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  • #61
    Doh, should add - I've got a 500R shared cathode resistor for both power tubes, so it'd be 1K per. Right now it's got RI TS 5881s in it, which promptly cooked when I put them in my Prosonic with a shared 220R. But I guess I'll suck it up & do the work...
    Any issues with the grid stops being 10K & screen droppers @ 1K with all types? That is venturing into territory I won't pretend to grasp!

    Justin
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

    Comment


    • #62
      The 10k stoppers and 1k screen resistors are fine. In fact I had a project once with 10k stoppers, 1k screen grid resistors and 470Vp that ate three pairs of el34's. Two were new, but I suspect defective and the other was old/used though. I was out of el34's so I dropped in some 6L6's I had and was able to finish the project. Complete with extreme, sustained heavily clipped torture testing. The final tubes for that amp ended up being Ruby branded Suguang el34b's that sounded terrific (if a little too microphonic).

      I've used 500(+?)R resistance for a pair of 6L6's at 420V. That amp went through many changes and one version had one of the better cranked up tones I've ever achieved. So clearly odd distortion artifacts like crossover distortion weren't a problem.

      DO plug in the other tubes anyway for your own satisfaction. If 500R presents an acceptable bias for the JJ6V6's it should be plug and play for the different tube types. If your sockets are wired correctly and your heater winding is up to it you might even be ok with el34's or other Euro tubes.?.
      "Take two placebos, works twice as well." Enzo

      "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

      "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

      Comment


      • #63
        Okay, measurements:

        JJ6V6Ses: running about 12.25W per tube, or about 87%. No problem there...
        TS 5881RI: running about 13.62W per tube, or about 60%. No problem there, assuming they're true 23W tubes as the originals were.
        JJ6L6GCs: running about 13.2W per tube, or about 44%. Cold for sure, but I doubt we'd need any more power, given all the griping about "you're too loud!" we get as guitar players.

        I think there's enough wiggle room with the first two to not worry too much, though I guess I'd stick with the 5881s most of the time. The other nice thing about that 500R cathode resistor? It makes the math really easy!

        Granted, all of these are not "Listened To and Took Detailed Notes" or anything, just quick plug-&-chug.

        Now, as an aside:
        I've got a set of GT-branded "GTE34LS" (aka: 6CA7) [That's exactly what's printed on them] that are rebranded JJs, which I'm thinking are really JJ E34Ls, which I believe are supposed to bias using something more like 6L6 voltages, instead of standard EL34 voltages? I tried them for about 30 seconds, but given the funny noises that came out of my speaker I wasn't inclined to leave them in very long. Not even long enough to check the heater voltages, which I'm sure would be okay - this thing has a really beefy Schumacher tranny set. I don't have any other EL34s laying around, and plenty of "American" style tubes, so I'll blow through those first before buying more variety. Next few amps may be 6W6, 6AQ5, 6BK5, 7591, etc - I picked up a slew of oddballs over the years, super cheap.

        Justin
        Last edited by Justin Thomas; 05-12-2017, 08:10 PM.
        "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
        "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
        "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

        Comment


        • #64
          Another update:

          After a few more months and continued readings from others with the same problems, I dug up some old Rivera schema, the ones where there's a cap from cathode to (I forget which). Anyway, I tacked a 500oF on the EF86, and plugged it into my Bassman 2x15" and it sounded amazeballs.

          When I got home I plugged it back into my cheapie Celestions Rocket 12, and it's better, but still a bit harsh in the high end. So I either need to seriously break in that speaker (hasn't seen more than 10 hours of low-volume playing yet) or just get another old Fender cab... I don't know why those old CTS speakers get such a bad rap!

          There are a few bad connections in the preamp that'll need chopsticking, but on the whole, I'm making good (if slow) progress, and this one is becoming something more like what I would personally play out. I'll have to put up pictures of the shell, too... I unwittingly matched the colors of an Irish sunset without being aware of it...

          Justin
          "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
          "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
          "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

          Comment


          • #65
            Still tinkering with this thing, usually after being inspired by other threads I see here, and trying out the ideas. Latest is messing with the 220k (I'm guessing) grid leaks on the 6V6s. Also, trying to track down some mechanical noises. What did I learn? Seems that tube sockets are not something to cheap out on...

            Justin
            "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
            "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
            "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

            Comment


            • #66
              After much enjoyment and frustration, I have elected to go a more "conventional" route - partly due to EF86 issues. I reworked it over today, with a regular 12AX7 preamp. I left the Dr. Z tone controls, but am going to swap them out for something a little more "lossy." This thing has super gain, too much. But I think at the end of the day (or month, or whenever) I'll have something more "me." I learned a lot here, and thanks again to all. I'll check in periodically here with updates.

