Rule of thumb for setting gain

Discussion in 'Amps [BG]' started by asis, Apr 4, 2014.


  1. asis

    asis

    Joined:
    Jan 1, 2009
    I came across this video while searching what gain was.



    -Is this how you do it?
    -How do you guys approach it?
    -any good rule of thumb for setting your gain?
    I tried it on my Gallien Krueger but it was already clipping with the gain volume all the way down. Is it because i'm using an active bass?
    -what's the purpose of turning all the eq's up on the bass?

    i'm just curious on what peoples thoughts are on the subject.
    Thank you
     
  2. JimmyM

    JimmyM Supporting Member

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    That's pretty much what I do, except I don't turn up the tone controls all the way when I use an active bass. I turn them up to whatever setting I like the best. And I ignore the lights and use my ears to set the gain. If your bass is clipping with the gain all the way down, it might be because you're overcranking the preamp, but that all depends on the bass you're using and how hard you play. In that case you may want to use the active input because it brings down the level to something more controllable. But I'll tell you...in 35 years of playing professionally, 30 of which were with active pickups and preamps, I have never once needed to use an active input on an amp.
     
  3. djkool

    djkool Supporting Member

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    From what I understand, it's OK to clip the pre-amp, but not the power amp. In fact it may be useful to introduce some preamp clipping to introduce a bit of growl or distortion. It's power amp clipping that endangers your rig. I didn't see a power amp clip light on the Markbass amp (I'm not that familiar with it). It begs the question if class D amps are less sensitive to power amp clipping because they already start with a square wave?
     
  4. JimmyM

    JimmyM Supporting Member

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    Start with a square wave? A synth starts with a square wave, but amps start with the sound of your bass, no matter how they're made.

    As for power amp clipping, some are designed to sound really good with the power amp clipping, and some are not. Markbass amps are definitely not, while most tube amps and some SS amps are. Only problem is that if you're clipping the power amp section, you can be putting out twice as much wattage as the RMS wattage in peaks, which can take cabs out if you're not careful. But it has to clip at a wattage that's greater than the cabs can take in order for it to blow the cab.

    Anyway, it's all very much dependent on a particular amp's design how well it deals with power amp clipping, but having a decent set of ears and some common sense goes a long way into running your gear safely.
     
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  6. fnordlyone

    fnordlyone Supporting Member

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    As one who has sucked upon Jimmy's teat of knowledge; and as a scientist who believes only through experiment…
    dead on true IME everything the hardest working bobble head in TB said, da legend Jimmy M! :cool:

    fnord!
     
  7. bluesdogblues

    bluesdogblues

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    -Yes
    -to have the most gain of the bass.
    -As much gain I can get, as before it clips, just like the video, but sometime along the performance the clip light might flashes a bit, it's OK for me, I trust my ears.
    -EQ is just a tool, some uses it like an effect, I use it to 'correct' some frequency that I feel not right because of the influenced of the different environment (room etc), or the need of the context of the song, I don't like EQ much esp in 'increasing' except that I really have to, I prefer 'decreasing' some frequency needed to, and I always do it as little as I could, I'd like it to be as flat as possible,..different person different needs. I read that Chris Squire always turn up the Treble and turn down the Bass as his EQ setup CMIIW.

    I never play active bass nor Mark Bass amp tho.
     
  8. Jbassrockboy

    Jbassrockboy

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    I use a momark head and a passive j bass and p bass

    I find I can set the gain very high depending on how low I set the individual eq

    If I run eq's on flat out the clipping kicks in earlier

    To set the gain based on one eq setting on a markbass head does not translate to an outcome where clipping will always occur at that same gain level with different eq settings

    Not having an active bass I imagine the eq levels or other sound shaping options would likely need to be wound back on both the bass and head in an attempt to get a higher level of gain without clipping

    Another issue within TB is a lot of people recommend find your sound and set and forget I.e set the head flat

    I use to be like that until I realised that by just using one setting I was missing out on a whole range of tone options

    Amp heads generally have several knobs and in better gear they usually provide a change in tone, one way or another

    It's true that a lot of twiddling can bring unwanted results but without experimenting and trying different combinations between the bass and amp there is a limited range which quite often can be boring , bland or just out of kilter with the room environment

    Just some thoughts, be bold in trying different combinations and as jimmy says use your ears but also watch that little clip light

    It is there for a reason and there is no need to damage valuable equipment by ignoring it

    In short, yes the clipping is related to the gain but definitely on momark the clipping is very sensitive to eq..

    Rossa
     
  9. LeonD

    LeonD Supporting Member

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    The video was mostly correct but did have some errors. The point here is to find the place where you'll have the lowest amount of noise from the preamp without distorting it. Below is per the SWR manual.

    Don't just turn your basses eq all the way up. Set it for the loudest passage you'll be playing. How ever you have the eq on the bass, eq on the amp (with some amps, this will effect the gain), volume on the bass and effects (if they are before the amp), set them that way. Now while playing, slowly turn up the preamp volume/gain up the amp. Keep tuning the gain up until it start to flicker on. Then turn it down a smidge. This will give you the best signal to noise ratio with any distortion.

