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Blues Deville reissue tone control acts like bass control in reverse

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  • Blues Deville reissue tone control acts like bass control in reverse

    Hello folks, been very busy with biz & neglectful of forum. I'll have to change that.

    Anyway, I have a reissue Blues Deville that the treble control acts more like a bass control in reverse. IOW, turn it up & the bass is cut (hi's pretty much stay the same). Turn it down & you get more bass. The bass control & mid don't seem to have as much affect on the sound as they should, but act fundamentally normal.

    There are no bad components in the circuit as well there are no incorrect value controls or components. There are no bad traces or grounds missing. The tone stack is a pretty basic Fender stack as shown on schemo.

    Does anyone have personal experience with this model and remember how the treble control behaves normally?

    I have noticed that if I unload the stack by removing the connection to the drive control, or setting amp to 'no drive' and lifting R16 12K resistor, the treble control then operates normally (see attchd schemo).

    The drive pot and R-16 are the correct values as well. Fiddling with the values doesn't seem to be of any benefit either.

    I'm of a mind that this amp is operating as it was designed. Any ideas?

    I notice that in the HR Deville/Deluxe, they separated the drive control from the stack by one 12AX7 stage. Perhaps this is partially the reason. Thanx, glen
    Attached Files

  • #2
    Originally posted by Mars Amp Repair View Post
    Hello folks, been very busy with biz & neglectful of forum. I'll have to change that.

    Anyway, I have a reissue Blues Deville that the treble control acts more like a bass control in reverse. IOW, turn it up & the bass is cut (hi's pretty much stay the same). Turn it down & you get more bass. The bass control & mid don't seem to have as much affect on the sound as they should, but act fundamentally normal.

    There are no bad components in the circuit as well there are no incorrect value controls or components. There are no bad traces or grounds missing. The tone stack is a pretty basic Fender stack as shown on schemo.

    Does anyone have personal experience with this model and remember how the treble control behaves normally?

    I have noticed that if I unload the stack by removing the connection to the drive control, or setting amp to 'no drive' and lifting R16 12K resistor, the treble control then operates normally (see attchd schemo).

    The drive pot and R-16 are the correct values as well. Fiddling with the values doesn't seem to be of any benefit either.

    I'm of a mind that this amp is operating as it was designed. Any ideas?

    I notice that in the HR Deville/Deluxe, they separated the drive control from the stack by one 12AX7 stage. Perhaps this is partially the reason. Thanx, glen

    Try to replace C46 (22uF / 500V).

    Comment


    • #3
      I just put it into Duncan's tonestack calculator with a 45k load (R15+R16, R17 shorted), and what you describe seems to be normal. Compared to a 1M load it shows -10dB attenuation and a somewhat big-muff-like behaviour.

      Comment


      • #4
        Hi,
        Don't know if it will make a difference here but you have posted the old schemo, the reissue is different on some places.
        I think the schemo is on the Fender downloads site.
        John
        PS my experience has been when the trb control cap is of a small value then the range does go from dark to very toppy brite.........Think AC30 as an extrem example

        Comment


        • #5
          What you see/hear is normal *in this case*.
          The tone stack is classic Fender ... but those usually are loaded by a 1M pot and little else.
          This one is *heavily* (and this is an understatement) loaded, which chokes it to death.
          What were they thinking?
          Your ears, and Albert K's simulation match perfectly.
          Do not forget that to worsen things, it's driven by a generator with about 50K internal impedance.
          Oh well, they are Fender, they have so much good Karma accumulated from Leo's era that they can do almost *anything* with impunity.
          Juan Manuel Fahey

          Comment


          • #6
            Hi,
            Blues deville/deluxes reissue schemo
            John
            Attached Files

            Comment


            • #7
              thanx all,
              I can see where the HR models have the tonestack directly feed the next stage with nearly no load. this one as mentioned has the drive control as well as the 12K resistor for non-drive scenario to set the gain of this stage. I guess the loading changes the entire action of the stack. Don't know why Fender did this, but glad to know it's apparently normal...thanx, glen

              Comment

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