Announcement

Collapse
No announcement yet.

Adding a bit more treble to Silvertone amp

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    Originally posted by The Dude View Post
    Maybe try adding a "bright cap" across the volume controls? Input side to wiper about 100pf. Tweak to taste.
    Hello,
    I am going with the bright cap however, I don't have a cap that small on hand. Also does there need to be a cap on both volumes and the tone potentiometers?

    Comment


    • #17
      Just volume.
      Education is what you're left with after you have forgotten what you have learned.

      Comment


      • #18
        Of the vol control for the channel you want to make brighter.
        Consider experimenting with different values on each.
        If the vol control tends to be set low, then smaller bright cap values are better, eg <150pF.
        If set higher, then higher values may be preferred, eg 220, 470pF.
        Above example values are in regard of a 1M audio taper vol control fed from a regular 12AX7 CC stage.
        My band:- http://www.youtube.com/user/RedwingBand

        Comment


        • #19
          Hello,
          Thank you all, for all the the input in solving this problem. I took the first two suggestions as they would do no irreparable damage to the amp.
          I installed two .0001 capacitors across the volume controls. I then paralleled R11 and R12 with 1MEG resistors, apparently decreasing their value by half. I didn't know how to get it down to 220k, as it involves a long mathematical equation.
          The amp didn't lose all of the dark sound but, it is is crisper rather than muddy.
          So it turned out really well, it should function properly for many years to come.
          Thanks again to all involved.
          Last edited by SpareRibs; 12-05-2017, 10:21 PM.

          Comment


          • #20
            Originally posted by SpareRibs View Post
            I then paralleled R11 and R12 with 1MEG resistors, apparently decreasing their value by half. I didn't know how to get it down to 220k, as it involves a long mathematical equation.
            The mathematical equation is not that long and complicated.

            To compute the net resistance (Rt) of two resistors in parallel you take the reciprocal of the sum of the two reciprocals.
            Rt= 1/(1/R1 + 1/R2)

            To determine what value resistor (Radd) to add in parallel to an existing resistor (R1) to produce a specific net resistance (Rt) you take the reciprocal of the difference between the reciprocals of R1 and Rt.
            Radd=1/(1/Rt - 1/R1)

            Example: To determine what value resistor to add to 1M to bring the net resistance down to 220k.

            To simplify matters first divide both of the given resistances by 1000 (the resulting answer will be multiplied by 1000.)

            Radd=1/(1/220 - 1/1000) = 1/( 0.0045 - .001) = 1/(0.0035) = 285.7

            Therefore to approximate a resistance of 220k you can add a 270k or 300k resistor in parallel to the 1M resistance of the pot.

            These computations are easily done if you have a calculator (or calculator app) which computes reciprocals.

            Steve A.
            The Blue Guitar
            www.blueguitar.org
            Some recordings:
            https://soundcloud.com/sssteeve/sets...e-blue-guitar/
            .

            Comment


            • #21
              Steve, I've found the "ElectroDroid" phone app to work well for those calculations (as well as a pile of other things).

              This is from someone who learned to actually count back the difference from the amount owed to the amount paid, remember counting change Without a computer?

              Of course this goes back to when we were all surprised that the oil company sent someone out to put a THIRD digit on the price sign. Gas at over a dollar? What next.

              Comment


              • #22
                Or, if you don't want to learn all of those pesky formulas, just plug in the values:

                https://www.allaboutcircuits.com/too...ce-calculator/
                "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

                Comment


                • #23
                  Hello,
                  For another modification. Would stepping down (C6) from 25MFD to 10MFD further decrease bass a bit more ? I hate to get to extreme however in one of Gerald Weber's books he says decreasing the value of the bypass capacitor will add more highs. Looking for thoughts or opinions on that.

                  Comment


                  • #24
                    Partial cathode bypass is a shelf filter, rather than a roll off, ie a limited effect.
                    With the values suggested, only the super sub bass would be affected.
                    The value would need to be brought down a lot more, eg 0.1uF, before it did what you want.
                    See nickb's calculator Cathode Bypass Capacitor Calulator

                    To roll off some low end, reduce coupling caps eg C3 or 4, to 1/10 or less of their current values.
                    My band:- http://www.youtube.com/user/RedwingBand

                    Comment


                    • #25
                      Originally posted by pdf64 View Post
                      Partial cathode bypass is a shelf filter, rather than a roll off, ie a limited effect.
                      With the values suggested, only the super sub bass would be affected.
                      The value would need to be brought down a lot more, eg 0.1uF, before it did what you want.
                      See nickb's calculator Cathode Bypass Capacitor Calulator

                      To roll off some low end, reduce coupling caps eg C3 or 4, to 1/10 or less of their current values.
                      That may be technically true for the OP but on BF/SF initial gain stages I usually don't use anything higher than 2.2uF as I've found that 25uF has too much bass for my own tastes. The Dan Torres Triple Killer Mod ($10 back in 1995) gave you 3 choices: stock (25uF), Marshall-ish (0.68uF poly) and no cathode resister bypass cap at all. There is quite a difference between all 3.

                      But I haven't read the full thread here so just using a 2.2uF Ck cap probably won't do enough to solve the issue with the Silvertone amp.

                      Steve A.
                      The Blue Guitar
                      www.blueguitar.org
                      Some recordings:
                      https://soundcloud.com/sssteeve/sets...e-blue-guitar/
                      .

                      Comment

                      Working...
                      X