1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  
    TalkBass.com has been uniting the low end since 1998.  Join us! :)

Amp EQ settings

Discussion in 'Amps and Cabs [BG]' started by ironjohn, Nov 24, 2013.

  1. ironjohn


    Jun 1, 2013
    Chicago area
    As I understand it basic combo amp EQ, bass-mid-treble, knobs are just variable resistors, my question is:

    Shouldn't all 3 be turned up full as a starting position to get the full signal coming through, and then backed down to cut off whatever frequencies I don't want? Same idea as the "tone" knob on the bass, start with full on, then back off.

  2. Not necessarily true, Fender style tone stacks as an example are boost bass and treble (2 out of 10 is "flat") and cut only on mids (10/10 "flat").
  3. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Hey, if it works for you, that's cool.
  4. Bassist4Eris

    Bassist4Eris Frat-Pack Sympathizer

    Gain structure: a scary-sounding term that actually means something quite simple, namely, every step in your signal chain puts out a certain amount of signal, which must then be handled by the next step. And the next step will behave best when being hit with neither too little nor too much signal. I would bet that if you tried turning your EQ knobs all the way up, your tone would suffer due to the power amp being hit with higher-than-optimum signal. But hey, it's worth a try.
  5. Good point on avoiding crazy overdrive. Otherwise, where you start doesn't much matter.

    It is always interesting to find the nominally flat positions on TB and see if you agree with the amount of baked in midscooping commonly found at noon positions.
  6. ironjohn


    Jun 1, 2013
    Chicago area
    Thanks for the comments guys.
    I'm pretty new at this and really trying to hear what I'm playing flat. I'm guessing "Noon" on the EQ knobs and full on the bass "tone" is the best flat starting point?
  7. ArtechnikA

    ArtechnikA I endorsed a check once... Gold Supporting Member

    Feb 24, 2013
    As previously stated - without knowing what amp, there is no way to guess.

    (I'd guess the answer is in your amp's manual...)

    If it uses the "Fender style" EQ, 'flat' is 2-10-2.
    Not just Fender uses this model...

    On some, all-numbers-equal is flat. There are other models.

    Tell us what you've got, and someone here will know how to make it flat...
  8. ironjohn


    Jun 1, 2013
    Chicago area
    I have a simple Fender Rumble 30. I didn't see anything in the very limited manual about flat settings, e.g., 2-10-2.
  9. Zoa


    Dec 28, 2009
    It really depends on the individual amp.
  10. ArtechnikA

    ArtechnikA I endorsed a check once... Gold Supporting Member

    Feb 24, 2013
    I had a look - you're right - it doesn't.
    It -does- mention full power rated with EQ flat, and the individual controls are described as being ±15dB.

    So it does give the impression that "center" is 0, and that all at center would be a good starting point for what they think is flat.
  11. I didn't find a flat setting either but it is an active EQ so with all tone controls full up you would have a 15db boost (over flat) at 60Hz, 630Hz and 6KHz. Far from a good "starting point". ;)
  12. ironjohn


    Jun 1, 2013
    Chicago area
    Wow, thanks a lot guys. You've been a big help.

  13. ironjohn


    Jun 1, 2013
    Chicago area
    One last thing.
    I'm I correct about the bass "tone" knob?
    Turning it up, just bleeds off high frequencies away from flat?

  14. Fuzzbass

    Fuzzbass P5 with overdrive Supporting Member

    The tone knob on a passive bass (traditional Fender bass, no battery) is also passive: there is no boost, it cuts higher frequencies only. In that case, the flattest tone is with the tone all the way up, just as you said.

    However very few amp EQs are passive. Most are "active", that is, they can cut and boost. So, for flattest response you don't want cut or boost.

