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Tube amp natural distortion?

Discussion in 'Amps and Cabs [BG]' started by mebusdriver, Mar 6, 2003.


  1. In another thread people were mentioning that when clipping with a tube amp the bass sound comes out like overdrive. I have no idea how to achieve this sound can some one explain it for me? And do you mean overdrive like a distortion pedal or overdrive like some growl on the low end? I believe this is the sound I have been trying to get so I really need help. Also I have an SWR 4004, is this effect possible with solid state? When I clip I just get the farting noise.
     
  2. Tube overdrive or distortion is similar to that farting noise you hear with your solid state amp, but tubes fart in a good way. :D It smells like roses.

    Seriously though, overdriving tubes is the same phenomenon as overdriving transistors, but tube overdrive sounds different from transistor overdrive. Tube overdrive is more "melodious" or "harmonious" if you want to try to put it into words. A little bit of tube overdrive tends to fatten up the sound without sounding like a fuzz pedal.

    Head down to Guitar center and try out some different amps. Find one with at least a tube preamp and play while turning up the Pre-Gain. You'll hear the effects of overdriving the preamp tube. It will sound distorted, but not quite as farty at first like a total solid state does when overdriven hard.

    Chris
     
  3. rickbass

    rickbass Supporting Member

    Just adding on to what Chris says, (hell, he's forgotten more than I know about amps).

    But one thing that brought the concept home to me was seeing how the different technologies clip.

    If you look at the top of sine/wavelengths for a tube amp that is clipping, they are flattened out. It produces a "sweet" sound.

    A solid state unit produces sine/wavelengths that look like pointy, sharp spikes when it clips. They sound harsh and nasty.

    Something like a SansAmp Bass Driver prides itself on emulating/imitating the "soft clipping" of a tube amp. I'm not saying that unit is a perfect substitute for an all-tube amp, but it certainly gets you closer.
     
  4. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    Tube power amps tend to clip gradually; if you look at a tube amp output with a sine wave as a test signal and you increase the signal level, at a certain point, the peaks of the sine wave will start to squash down, but it'll take a lot more signal before the peaks actually flatten out (at which point it'll start sounding bad). If the sine wave starts squashing on one side--negative or positive--before the other, it'll actually sound better than if the squashing is symmetrical because there will be more even-order harmonics in the resulting distortion.

    Solid state power amps tend to clip abruptly; if you did the same test on a solid state amp, you'll see the sine wave reach a point where the positive and negative tips of the sine wave start to flatten out, and if you increase the signal further, you'll see that the signal just flat-tops on the + and - peaks.

    In either case, major flat-topping causes farting sounds.

    IMHO, the most versatile way to get a good overdrive sound is to have either a preamp or a pedal that creates the sound, and a clean power amp after that. This way, you're not locked into running the amp at near-full power to get the sound.
     
  5. Alexander

    Alexander

    Aug 13, 2001
    Seattle, WA
    I agree - I got best tone the other night out of my SABDDI by turning up the drive. The volume was only noticably louder, but the smooth overdriven sound was there. It cuts through like nothing else.