    If you want some grind from the preamp, turn the gain up till the light stays on. Although, a lot of preamps are designed to add warmth from the tube and not grit. You be better off using a pedal for that.

    On a final note if you can't get the light to not come on, try using the active input. Note this has nothing to do with if your bass is active or passive, it how hot a signal your bass puts our or how much eq you're using. My hottest bass by far is a passive P.
     
  10. djkool

    djkool Supporting Member

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    Class D amps convert the sinusoidal waveform from your bass into a square wave so it can then be amplified and converted back into a louder sinusoidal waveform. Conversion to the square wave provides greater efficiency. Clipped sinusoidal waves approximate square waves. Clipping in the power amp can force a speaker to have it's voice coil heat up because the motion of the cone is no longer smooth. Just as a square wave isn't a smoothly transitioning waveform like a sinusoidal waveform.

    I'm just curious if a class D power amp can handle clipped input signals better because they are already designed to handle square wave signals.

    No argument that avoiding audible distortion is preferred. However, is is possible that an inaudible condition could still damage speakers? You can't hear the voice coils cooking unless the speaker is experiencing over-excursion.

    BTW, I'm an ME, not an EE, so if someone wants to correct my understanding of a class D amp, I won't be offended. Just got me thinking. Not looking for an argument.
     
  11. Sartori

    Sartori

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    -No.
    -I turn the knobs until I get a sound I like. My current amp doesn't have a true gain knob per se. I usually run the bass channel volume at about 4-6 though. It doesn't have a clip light. On my old head, which did have a gain knob, I usually had it about half way, so the clip light was coming on like every note at least at the beginning of the note. It was an Ampeg, though, and on those the light really just means "you now have enough gain."
    -When you're done setting your gain, it should be both loud enough and sound good. That's pretty much the only thing that matters. You may be sending the amp a really hot signal due to the active bass.
    -I suppose the purpose might be to give the amp the maximum amount of signal from the bass that it's going to get while you're playing. I don't really know, as I don't have any active basses.
     
  12. lowfreq33

    lowfreq33

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    I think you've kind of got the wrong idea about Class D. The power SUPPLY in a class D amp is the difference between it and a traditional solid state amp. The signal path is no different. At no point is anything converted to a square wave.
     
  13. djkool

    djkool Supporting Member

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    Got it. The power supply, not the signal path. Thanks for the clarification.
     
  14. Joe Louvar

    Joe Louvar

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    I simply close my eyes and while listening I turn the knobs to where they sound best without the cab farting out.
     
  15. Jbassrockboy

    Jbassrockboy

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    Not scientific but that pretty well sums it up from the perspective of playing...
     
  16. ga_edwards

    ga_edwards

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    If the clipping light comes on with the gain control right down, it sounds like the bass has a really hot output.

    The advantage of active basses versus passive is that you can turn down the basses volume control without affecting tone. It might seem counter intuitive, but there is no need to run an active bass flat out. Passive yes, active no.

    Turn the volume of your bass down, and perhaps adjust the onboard eq so it's not cranked. You should be able to get to a point where you gain adjust the gain on the amp so that you can avoid clipping but keep noise down.
     
  17. Salamenster

    Salamenster

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    When playing with a pick, I take it even further by putting a limiter pedal in front of it, in front of wich I put a EQ with a HUGE volume boost (and in my case a slight treble boost). The limiter cuts it off all at EXACTLY the same level, so no harsh peaks, so higher gain without clipping because of peaks and a nice even rounded picktone.
     
  18. dincz

    dincz

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    Because EQ controls are also gain controls - but they only affect gain over a limited range of frequencies. Gain and EQs at max gives you the highest signal level your bass is capable of - worst case.

    No they don't. They use the audio signal to modulate the pulse width of a separately generated square wave. That square wave keeps running even when you stop playing.

    You're confusing power amps and power supplies here. Both class D and traditional solid state amps can run off any kind of power supply - line/frequency/transformer type or switch mode type. The power supply is the difference between a light amp and a heavy amp.
     
  19. gleneg61

    gleneg61

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    Jan 10, 2008
    As I don't like or want any grit, overdrive or distortion in my sound, I dial the master full open & use the gain as my main volume adjuster, thereby avoiding clipping altogether. If I use a back line with only a gain knob, I knock back the bass a bit on the eq for the same perceived clean effect. Of course nowadays, I'd always have my GK or GB head in my gigbag anyway so I'm in control regardless. My 2c!
     
  20. inri222

    inri222

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    This is how I do it. I do not use any grit, overdrive or distortion from the amp. I use a SansAmp BDDI for that so I want a clean amp sound.
     
  21. LeonD

    LeonD Supporting Member

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    That's a fine way to do it. You just might be getting a lower signal to noise ratio (i.e. more noise) that way.

    Depending on other circumstances, it might not be an issue.
     

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