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Cathode Follower Buffer Pedal.

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  • #16
    Hi, dear fellow nfxp.
    Part 1:
    I won't question your motives for doing this project; to each his own
    I understand that the "drool over/cool factor" is an important Human motivation, otherwise why should so many *monster* manufacturers be dropping "decorative" tubes into otherwise well made and good sounding products?
    I must confess myself also guilty of doing it, at least a few times, to avoid losing sales to fanatic, absolutely unreasonable customers who loved my sound (otherwise I would not have even bothered) but wanted to see some glass and an orange glow somewhere in the chassis.
    (by the way, the blue Led underneath usually means that the tube is *not* connected; I would use amber).
    And what did I do?
    You guessed right : a tube buffer !!!!! (between preamp and power amp)
    Why?
    Because it did *nothing* audible, I did not want to mess with the sound I already had.
    What did I use?
    Any tube I had left over .
    "any" as in "ANY" , all work.

    I wound an extra 6.3VAC filament winding.
    The "high voltage" comes straight from the power amp rails; end to end I have either 84V (100/200W amps) or 140V (300/600W amps).
    No, I didn't forget the cathode biasing resistor, it just isn't needed there.
    Yes, the supply filtering is not perfect, there is a very slight hum present , it contributes to the "tube mojo". (no, I'm not kidding, there are respected "tube amp emulator" makers who inject a little 60/120Hz hum on purpose to the same end)
    Which tube to use?:
    any 12A*7, I used many 6AV6 or radio/TV tubes I got in lot buys, you name it.
    Pentodes can be triode connected easily.
    *Octal* tubes provide VERY POWERFUL Mojo.
    Best part is that they all "work": they take 30 seconds to heat, sound fades in smoothly, if you pull them from the socket the amp becomes mute, etc.
    **Some guys heard huge differences between different brands**
    Oh Pavlov, you were a real genius !!!

    Part 2:
    a) Don't know how you reach "115V" there; quadrupled 12.6V (you said you fed your filaments with that) can at most provide around 64V, end to end.
    b) I guess your filament winding is not center-tap grounded, that would explain a lot of "buzzing".

    Part 3:
    If all that matters is Mojo, do not even connect the tube (well, only the heaters) ; wire input jack straight to output jack or through a regular SS buffer.
    After all, that's what many real famous makers do.
    Good luck.
    Juan Manuel Fahey

    Comment


    • #17
      Originally posted by J M Fahey View Post
      *Octal* tubes provide VERY POWERFUL Mojo.
      Best part is that they all "work": they take 30 seconds to heat, sound fades in smoothly, if you pull them from the socket the amp becomes mute, etc.
      **Some guys heard huge differences between different brands**
      Oh Pavlov, you were a real genius !!!

      If all that matters is Mojo, do not even connect the tube (well, only the heaters) ; wire input jack straight to output jack or through a regular SS buffer.
      After all, that's what many real famous makers do.
      Good luck.
      JM, you're so dead-on at the heart of the matter that I don't even know if I have to ROTFLOL for what you say or cry like I was peeling a ton of onions.......

      Anyway, +1, er...no....wait...+2! (after all this is what my previous post was all about)

      Cheers

      Bob
      Hoc unum scio: me nihil scire.

      Comment


      • #18
        Damn! Next they'll be telling us that the musician is the source of tone and the amp doesn't really matter.

        I'm just bitter because my Burns Orbit Three emulator plugin isn't selling.
        "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

        Comment


        • #19
          Originally posted by J M Fahey View Post
          Hi, dear fellow nfxp.
          Part 1:
          I won't question your motives for doing this project; to each his own
          I understand that the "drool over/cool factor" is an important Human motivation, otherwise why should so many *monster* manufacturers be dropping "decorative" tubes into otherwise well made and good sounding products?
          I must confess myself also guilty of doing it, at least a few times, to avoid losing sales to fanatic, absolutely unreasonable customers who loved my sound (otherwise I would not have even bothered) but wanted to see some glass and an orange glow somewhere in the chassis.
          (by the way, the blue Led underneath usually means that the tube is *not* connected; I would use amber).
          And what did I do?
          You guessed right : a tube buffer !!!!! (between preamp and power amp)
          Why?
          Because it did *nothing* audible, I did not want to mess with the sound I already had.
          What did I use?
          Any tube I had left over .
          "any" as in "ANY" , all work.

