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  • This is for all the new amp modders out there!

    What is the Depth Mod and what does it sound like:

     

    JCA22H

    Guitars: Fender Stratocaster (Deluxe Lone Star), Ibanez S420, PRS SE245, PRS Custom 24. Various Duncan & Dimarzio Pickups.
    Amps: Marshall TSL100 (Various Tubes, no mods)
    Cabinets: Egnater Tourmaster 4x12 w/ Celestion Vintage 30s
    Effects: Digitech RP1000, TC Electronic Nova Drive
    Favorite Guitar Player on YouTube: Satsuma3042

    Comment


    • For all you new amp modders!

      How to verify voltage before working on your JCA22: 

      (1st 5:25 cover voltage verification, rest of video shares what I have learned about voltage and the JCA22).

      Guitars: Fender Stratocaster (Deluxe Lone Star), Ibanez S420, PRS SE245, PRS Custom 24. Various Duncan & Dimarzio Pickups.
      Amps: Marshall TSL100 (Various Tubes, no mods)
      Cabinets: Egnater Tourmaster 4x12 w/ Celestion Vintage 30s
      Effects: Digitech RP1000, TC Electronic Nova Drive
      Favorite Guitar Player on YouTube: Satsuma3042

      Comment


      • The "predator" mod on my jca22 is definitely a step on the right direction. My complaints with the stock tone were a lack of low end definition and harsh high end sizzle fizz. Good but not great. I'm not looking for a metal tone (I love mids. But I like palm muting to have some balls not be all flabby and round.

        The depth mod was a given. I put a resonance control on all my amps anyway.

        After the predator mod, the overall tone seems more focused. It's not metal I don't think. Just better. The lows are a bit more solid and the highs on the normal crunch channel are smoothed out. I did notice after the mod that the OD channel had some piercing highs going on. I lifted a leg of c5 (cap just before Od gain pot). And that did it. Normal and OD channels are very similar voicing wise. Like channel 2 picks up where channel 1 ends. If that makes sense.
        Preamp tubes are ruby high gain V1 and V2, tungsol RI V3, old Marshall preamp tube V4, mullard RI V5
        Stock power tubes ( JJs ordered)
        The stock power tubes are horribly mismatched!
        Plate voltage was 355
        Tried setting bias to 22ma
        Ended up 22ma on 1 and 14ma on 2. So with a proper bias it will be great.

        Comment


        • k
          käsebrot commented
          Editing a comment

          @ Motocooney:

           

          Could you please tell me, what exactly you've done to get the Predator Mod on the 22H?

          I also have a 22H, but have no idea, how to transfer the numbers and values from that mod for the 50H to the 22H schematic as they are both different.

          That would help a lot!

           


      • Also, for the depth mod posted^^^^^^above......
        A 250k log pot is much more effective. And for even more low end pronunciation, you can try a .0022uf cap.

        Oh, Edge, What are the bright caps on the 22 and 100?

        Comment


        • Borderline11
          Borderline11 commented
          Editing a comment

          Great suggestions! I will try the 250k pot for the depth mod. The next mod for me will be the SLO with the clean/crunch switch. I want to spend some time getting used to the current depth mod, then dive into the SLO. 

          I appreciate the description of how the preditor mod sounded! That helps us know what to expect.


      • So....I have a jca100h on the way
        So now my plan is to use my 22 as the guinea pig. If something sounds good then I'll apply the same mod to the 100. I wanted a 50 but got a sweet deal so I'll be running it with 2 tubes pulled. Old version no half power switch.
        I've decided that I still need to cut some highs somehow. Any ideas?
        Running vintage 30s. Which are tend to be kinda bright, my two main guitars are 79 strat w/hot rails and a newer Tele w/hot rails.
        The Ruby hg in v1&v2 helped darken it a bit but still seems bright. treble and presence are both at 3-4ish. Any lower and I'm losing tone.

        Comment


        • Well, I still have to read through all the posts in here, but you guys have definitely inspired me to buy one of these amps or build another SLO clone and relive some of my mods from other amps. I'm also in the process of building a JCA20H clone on a turret board, so I can mod/share some of what I've done on other amp projects.

          Les Paul CustomZhangbuckersHomebrew ampsGreenbacksBlackbacksAssorted Pedals

          Comment


          • Comment


            • Hi guys,


              Been a reader of this fine forum for quite some time.

              I just wanted to say thanks to the regular contributors on here, like grimespace and edge, im sure there are quite a few others that have helped me.

              After many years of playing small ss practice combos i finally acquired a JCA50H late last year. I built a angled front 2x12 homemade cab for it to sit on.

              When I got the amp I knew there was going to need to be some mods done. Because the sound was definitely not what I thought it was gonna be. It was pretty weak and sterile until you turned it up to about 5.

              Swapped every tube out of the thing, put a JJ 5751 in v1 to lower the gain, and JJ's in the rest. Pulled the stock power tubes, put in Sovtek 6l6WXT+'s and set the bias, it was a little cold at 20ma

              Also did the depth mod...holy crap. That knob should be on there from the factory.

              Like several others I did not care for the blue on the front so I used my leftover grillcloth from the cab build and some piping and redid the head. Thinking about getting the alternate JCA logo to put on the front, the 333 ain't goin back on there.

              Thought I'd post some pics, I'm very happy with the BA rock machine that I have now.

              Thanks again for all the help!

               

              Comment


              • LProoster
                LProoster commented
                Editing a comment

                new to this still, think i got the pics right this time

                1

                2

                3

                Attached Files

            • Sure no prob.....