    With most amps, flat is at noon, but as noted above, this is not always true.
  15. ArtechnikA

    ArtechnikA I endorsed a check once... Gold Supporting Member

    Feb 24, 2013
    On mine, CW is more treble, CCW is less.
  16. If you mean 'up' as in counterclockwise, yes. It just bleeds highs to ground.
    The problem with your previous inquiry is that you'd create three large bumps in your frequency response. It wouldn't bring 'everything' up. Just three relatively narrow areas.
  17. That is why a good many of us come here. :)
  18. will33


    May 22, 2006
    On the bass, the further you turn it down, the more treble it bleeds off,. Most amps other than little practice amps that only have one tone knob, usually don't work like that. At least the bass and treble knobs, and often the mid too, can add rather than just subtract from the sound. On a lot of them, having the bass full up usually means more bass than the speaker can handle.

    Long and short of it is, just adjust things to where it sounds good while listening to the speaker for signs of distortion or stress. If it distorts, turn down the bass, the volume, or a bit of both.
  19. Noon starting off point can't go wrong.

    Most any amp will go a lot louder before distortion if the bass knob is only adjusted downwards.
  20. Steve Dallman

    Steve Dallman Supporting Member

    The Fender tone stack is a passive circuit that has an inherent mid cut. The controls are very interactive, meaning, changing one control will change the way the other controls work. All controls at 10 will let the most signal through, but it will not be "flat." As others have said, the closest you can get to "flat" with a Fender tone stack is with the mid cranked, and the bass and treble seriously cut...2-10-2. Turn all the tone controls down on a three band Fender EQ and there will be no signal.

    Ampeg EQ is different. The bass and treble use a passive Baxandall tone stack that acts like an active, cut and boost EQ. Center is flat, and the controls are not interactive. The mid is an active, boost and cut circuit using an inductor based circuit. Center is flat.

    Some amps are variations of a Fender stack, like Hiwatt and others. Many are all active EQ's. The EQ design has a major effect on the signature tone of an amp.

    So with some amps, "flat" is with the controls at center. Others take some knowledge of the passive design to achieve a "flat" tone. Even though a Fender has an inherent mid cut, it sounds great and is a tone we all know and love...at least for guitar. Marshall and Vox have very similar tone controls to Fenders, but with the mid cuts in different places and the tone controls let different frequencies through.

    Some Fender type tone controls have only bass and treble. The midrange is actually preset to around 6-7...the blackface Bassman for instance. The closest to "flat" is with the bass and treble turned all the way down...and it doesn't sound very good set that way.

    With a two band, baxandall circuit, as on an Ampeg B-15, center is "flat." There is no mid control, but if you turn the bass and treble up, the mids remain "flat" so the result is a "mid cut." If you want a mid boost with a Baxandall circuit, you turn the bass and treble down. The mids remain at center so it sounds like the mids are boosted. (the volume will have to be reset to make up for the volume loss due to the bass and treble being turned down.)

    The circuits are varied. The passive ones use caps to pass or shunt frequencies with resistors to control the "shape" and response of the circuits. Active circuits commonly use gain stages with the caps in sort of a gain feedback loop of gain setting action of the gain stage.

    Not just simple "resistors" but various circuits using multiple caps, resistors, sometimes inductors, transistors, op amps, tube stages, potentiometers, etc. The placement of the EQ circuit in the gain staging of a preamp matters as well. The first Fender Bassmans use a lossy passive tone stack. There are preamp gain stages to raise the signal so the loss is compensated for. The first Bassmans put the compensating gain stages all BEFORE the tone stack. The multiple stages before the tone stack created a preamp that had little headroom and easily distorted...not great for bass but guitar players loved it.

    Later Bassmans changed the gain staging. The had an initial preamp stage, the lossy tone stack, and put a recovery gain stage just after the lossy tone stack. The volume control was also placed between the gain stages.

    This gave the preamp much more headroom, and Fender used this type of tone stack in blackface, brownface, and silverface amps and still use it today. Unfortunately, Fenders power amps were usually not large enough for bass players of the day, compared to the bass giants like the SVT, Acoustic 370, the big Sunn's, etc.