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  • Well, I tried Mesa (sovteck) EL84's in my JCA22 head......SUCKAGE! Horrible...increases the treble big time.

    So, yanked those ****************piles out and threw in a set of JJ EL84s.....MUCH BETTER! They are still a bit brighter than the stock chinese ones though.

    I also threw in a ECC81 into V3........Really nice so far....liking the crunch channel more now.

    I am goint to experiment with throwing the ecc81 into V2...but it will probably kill too much gain.

    Also I have a Sovtech 12ax7wa in V1.
    Originally Posted by chainsaw fats
    Can I drink your piss?




    Great people: d_dave_c, wbcsound.

    Comment



    • Excuse my ignorance on this - how would a new OT impact the amp? Would it change the level of gain at all or just make it sound bigger/better?

      i haven't changed the OT in the 20H (yet...i'm still considering it), but having done so in other amps, the result is usually a small increase in low end & headroom for the power section. it's rarely a dramatic difference, but it's there. it also affects the feel of the amp - especially if you run it loud enough for the power tubes to really be cooking. the interaction will be different than the stock OT - not necessarily "better", but different. for me, i'm really happy with the way my modded 20H sounds with the stock OT, but there's always the nagging "what if?"


      On an unrelated note: has anyone else noticed the 20H being extremely finicky about preamp tubes? many of the new/tested tubes i try in there are unacceptably noisy (this could be as much a result of crappy quality control on the part of the tube manufacturers as the amp). it usually takes trying a whole pile of them before i find the right combo...and even those start to get noisy before long.
      Tribute page to my pal/bandmate Danny, with free downloads of the Grand Ulena records

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      • Well.....I did some more tube changes on my JCA 22 Head...I have got it dialed in to where I want it!!!

        Here is what I am running:

        Power tubes: JJ EL84.

        V1: Sovteck 12ax7WA

        V2: Sovteck 12ax7WA

        V3: NOS 5751 (not sure the brand...says USA with a trianglular symbol next to it) it looks old as there is a patena on the pins.

        V4: JJ ECC81

        V5: Sovteck 12ax7WB

        Sounds GREAT to me. Cleaned up the crunch channel and obviously took some gain off the overdrive channel, BUT....it has taken a LOT OF THE FIZZ away. The amp still has a ****************-load of gain......that I just turn up the pre amp gain on OD to 5 1/2 and I am golden.


        SO: To clean up the crunch a bit, and give you a lot less FIZZY OD......try what I did^^^^
        Originally Posted by chainsaw fats
        Can I drink your piss?




        Great people: d_dave_c, wbcsound.

        Comment


        • Well.....I did some more tube changes on my JCA 22 Head...I have got it dialed in to where I want it!!!

          Here is what I am running:

          Power tubes: JJ EL84.

          V1: Sovteck 12ax7WA

          V2: Sovteck 12ax7WA

          V3: NOS 5751 (not sure the brand...says USA with a trianglular symbol next to it) it looks old as there is a patena on the pins.

          V4: JJ ECC81

          V5: Sovteck 12ax7WB

          Sounds GREAT to me. Cleaned up the crunch channel and obviously took some gain off the overdrive channel, BUT....it has taken a LOT OF THE FIZZ away. The amp still has a ****************-load of gain......that I just turn up the pre amp gain on OD to 5 1/2 and I am golden.


          SO: To clean up the crunch a bit, and give you a lot less FIZZY OD......try what I did^^^^


          Thanks for the tip - I actually just ordered a 22h yesterday and was going to post asking about tube recommendations. I actually have a 5751 around here somewhere that I'm not using, so that's convenient.

          My understanding is that V1b (or V2) is a preamp tube that is just for the crunch channel - has anyone dropped a lower gain tube in there to reduce gain on just the crunch channel?
          Originally Posted by DunwichAmps


          meh. more fuzz and dist

          Comment


          • Thanks for the tip - I actually just ordered a 22h yesterday and was going to post asking about tube recommendations. I actually have a 5751 around here somewhere that I'm not using, so that's convenient.

            My understanding is that V1b (or V2) is a preamp tube that is just for the crunch channel - has anyone dropped a lower gain tube in there to reduce gain on just the crunch channel?


            You can try V2 or V3.

            I should have tried that...but I buttoned the amp back up last night.
            Originally Posted by chainsaw fats
            Can I drink your piss?




            Great people: d_dave_c, wbcsound.

            Comment


            • I will probably drop the 5751 in that spot once I get a feel for the amp and will post letting you know if it makes any positive difference.
              Originally Posted by DunwichAmps


              meh. more fuzz and dist

              Comment


              • Any OT that will work for a Marshall 18 watt or any other push/pull 2xel84 output. There are many, many companies that make them...heyboer, hammond, mercury magnetics, musical power supplies, allen (heyboer), weber, GDS (heyboer), magnetic components. They very in price from about $30-$60, except for mercury magnetics, which is $80 or so, I believe.

