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  • I also have a question regarding tubes for my JCA50. Power tubes actually. I find that on the overdrive channel with the master level half way up and the overdrive preamp at 4 or above,

    the overdrive tone is way too fizzy or filled with sonic trash if you will that the tone gets lost in the mix. The fundamental note articulation is there, but underneath is all this

    unwanted sizzle, fizz, sonic noise that is bothersome to me. I have changed all of the preamp tubes and that helped a little. I am wondering if changing power amp tubes would

    help. Or is the nature of this amp, due to parts, construction, etc? Is there perhaps a mod that cleans this up? Thanks for any input. I want to like this amp, but am not digging

    the high gain the way it is currently.

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    • Quote Originally Posted by Gwimlock
      View Post

      Hey guys, I'm curious about preamp tube replacements for my JCA50H. Currently running a set of JJs in there which sound great, but I don't have much of a clean channel at stage volume. I was wondering if anyone had experimented with lower gain tubes. I know that lower gain isn't the point of the JCAs, but I'm currently running the drive channel with the Gain at 4, and am boosting it with a Swollen Pickle/Custom Comp if I need more. Would having less-gainy preamp tubes increase headroom in the normal channel while allowing me to keep the same amount of gain in the drive channel (with the gain control set higher, obviously...)?



      Thoughts? Suggestions?




      use a 12dw7 on v1. it is one half 12ax7 and one half 12au7. However I recommend that you try the clean crunch switch and the scoop mod, they do a pretty convincing fender imitation.
      Jca 50h/ 100h/ 22h Mod thread and Owners Club
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      • So for someone like myself who is not exactly proficient with a soldering iron and generally terrible at electrical work - how much would it cost a tech to install the clean/crunch switch, the SLO mods (if they can be done for the 22h), and maybe the depth knob?



        I really dig the tone of the amp as it is, but would love to try out some of these mods.
        Originally Posted by DunwichAmps


        meh. more fuzz and dist

        Comment








        • Quote Originally Posted by t-rey
          View Post

          So for someone like myself who is not exactly proficient with a soldering iron and generally terrible at electrical work - how much would it cost a tech to install the clean/crunch switch, the SLO mods (if they can be done for the 22h), and maybe the depth knob?



          I really dig the tone of the amp as it is, but would love to try out some of these mods.




          NO sure I do my own mods. I'm planning on opening my own little mod shop in the summer (about 4/5 more weeks for me)
          Jca 50h/ 100h/ 22h Mod thread and Owners Club
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          • I gotcha - if I decide to do it in the future I may send it your way. Or if I get it done locally, I will post up what the price was in case other people are curious.
            Originally Posted by DunwichAmps


            meh. more fuzz and dist

            Comment


            • Rshafer, i used to have the same problem with my jca100, then i discovered my bias was around 9.7ma. Turned it up to 42 ma and the fizz was gone.
              Gear : peavey wolfgang special, gibson les paul studio alpine white, mexican floyd rose strat,jet city 100h,jet city 4x12 cab, engl 1x12 (vin 30), engl 1x12 cab (k 85) ,weeping demon wah, bad monkey, ibanez ts9, tc corona chorus, hardwire delay, boss volume, tc polytune mini, cort acoustic, various line 6 stuff...

              "in your darkest hour you strike gold."

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              • Quote Originally Posted by koen77
                View Post

                Rshafer, i used to have the same problem with my jca100, then i discovered my bias was around 9.7ma. Turned it up to 42 ma and the fizz was gone.




                Thanks man. I'll have the bias checked next to see if that will help it out.

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                • Lte us know
                  Jca 50h/ 100h/ 22h Mod thread and Owners Club
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                  • So I will do the basic SLO mod soonish.



                    Still not sure if all parts will match.

                    Here is what I got:



                    For the pre-gains:

                    2 x Alpha 16 PCB 500k log



                    R41 + R42:

                    Xicon Carbon Film Resistor 470k / 1 Watt



                    R19:

                    Xicon Carbon Film Resistor 220k / 1 Watt



                    C28:

                    Ceramic Disc Capacitor 470 pF / 2kV

                    (might also reuse C21 for that of applicable?)



                    C21:

                    Orange Drop 0,001
                    Proud Member of the Jet Setters (Jet City Lounge)

                    * ENGL Powerball * Jet City JCA100H w/simple clean mod, depth mod * Line6 Spider Valve HD100 Mk1 *
                    * Marshall 1960AV loaded with V30s * ISP G Major *

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                    • Quote Originally Posted by kocher
                      View Post

                      So I will do the basic SLO mod soonish.



                      Still not sure if all parts will match.

                      Here is what I got:



                      For the pre-gains:

                      2 x Alpha 16 PCB 500k log



                      R41 + R42:

                      Xicon Carbon Film Resistor 470k / 1 Watt



                      R19:

                      Xicon Carbon Film Resistor 220k / 1 Watt



                      C28:

                      Ceramic Disc Capacitor 470 pF / 2kV

                      (might also reuse C21 for that of applicable?)



                      C21:

                      Orange Drop 0,001
                      Jca 50h/ 100h/ 22h Mod thread and Owners Club
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                      • Thanks, Edge!



                        As the Orange Drops are polypropylene caps they should be okay I guess.

                        Maybe I can find a proper silver mica somewhere or else I just go with the disc cap for now.

                        Is 300V enough for the silver mica or should I go for 500V?



                        Edit: Just ordered those: CDE 470pF 500V 1% Silver Mica Cap
                        Proud Member of the Jet Setters (Jet City Lounge)

                        * ENGL Powerball * Jet City JCA100H w/simple clean mod, depth mod * Line6 Spider Valve HD100 Mk1 *
                        * Marshall 1960AV loaded with V30s * ISP G Major *

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                        • Quote Originally Posted by kocher
                          View Post

                          Thanks, Edge!



                          As the Orange Drops are polypropylene caps they should be okay I guess.

                          Maybe I can find a proper silver mica somewhere or else I just go with the disc cap for now.

                          Is 300V enough for the silver mica or should I go for 500V?



                          Edit: Just ordered those: CDE 470pF 500V 1% Silver Mica Cap




                          You should be good. Let us know how it goes.
                          Jca 50h/ 100h/ 22h Mod thread and Owners Club
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                          • Hey everyone! I enjoy and apreciate everyones input here, Ive learned alot. Thanx a ton. Im new to the group and wanted to get a bit of much needed info on the Depth mod and the the SLO mod for my JCA50. Does anyone have a list of parts needed and photos of the "event". Im going to attempt it myself and need as much help as I can get. I do have some audio electronics experience and im pretty handy with a soldering iron. Ive just never attempted anything inside of an amp before... Hell, if one of you guys sell a kit, that would be the greatest! Thanx again for all you guys do and ill be waiting to hear from ya!

                            Comment


                            • Well whats your preferred distributor? and how much of a rush are you in to get the mods done. Mouser has more selection and aes should have the parts at your house by the day after tomorrow if you order today.
                              Jca 50h/ 100h/ 22h Mod thread and Owners Club
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                              • Not a big rush. I actually have 2 JCA50s because I like it so much, a backup is a must... so i got the time. Whats more important is a complete and accurate list and instructions. As far as didstributer, as long as I get the right stuff, it doesnt matter. Are there kits available?

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