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I was asked to design a 30watter that is very, very clean and easy to DIY. My head immediately thought Fender AB763 circuit with 6L6GC's.

To keep it simple I opted for a single channel deluxe type combo driving a 12inch Weber. I do not really recommend fixed bias for first time builds, so a cathode bias topology will be used. To keep things clean, I am going to opt for ultra-linear output stage that can be switched to pentode for electric blues service. Here's a schematic of my proposal:



I rolled an output transformer with ultra linear taps and moved on to the power transformer.



Simulation of the power supply looks like this:



Rolling the power transformer has turned out a bit difficult. I am now at my third attempt; third time lucky they say :-\

    WOW I WAS JUST CHATTING TO BOTTLEDTONE A FEW DAYS BACK ABOUT A GOOD CLEAN TUBE AMP.TALK ABOUT COINCIDENCE......

    keep me posted to how it develops.. love to hear it when it's done......
      they dont come cleaner than my elk.

      twas ok when i got.

      twas freakin awesome when jp finished with it..

      love the pics K.

      keep us updated
        I think there might even be people who would be interested in this sort of design, if they are happy with their faux amp modelling.

        (I'm probably one of them ?)
          My amp has this ultralinear switching as well and I must say it cleans the sound up, to the point that I mainly play acoustic or chorused sounds through it. For fat rhythm and even for clean rhythm I rather opt for penthode mode. In any case, a recommended feature to have if you want clean tone!
            Thanks for the enthusiasm ?

            I'll keep you posted. The idea for the UL switch is for acoustic playing. Pentode mode should deliver classic deluxe/princeton sound.
              5 days later
              After three days of rolling the power transformer I tested it yesterday. No short circuit and voltages are within spec, but slightly on the high side.

              With 225VAC going in at the mains side I get

              470V DC with a current draw of 70mA
              6.7VAC on the filament tap

              I am happy with the outcome; under full load the levels should drop a 10%.

              Now for the turret board...
                Coool project. Very interested in how this turns out.
                  Here's a preview of the turret board - you have to guess the values of the components ?



                  The Negative Feedback loop stays disconnected for now, but the resistors are in place. Volume/Treble/Bass not drawn in. Brown things are resistors and Yellow things are coupling caps. Light Blue things are electrolytic caps.

                    2 months later
                    I have made a drawing of the layout on the turret board:





                      Karel wrote: I have made a drawing of the layout on the turret board:


                      Where do you buy such a long napkin with grid lines printed on it? ? ?
                        19 days later
                        @Aja: they should bring out grid printed napkins for amp builders :?

                        Here's some pics of the turret board manufacture.





                        I have decided to put the first filter caps off board, due to their size.

                          14 days later
                          So, the kit has arrived from Karel and work is about to commence. Now to clean up that workshop... yikes! what a mess, might take me weeks to clear some space... Anyway, when that is done, we'll start with wiring up the turret board. Watch this space for photos.
                            11 days later
                            Right, ready to go, just waiting for final circuit diagram and components. Any idea when I'll get these, Karel?
                              You know, if you want VERY clean, i would suggest solid state. Just saying. "Distortion" was originally a side affect of having tubes...
                                Very clean also means no transient intermodulation distortion and no higher order harmonics, so you want to steer clear of the solid state stuff imho... 8)
                                  What you say is very true, but once you have a circuit that cancels those effects, it is cleaner.
                                    Demigod wrote: What you say is very true, but once you have a circuit that cancels those effects, it is cleaner.
                                    I think what Gearhead is trying to say is that the amp is very clean for a guitar amp. In the engineering sense of 'clean' its probably rubbish. Its very easy to make an amp without audible distortion but they are very stiff on the attack and sound sterile. The whole point of a valve amp is that they're not clean, even tho we refer to 'clean' sounds as being without distortion, they prob have total harmonic distortion levels orders of magnitude higher than the average hifi amplifier. Its what makes them sound 'warm'.
                                      Oh ok sorry bit of a misunderstanding here lol. Sorry XD ?