              Predator Mod for JCA22h

              C2-.047uf
              C7-220pf
              C5-.0022uf
              C6-1n
              C8-3.3uf
              R5-470k
              R10-680k
              R9-500k
              R18-220k

              I lifted a leg of C5 afterwards as I found that the OD channel was brighter than the normal channel

              Preamp tubes are ruby high gain V1&V2, tungsol reissue V3, old Marshall 12ax7 C4, Millard reissue V5
              JJ el84 power tubes biased to 21ma ish.

              Comment


              • k
                käsebrot commented
                Editing a comment

                Hi there,

                 

                thank you very much!


                For what I know, the C2 cap is between the 1. and 2. gainstage. Normally it's 22nF - and that is really high, 47nF seems a lot too high, will produce mud in base. You will boost very low frequencies, which are out of the speakers range - and also very high frequencies, which will lead to more fizz. I would rather go with 4,7 to 10nF here.


                C7 at 220pF is a good idea, I already have done this. The bigger JCAs have a stock 270pF/1M (C7/R10 at 22H) combination. The change of C10 to 680k and/or the C7 at 470pF (as stock at 22H) would be the "crunch mod". C7 only affects the crunch channel as far as I know - but the crunch and overdrive channel responses a little bit to each other. You will hear it when leaving the gain in overdrive channel at a certain postion and turning up and down crunch gain - while playing in the overdrive channel.

                 

                C5 should be a mid/treble filter and C6 is the bright cap for overdrive gain. They both only affect the overdrive channel. I have already tried out several values for both, but think, the stock 1nF (C5) and 470pF (C6) fits best. You can also try 470pF at C5 - that would be more Marshall style.


                I can't say anything, how the changes of C8, R5, R9 and R18, which you have mentioned, would work. Haven't tried this yet.

                 

                But I could recommend to try a 39k slope resistor (R26) instead of the stock 47k. That helps the amp to get a little bit brighter (like Orange and Diezel - Marshall would be 33k) and get a bit more bite.

                You also could change the treble cap (C14) to a higher value (stock is 470p), f.e. 500 or 560 to get the upper mids more aggressive.

                If the amp sounds too loose, a change of the NFB resistor may help. Stock is 47k at 8 Ohms, try 51k or 56k and you get a more aggressiv and tighter rhythm sound. But therefore, the leads wouldn't have that soldano sweetness.

                If you have too much fizz overall, try to change the fizz cap (C20). Stock is 270p. Higher values give you less fizz. I actually use 220p, but I also lowered the C2.

                 

                I am not an amp tech - but have talked about this amp a lot with one. So I know a few things. Maybe some of these, I have posted, will help.

                 

                Best regards!


            • Comment


              • The values I listed are the same as edge's predator mod.
                The 47nf in c2 does seem high. I used a .0047uf (4.7nf) there.

                Also, the change in the nfb resistor you mentioned is kind of covered by the depth mod.

                Comment


                • k
                  käsebrot commented
                  Editing a comment

                  Oh ok!


                  You wrote "C2-.047uf" < that would be 47nF not 4,7nF. ; )


              • I know, that's what Edge has in his predator mod.....47nf or .047uf. I used .0047uf.
                You were asking how to apply the mod to the 22h
                So I gave the component #s for the 22h that are the equivalent to the 50h posted in Edge's mod.

                Comment


                • k
                  käsebrot commented
                  Editing a comment

                  Yes, that was, what I have asked for.

                  Haven't known that you changed some values - so I thought, you have done the mod as it is and are happy with it.


                  No need to argue - thank you very much! : )


              • It seems like adding a pot in line with r42 would have a similar effect as changing r42's resistance. That's weird. I might try messing with the "fizz" cap that you mentioned.

                I DID use .047uf in c2. I checked my notes and I was mistaken. The only deviation I made from the predator mod posted was lifting the leg of c6. I haven't noticed an increase in super flubby low end or hi fizz. So maybe some of the other component changes counteract the use of such a big cap in c2.
                Maybe Edge would chime in? It's his baby lol.

                Comment


                • So I've been messing with some values on my jca100h ...

                  After the predator mod, the OD channel is definitely brighter than the normal channel

                  So I either need to make OD less bright or add some bite to the normal channel. I think the latter is my preference because taking away brightness from OD(lowering or removing treble cap) also makes the low end flubby and round.

                  So my question is, what do I do to add some bite to the normal channel? Any ideas. I'm happy with the OD channel as is right now.

                  Comment


                  • Soulcrusher_X
                    Soulcrusher_X commented
                    Editing a comment

                    Motocooney wrote:
                    So I've been messing with some values on my jca100h ...

                    After the predator mod, the OD channel is definitely brighter than the normal channel

                    So I either need to make OD less bright or add some bite to the normal channel. I think the latter is my preference because taking away brightness from OD(lowering or removing treble cap) also makes the low end flubby and round.

                    So my question is, what do I do to add some bite to the normal channel? Any ideas. I'm happy with the OD channel as is right now.

                    Do you want more brightness? Or brightness and gain? You could bypass the normal gain control with a 250p-470p cap to add some brightness. You could also bypass R45 with a .47uf-1uf for some bite AND gain. In both situations, the smaller the cap, the less bass you bring into the signal.

                    Or put them both on toggles for when you need them or not.


                • So I wired up the clean crunch switch and get little effect. Also it affects both channels. I think I may be running the crunch channel too hot to get it to clean up

                  Could I use a different value for the resistor on The switch? What's the purpose of the 39k resistor to ground and why is it tied in to c30?

                  Comment













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