              Justin
              "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
              "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
              "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

              Comment


              • #67
                And, my first iteration (BF Deluxe Normal preamp) results in nothing but a loud BUZZZZZZZZ when the Volume control is advanced, with no trace of a guitar signal... So, once again, we learn, don't work on your amp when you're tired! Wiring check tomorrow...

                Justin
                "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
                "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
                "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

                Comment


                • #68
                  Second iteration squeals! Garsh, I love point-to-point! But the buzz is gone. So, now to futz with layout. Knobs work properly, at least.

                  Edit: found broken ground in my Tele. Standby...
                  Edit Edit: some hum to track down, but LOTS of loud. Sounds like a 2x6L6 Fender should. Probably will have to dump some gain; time to look at some high-gain amps schematics for voltage dividers...

                  Justin
                  Last edited by Justin Thomas; 01-09-2018, 03:07 AM.
                  "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
                  "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
                  "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

                  Comment


                  • #69
                    I haven't been following this thread from the beginning, just looked at it today. I was going to ask what you've been using for the preamp pentode and how reliable it's been. Since you're converting over to a twin triode preamp I thought I'd ask -- why did you end up bagging the pentode?
                    "Stand back, I'm holding a calculator." - chinrest

                    "I happen to have an original 1955 Stratocaster! The neck and body have been replaced with top quality Warmoth parts, I upgraded the hardware and put in custom, hand wound pickups. It's fabulous. There's nothing like that vintage tone or owning an original." - Chuck H

                    Comment


                    • #70
                      Originally posted by Justin Thomas View Post
                      Sounds like a 2x6L6 Fender should. Probably will have to dump some gain; time to look at some high-gain amps schematics for voltage dividers...
                      got and updated schem?
                      "Stand back, I'm holding a calculator." - chinrest

                      "I happen to have an original 1955 Stratocaster! The neck and body have been replaced with top quality Warmoth parts, I upgraded the hardware and put in custom, hand wound pickups. It's fabulous. There's nothing like that vintage tone or owning an original." - Chuck H

                      Comment


                      • #71
                        Not until it works and I like it!

                        Justin
                        "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
                        "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
                        "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

                        Comment


                        • #72
                          Originally posted by bob p View Post
                          I haven't been following this thread from the beginning, just looked at it today. I was going to ask what you've been using for the preamp pentode and how reliable it's been. Since you're converting over to a twin triode preamp I thought I'd ask -- why did you end up bagging the pentode?
                          I was using an old Mullard EF86, switched off with a JJ or a Seimens. They all made various noises to some degree - rattles, etc. I put in a shock-mounted tube socket, dampers on the tube, all the usual stuff. I just got tired of fighting it.
                          The JJ was good, but after some hours, plop...

                          So between the frustration of that and the fact that it was originally built for someone else, I never liked it enough to say, "I'll play this one today." I'm an unashamed Fender guy, so I decided to rebuild it into something <I> want to play. And, even though there are some setbacks, I think I like it better already.

                          Justin
                          "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
                          "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
                          "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

                          Comment


                          • #73
                            Hey All,

                            I know it's been forever, but I think I finally wrapped this dopey amp up!

                            It's now essentially a SF Fender Normal channel & PI/output, with a tweak to the Treble control to give finer control, and an added Matchless/Vox-style Cut control. I finally have a useable tone control system for it, not too tubby & can get as bright as you want but still have pretty fine treble control. I've changed a few resistor values on the power tubes, just for a better safety margin. I'll see if I can draw up a final schemo &take some voltage checks & stick em here later on.

                            Thanks for all the ideas, help, & I've learned a decent bit through all this.

                            Justin & Jusrin
                            "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
                            "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
                            "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

                            Comment


                            • #74
                              Originally posted by Justin Thomas View Post
                              Hey All,

                              I know it's been forever, but I think I finally wrapped this dopey amp up!

                              It's now essentially a SF Fender Normal channel & PI/output, with a tweak to the Treble control to give finer control, and an added Matchless/Vox-style Cut control. I finally have a useable tone control system for it, not too tubby & can get as bright as you want but still have pretty fine treble control. I've changed a few resistor values on the power tubes, just for a better safety margin. I'll see if I can draw up a final schemo &take some voltage checks & stick em here later on.

                              Thanks for all the ideas, help, & I've learned a decent bit through all this.

                              Justin & Jusrin
                              It's not done till we have a clip of you playing it.

                              nosaj
                              Binkie McFartnuggets‏:If we really wanted to know the meaning of life we would have fed Stephen Hawking shrooms a long time ago.

                              Comment


                              • #75
                                Not happenin'! Mostly cuz I don't know if I can put up a phone recording... And unless y'all are gluttons for punishment.

                                Jusrin
                                "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
                                "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
                                "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

                                Comment

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