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  • 30 watt class A

    I picked up a partially assembled 30 watt (4 EL84) class a amp loosely based on the tube rectified circuit of a DC30. The amp has hammond transformers (which I guess are okay - I'm sure there are better). I had to finish up soldering some of the components and some of the tubes. I'm not sure exactly what I was doing - I just followed the directions I was given. When I first powered the amp up I was pretty much scared to death but it all worked just fine. The amp is very chimey with single coils but I like it best with HB's - the controls are volume, treb, bass and presence - the EQ controls are very interactive - crank them both up and the amp really crunches, the presence really doesn't seem to do all that much. There's a tube effects loop but I haven't tried it out, there's no mix control so I'm not sure how it will turn out. I put together a cabinet with spare Pine and plywood - the tolex was left over from a cabinet recover I did a few years back, I didn't have enough to go all the way around so I had to do some patching. I used a reverend alltone 12" speaker I've had sitting around for a couple of years - I'm very surprised at how it sounds. I replaced the rectifier tube and the EF86 tubes with some Mullards I had from another project. All told I've got about $200 into the amp. I still have some finishing to do - which I'll probably never get to!

  • #2
    Re: 30 watt class A

    Schwweeeetttt!

    Nothing wrong with Hammond Trannies. You built a 30 watt Lightning with an EF86 V1. Nice!

    If you only have 200 into that, you won the game this week! beautiful sound in these things.


    www.CelticAmplifiers.com

    "You can't save everybody, everybody don't wanna be saved."

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    • #3
      Re: 30 watt class A

      2 preamp tubes? One ef86 and a phase inverter?


      www.CelticAmplifiers.com

      "You can't save everybody, everybody don't wanna be saved."

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      • #4
        Re: 30 watt class A

        Cool score!...actually hammond trannies are the best current production ones available... just in my opinion of course!

        Jeff Seal
        ..lots and lots of toys!

        "...swords and tequila, carry me through the fight!"

        "I am Phil"....
        www.houstonamprepair.com

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        • #5
          Re: 30 watt class A

          Oh, I see the 3rd one. That's better.


          www.CelticAmplifiers.com

          "You can't save everybody, everybody don't wanna be saved."

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          • #6
            Re: 30 watt class A

            Scott, thanks for the extra info!!!

            Yes, it has a 12AX7 phase inverter! Thanks for telling me what it is! When I bought it I was only interested in the 1x12 two rock cabinet the guy was selling. He had the amp on his workbench and I asked him if he built amps - he said he had bought it partially built and didn't have time to finish it - so I picked it up with the cabinet for an extra hundred bucks. It had a name "Utopia" on the chassis, I looked on the web but found no information. I just had a board layout and schematic to finish the amp up with. I was pretty much stunned when I plugged it in and it worked, I actually put the amp on the driveway and flipped the power and standby switches on with a broom handle!!! It's very quiet and has that "vox" vibe which is pretty cool, sounds awesome with my AC booster in front of it. Now I've got the bug to try one from the beggining!
            Last edited by RiffRaff; 09-10-2005, 10:44 PM.

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            • #7
              Re: 30 watt class A

              Originally posted by RiffRaff
              Scott, thanks for the extra info!!!

              Yes, it has a 12AX7 phase inverter! Thanks for telling me what it is! When I bought it I was only interested in the 1x12 two rock cabinet the guy was selling. He had the amp on his workbench and I asked him if he built amps - he said he had bought it partially built and didn't have time to finish it - so I picked it up with the cabinet for an extra hundred bucks. It had a name "Utopia" on the chassis, I looked on the web but found no information. I just had a board layout and schematic to finish the amp up with. I was pretty much stunned when I plugged it in and it worked, I actually put the amp on the driveway and flipped the power and standby switches on with a broom handle!!! It's very quiet and has that "vox" vibe which is pretty cool, sounds awesome with my AC booster in front of it. Now I've got the bug to try one from the beggining!

              what you did was probably harder in a lot of ways, taking over someone elses work and fixing it.

              now you know what Jeff probably has to do on a weekly basis! fix buggered up modified amps and such!

              to be technical, when you stick that ef86 in there, you lose a bit of the Lightning smoothness, but you crank that gain up a bit, eh?


              www.CelticAmplifiers.com

              "You can't save everybody, everybody don't wanna be saved."

