Bassman 10 Normal Channel Tone Stack

Discussion in 'Amp Tech Center' started by separateness, Feb 27, 2020.

  1. separateness

    separateness TDPRI Member

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    Can any one tell me what exactly is going on with this tone stack? It looks like a two-tiered shelf for the Treble (?). And then... something else altogether for the Bass? It almost looks like a James stack turned inside out. Any elucidation would be appreciated.[​IMG]
     
  2. LetItGrowTone

    LetItGrowTone Tele-Meister

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    Unless someone builds one in a circuit simulator I don't think we will get any more than "similar to a James".

    There are many different circuit simulators, and my contribution to the thread is to point you to the one I've used a few times, LTSpice XVII. That's all I have for you.

    You could do that and then compare to the James simulation in the Duncan Tone Stack Calculator or at http://www.guitarscience.net/tsc/james.htm (tone stack calculator online). Actually, that could be your first approximation to how the one in the Bassman 10 behaves. Go to that James simulation, move the treble and bass sliders, and see that there's no inherent mid cut.
     
  3. separateness

    separateness TDPRI Member

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    I've actually spend a lot of time with the online TSC (which is, by the way, awesome) and am pretty familiar with the way the James reacts to various values and settings. I've been looking into tone stacks pretty heavily of late because I have been building a bass amp and have used the opportunity to do some experimenting. The issue now is that the tone stack I have in there is the Vox configuration found on the TSC but with some capacitor values changed for a broader treble and bass controls. Essentially the treble has a knee at 1k and the bass controls everything from 250 down, no rolloff.

    It actually sounds really, really good but the amp I built is very simple with two gain stages before the phase inverter and I would like to get a little bit of grind out of the second stage and would like to minimize the tone stack insertion losses. As it is I can get it just barely to break up, and really I should probably be happy with what I got but I can't stop messing with it.

    Anyway this Bassman 10 configuration looks at first blush to be relatively low loss, but maybe I am wrong here. Perhaps I should be looking elsewhere.
     
  4. LetItGrowTone

    LetItGrowTone Tele-Meister

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    I'm also playing bass, and my bass amp project last year was also simple, with two gain stages before the phase inverter. But I'm not the guy to advise you, as I also couldn't decide what I wanted, and I'm not even using it at this time.

    Be careful with that, sincerely.
     
  5. galaxiex

    galaxiex Tele-Afflicted

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    Looks like a bridged Tee notch filter...
     
  6. separateness

    separateness TDPRI Member

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    Ah, I think you are right. I think I may have been barking up the wrong tree by investigating this circuit anyway, as with the two bands in parallel, it surely has a good bit of insertion loss. I am thinking now of putting a pot in series with the cathode bypass cap of the second gain stage (which is as of yet unbypassed) as a sort of high/sparkle shelf filter ~800Hz. Not sure where to go with the bass control though. Ah well. I hate that I love the sound of this amp so much but it just can't give me the dirt I want available in its current configuration.

    Be careful because of the manic addiction to experimentation or because of the potential lethality of messing around in a tube amp? Either way is a dangerous course.
     
  7. LetItGrowTone

    LetItGrowTone Tele-Meister

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    Addiction.
    When I was younger I was immersed to a ridiculous degree in tube amps for 6-string guitar.
    Now that I'm playing bass I was determined to actually study music this time, but so far have been tangled up in equipment questions again. Need to try to get out of it, but have amp and bass parts spread out at the moment. Oh well, off topic.
     
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