But also, I'll stick to this point 'til my death, because I've learned it over nearly 40 years of making my living in music production, not as a hobbiest, that the less eq or fx you use, the better your signal will be. Don't be afraid to use it if you need it, but be sure you need it. You should know where the 'flat' setting is, and work from there, and you'll wind up using less eq than if you just start cranking knobs.
     
  7. Korladis

    Korladis Inactive

    Just use your ears. I only boost, because that overdrives things a bit more, which is what I want.

    If you want headroom, try to cut what you don't want, or if you want something boosted, boost it only a little bit and cut everything else a little bit. Or boost it and then cut your overall volume.

    Of course, I don't care about headroom, so I completely disregard the advice I just gave. There are no real rules as far as EQing if you like the sound you're getting and it sounds good with the band.
     
  8. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Dig. Might change the word "better" to "cleaner," but that's nitpicking. When you're recording or running sound, you absolutely want your source material to be reproduced cleanly *, even if the bass amp is turned up to 11 and the bass knob is cranked, so that is actually better in that circumstance.

    * Tape saturation can be cool as an effect, though ;)
     
  9. R Baer

    R Baer Supporting Member Commercial User

    Jun 5, 2008
    President, Baer Amplification
    Agree, with one exception that careful consideration be given to one's use of the BASS control. Pretty much every amp out there is using a shelving type bass control, which boost everything below the EQ center equally. Heavy boosting of these lowest frequencies puts an increased demand on your cabinet's drivers, pushing them into over-excursion sooner. Even though many amps employ a high pass filter of some sort (many don't), heavy use of bass boost, whether on your amp, or on your bass, is usually not your best option, especially at higher volumes.

    I typically start with my EQ flat and then if I find the sound a little bright, or thin, I roll back the tone knob on my bass, or TREBLE control on the amp first. Then, if I feel I need to beef up the sound a bit, I try boosting a bit of low end around 100Hz, providing I'm using an amp with that much EQ control. If I still need a little fatten sound some more, I will then reach for the BASS knob, usually on my bass. Here, I like to go as little as possible to just add some weight to the notes. As a general rule of thumb, as the amp's volume goes up, the amount of bass boost should go down.
     
  10. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Good stuff as always, Roger!
     
  11. TNCreature

    TNCreature Jinkies! Supporting Member

    Jan 25, 2010
    Philadelphia Burbs
    Cool post, y'all.
     
  12. manchild

    manchild

    Jan 30, 2008
    Thanks for all the replies. some good info to go on ;)
     
  13. AstroSonic

    AstroSonic Supporting Member

    Dec 10, 2009
    rural New Mexico
    The acoustics in recording studios are on the average a good deal better than in many (most?) performing venues. As a result, a little more knob turning may be needed than is suggested above.

    Overall this thread has brought out some great information and valid points of view.

    Bob
     
  14. manchild

    manchild

    Jan 30, 2008
    By the way. if cutting bass and treble gives the perceived sound of boosting mids, does cutting low mids give the effect of of boosting high mids?

    For example if i was to cut around 250hz would you hear more of the 600hz to 3khz range?
     
  15. Korladis

    Korladis Inactive

    No, it gives the perceived effect of boosting everything but low mids.
     
  16. manchild

    manchild

    Jan 30, 2008
    It wouldn't give a 'scooped' sound in the same way that cutting 500hz would though would it?
     
  17. bongomania

    bongomania Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    It would be a different scooped sound.
     

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