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Fender Bassman 70... more breakup.

Discussion in 'Amps and Cabs [BG]' started by powellmacaque, Nov 11, 2010.

  1. So I may be purchasing a Bassman 70 with a matching 2x15 for a pretty good price from my school. Yes, I know these are the stepchildren of the Bassman badge, but I like the way this one sounds. It need some looking at by a good amp tech and I think it'd be an amazing sounding amp.

    I've played the amp a bit and I have been able to get it to give me a bit of grit when crossing the channels over, but not much. I know this amp is known for being super clean, and I do like that, but I was wondering (since I'm a tube newbie) if I could increase the "gain" by changing the tubes out? If so, what tubes are recommended? Are there any other tricks for making this amp a bit dirtier? I have some nice pedals, so getting it to break up more isn't necessary, but it'd be nice.

    I'd be using this amp for bass, baritone, and guitar so I'd like to keep it pretty versatile.
  2. will33


    May 22, 2006
    If you've jumped the channels and cranked everything labeled volume, that's as dirty as it's going to get. Changing preamp tubes may change the tone or character a little bit but if it already has ax7's in it, you're not going to get any more gain. Use pedals.
  3. I've cranked the bass side to 10 and the guitar side to about 9 (if I go all the way to 10 I get a high-pitch squeal which I assume can be fixed by a good amp tech). I've never cranked the master, this thing rumbles the room at about 6 so I may need to get an attenuator to get it all cranked.
  4. Tusec


    Jan 10, 2010
    I can't remember if the Bassman 70 has two or three gain stages in the Bass channel preamp. The earlier BF/SF Bassmans had three but they switched to two later. If yours has three, there are some extremely simple mods to get more crunch (Fender throttled the third stage way back to keep things clean but you can undo what they did). If it only has two, it's pretty much a clean machine and there's not much you can do about it besides cranking up the master volume to get the output section to distort. Replacing the 12AT7 in the phase inverter position with a 12AX7 will give you more output section distortion but again that's only with the master volume turned up. Also, I suspect that the stock speakers will probably start distorting before the amp distorts, which will give kind of a muddy, flappy distortion that you might or might not like. The simplest approach might be to just keep the amp clean and use a good bass overdrive pedal for your dirt.
  5. You can try running a boost before the amp, over-driving the preamp tubes. They may get you where you want to go.

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