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              • #8
                Re: 30 watt class A

                that's quite a nice sleeper project, especially for the $$$ you've got into it

                your comment about the presence control is interesting - I thought those were supposed to be quite effective - in the DC30s at least.

                I've tried the Alltone, and it was pretty good in my DRRI, but I settled on a G12H30 (actually, an Avatar Hellatone 30), and I have a feeling a Celestion might sound better in that amp, but if you're happy with the tone, why bother?

                just crank it and enjoy!
                "music heals"
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                • #9
                  Re: 30 watt class A

                  a 30w lightning should have some decent volume

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                  • #10
                    Re: 30 watt class A

                    It's loud no doubt - and it crunches nicely when up about half way (far louder than I'll ever be allowed to turn up in the clubs I play). Takes pedals very well. I wasn't at all familiar with EF86 wiring so I didn't know what to expect, I changed the sovtek 12AX7 with a telefunken I had and now there's definitely more change in the presence when it's adjusted. Not sure why?? I think I might pick up a Hellatone from Avatar - I have one in the 18 watt marshall clone 1x12 combo I use and it sounds excellent. Overall it was a fun project!

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                    • #11
                      Re: 30 watt class A

                      Great - We need to hear more about projects like this on the AMP section of this forum...

                      PS: Soldering workmanship looks great!
                      Support Code 211 - Stop the bad boys, you know COPS!
                      When we do right nobody remembers when we do wrong nobody forgets!
                      Red Devils - 1% all the way!
                      Screw anyone who post negative crap on my post!
                      Finding out that there really is a lot of traffic on the Highway to Hell, but no waiting line on the Stairway to Heaven.

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                      • #12
                        Re: 30 watt class A

                        I missed the part about the presence control, now you're getting further away from a Lightning. Lightning has vol, bass, treb and master. If you want to rewire that presence as a master, let me know. we can compare schematics and I think you'd like the results.


                        www.CelticAmplifiers.com

                        "You can't save everybody, everybody don't wanna be saved."

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                        • #13
                          Re: 30 watt class A

                          Thats a pretty nice looking amp for something that you pieced together. Great bargain too.

                          Artie

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                          • #14
                            Re: 30 watt class A

                            I hate that I'm becoming the resident crank about this, but that's not a class A amp; it's cathode biased. Class A describes a particular range of biasing wherein both tubes are active throughout the entire wave form. There's no way 4 EL84's in class A will put out 30 watts.

                            Cathode biasing is a method of biasing (as opposed to fixed biasing). Either method could be used to bias tubes in A, A/B, or any other class.

                            Refer to the masterwork on this subject, "Is the Vox AC-30 Really Class A?" on the Advanced Tech page on Randall Aiken's web page .

                            Regardless, cathode biased 4xEL84 amp rock. Looks like you gaot agreat amp and a great deal. Welcome to the DIY club.
                            Tra-la-laa, lala-la-laa!
                            Rich Stevens


                            "I am using you; am I amusing you?" - Martha Johnson, What People Do For Fun

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                            • #15
                              Re: 30 watt class A

                              Originally posted by RiffRaff
                              the presence really doesn't seem to do all that much.
                              That looks like a top cut control a la Matchless and Vox--a pot and cap wired across the PI plate outputs. Turn the volume up to 8 and it should be a more effective top end control than the treble, which will be more of a top end gain control at that point. There's also no 47pF oscillation/ smoothness cap across the PI plates, which means it may oscillate and/or sound harsh as you overdrive the PI, which is another great reason to have the cut control.

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