          I wound an extra 6.3VAC filament winding.
          The "high voltage" comes straight from the power amp rails; end to end I have either 84V (100/200W amps) or 140V (300/600W amps).
          No, I didn't forget the cathode biasing resistor, it just isn't needed there.
          Yes, the supply filtering is not perfect, there is a very slight hum present , it contributes to the "tube mojo". (no, I'm not kidding, there are respected "tube amp emulator" makers who inject a little 60/120Hz hum on purpose to the same end)
          Which tube to use?:
          any 12A*7, I used many 6AV6 or radio/TV tubes I got in lot buys, you name it.
          Pentodes can be triode connected easily.
          *Octal* tubes provide VERY POWERFUL Mojo.
          Best part is that they all "work": they take 30 seconds to heat, sound fades in smoothly, if you pull them from the socket the amp becomes mute, etc.
          **Some guys heard huge differences between different brands**
          Oh Pavlov, you were a real genius !!!

          Part 2:
          a) Don't know how you reach "115V" there; quadrupled 12.6V (you said you fed your filaments with that) can at most provide around 64V, end to end.
          b) I guess your filament winding is not center-tap grounded, that would explain a lot of "buzzing".

          Part 3:
          If all that matters is Mojo, do not even connect the tube (well, only the heaters) ; wire input jack straight to output jack or through a regular SS buffer.
          After all, that's what many real famous makers do.
          Good luck.
          That schematic is interesting maybe ill give it a try. My power source is so high because im using a 16v transformer which is putting out 20v. and yeah theres no center tap. Like i said THIS IS BUILT FROM LEFT OVERS!!! even the pedal enclosure is from an old project. I have learned alot from this project, even if its all what not to do. Next i would like to tackle a stand alone pre amp. to eventually hook up to my 2 vintage Bogen P.A.s that will be used as power amps and run stereo effects. Anyways that's my vision, we all gotta start somewhere. On these forums just like on the car forums everyone has an opinion and you need a reputation before your taken seriously. im sorry i dont have years of amp building expeirience so i can debate the finer intricacies of amp building. Im just here to build some stuff so id like to thank those who are helping me.

          Comment


          • #20
            Ok.
            Then I suggest you rewire your PSU with the following mods:
            1) disconnect the ground you are using now.
            Your new ground is the union of C3/C4 , which is also one of the secondary wires.
            The other wire goes both to the voltage doublers and the other end of the filaments.
            2) Now you have around +35 and -35 V.
            Build my circuit, power it from +/-35.
            It will work very well with 12AU7; somewhat less with 12AT(X)7; you can wire both halves in parallel for better results.
            3) Use much higher voltage doubler capacitors, use at least 220uF for C1/C2 ; 1000uF or more for C3/C4.
            Juan Manuel Fahey

            Comment


            • #21
              Don't forget a couple of 100Ω resistors to make that virtual voltage tap for the heaters. I like what you're doing.

              If you want a bit of both gain and buffer use a 12au7 wired like V2 of a Marshall — but a small 100K or 220K pot and lower plate/cathode resistors.

              Comment


              • #22
                Originally posted by J M Fahey View Post
                Sorry for the cold shower, but why this tube buffer?
                *Any* op amp buffer , or even a single Fet, Mosfet or even humbler bipolar will work better than this.
                Certainly won't have buzzy crackling, etc.

                See how you are with all this technical stuff about buzz and crackling and stuff. Now go look at that picture again. Anything that awesome looking has got to find a place on the pedal board whether it's any good or not.

                Not that I don't agree with you ...
                My rants, products, services and incoherent babblings on my blog.

                Comment


                • #23
                  A small suggestion...

                  If you want a "cool" looking tube pedal that actual does something useful, why not try the Valvecaster? Beavis Audio Research

                  It's a low-medium gain overdrive pedal that can be modified to a clean booster, heavier OD, or even a tube-tremolo. Huge discussion thread for it with lots of info and mods ( and yes, starved-plated is perfectly reasonable for this kind of effect).

                  Comment


                  • #24
                    If you want to replace around 7.5K/1M these values​​, you can double-click the input headroom, but you will not have much of current drive, which will be the first defeat the purpose of the buffer zone....
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