                Upgrading the OT in these mass-produced amps like this one will give you a significant improvement in frequency range and fidelity, which will translate into a more balanced tone overall, better low end, less harsh high end, more articulate detail, better harmonics when the output section is pushed. Yes, it will change the feel of the amp as well, because it will improve the headroom a bit, and make the amp stand up better when pushed.

                I've done this to several of the mass-produced amps, and have yet to come across one that I didn't feel benefited enormously from the change. It will, however, tend to expose sloppy playing far more than the stock iron in these types of amps, specifically because it does so much to improve note separation, detail, and clarity.

                I went with the Allen TO22 for this amp, and it made a vast improvement. It WILL change the amp, obviously, because you're swapping out the very heart and soul of the amp. I personally can't imagine anyone not being impressed with the change, but I suppose it's possible. Tone is subjective and all. The amp still has plenty of gain, but now I can hear every note ringing out clearly and bell-like, instead of having this thick, smeary wall of mud.

                As for the amp being finicky with preamp tubes, it's a fairly high gain amp, so yes, it's going to be a bit finicky about V1, for sure. That's a very important tube in any amp, but markedly so in amps with considerably gain at the front end, like this one.

                You're also experiencing the sad state of current production preamp tubes. There are some real decent output tubes being made today, but no decent 12ax7s. All of them are drastically inconsistently manufactured, so much so that it's actually rare to just blindly purchase a good one.

                The best you can do is read reviews of various tubes to get some general insight (don't take anyone person's word for any of this, but read from many sources, to gather a general consensus), buy from a reputable dealer who tests tubes and stands behind them, and try more than one brand. All other things being equal, as in the tubes you try are all of similar conductance/gain, it still boils down to personal taste.

                I've personally found the Tungsols to be pretty musical. I have had one go microphonic, so they're not any more immune to that than any other current tube, but in terms of tone, from modern tubes, I prefer them over Sovtek, EH, the latest Chinese tube, and JJ. I've read and heard from others that the Sovtek LPS is a very decent sounding tube, but I've also read and heard that it's so terribly prone to microphonics that it's very difficult to find a good one, and one that will last.

                If you do have a noisy tube in this amp, try it in another amp, with lower gain. You might find it useable in a different amp.

                Comment


                • Oh, I want to add a note, in case anybody has thoughts of tolex changes on this amp. I recently recovered mine in smooth blonde, and I have to say that the stock tolex and glue is EXTREMELY difficult to remove. Not impossible, but VERY difficult. I probably spent 4 hours of hard labor stripping mine and cleaning up the cabinet. It requires an astonishing amount of effort. Just a bit of forewarning, to anyone who may be considering it. It can be done, but it's definitely not for anyone not up to a considerable challenge!

                  Comment


                  • I will probably drop the 5751 in that spot once I get a feel for the amp and will post letting you know if it makes any positive difference.


                    Thanks. It would be interesting to see what it does in V2.

                    I just tried the amp with my strat....single coils really kill the volume on the crunch channel (I have been using my Jackson with SD Humbuckers almost exclusively).
                    Originally Posted by chainsaw fats
                    Can I drink your piss?




                    Great people: d_dave_c, wbcsound.

                    Comment


                    • I just tried the amp with my strat....single coils really kill the volume on the crunch channel (I have been using my Jackson with SD Humbuckers almost exclusively).

                      How's the pup height on the strat?

                      Comment


                      • How's the pup height on the strat?


                        Good call....I looked at them and sure enough...plenty of room to raise the pick-ups and that is what I did...helps a lot. Thanks!
                        Originally Posted by chainsaw fats
                        Can I drink your piss?




                        Great people: d_dave_c, wbcsound.

                        Comment


                        • Excellent! Glad it worked.

                          Comment


                          • Hey guys I just received my JCA20H and absolutely love it!
                            I noticed that JCA replaced the toggle switches and the blue jewel power light with two flip switches.
                            I have a feeling this will be more reliable than the jewel. It's the same style they use on the JCA22H
                            Anyone else seen this on the JCA20H yet?

                            Comment


                            • Hey guys I just received my JCA20H and absolutely love it!
                              I noticed that JCA replaced the toggle switches and the blue jewel power light with two flip switches.
                              I have a feeling this will be more reliable than the jewel. It's the same style they use on the JCA22H
                              Anyone else seen this on the JCA20H yet?



                              They switched to these new rocker switches as soon as they discovered the issue with old lights. MUCH more reliable. Of course, mine is the old version...
                              Originally Posted by buddhapaugh


                              Rocking the spandex AND the depends!

                              Comment


                              • They switched to these new rocker switches as soon as they discovered the issue with old lights. MUCH more reliable. Of course, mine is the old version...

                                My jewel was doa so the rockers are probably better. oh and guys theres a 50h/100h/ 22h thread.
                                Jca 50h/ 100h/ 22h Mod thread and Owners Club
                                Jca20H Mod thread and owners club
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