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Fender Bassman Reissue LTD Master Volume Mod

Discussion in 'Amp Tech Center' started by nathanh, Oct 13, 2016.

  1. robrob

    robrob Poster Extraordinaire Ad Free Member

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    The super simple Type-3 master volume works great for most amps. The much more complex and difficult to install Type-2 can be better (if the dual pot is evenly matched) but the Type-3 is more than good enough for most of us.
     
  2. nathanh

    nathanh Tele-Meister

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    Awesome!!! I'm an audio engineer (pro tools ) and spend lots of time correcting phase in multi source recordings like drum kits or dual mic'd guitar cabs so once Rob explained it (or I read where he had to someone else) it made total sense and blew my mind. Some hate on the tone but I love it.

    Type 4 isn't too bad either! I didn't even have to remove the board connected to the pots to do it. I've been using the Type 4 as my master and keeping the Type 3 up to 75% (or less if home) to knock out hiss and better dial in the sweet spot. Studio amp heaven.

    I also wired the bright and normal channels together so at any time I could just bright or normal or both just by turning the knobs. The only thing this omits is if you use an ABY switch and float between the two channels but at the volume I use it they're not that different. I move em both up evenly always. Good gain!

    IMG_0627.JPG
     
  3. nathanh

    nathanh Tele-Meister

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    Reviving this old thread to learn something new. I'd like to know both if this would work and then opinions!

    When using the PPIMV turned down just a little bit I remember it knocked off more noise than volume. I mean the amp is loud as all hell anyways so turn it down 10 percent means nothing I'd say. Correct me if Im wrong.

    So let's say I want to install a resistor instead of a pot that would lower the volume by 10 percent. Just enough to cancel out some noise. Would I just stick an 820k ohm resistor across the power tube grid leaks?
     
    Last edited: Jan 7, 2019
  4. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Keep in mind volume isn't linear but yes, an 820k resistor would do the same as a 1M pot rolled down to 820k.
     
  5. nathanh

    nathanh Tele-Meister

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    Do amps every have this or is it sort of a non issue? I tried 820k, not very much happened. Might experiment with lower values for fun.
     
  6. robrob

    robrob Poster Extraordinaire Ad Free Member

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    I've never seen a power tube grid to grid resistor to work as a fixed "master volume". Typically if you need to adjust the gain of the signal at the power tube grids you use a voltage divider in the preamp as an attenuator.

    You can temporarily clip in a 1MA pot and roll down the volume to what you like, then read the resistance of the pot, then replace the pot with a resistor of that value.
     
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  7. Lynxtrap

    Lynxtrap Tele-Holic

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    What kind of noise is this? Is hiss, hum, crackling, buzz...
    IMO you seem to be about to treat symptoms without knowing what the illness is.
     
  8. nathanh

    nathanh Tele-Meister

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    Purely speculative thoughts here. The amp has since been rebuilt and is great. Nominal amp hiss. I just remembered before how helpful the mod was when just turned down a hair.
     
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