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Jca50H / 100h/ 22h mod thread and owners club

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  • As for the C19 modification that I have proposed and the problem mentioned by "Pandemic 2", there is no leakage from the lead to the clean. But: as the effect is lowering the gain of both channels you might notice differences in the relative levels of the channels. The mods bring back some "old-style" feeling of (good) marshalls amps, the amps responds better to pick attack (more dynamic).
    Another good mod is the slope resistor (I like 68k here), to lose some of the excessive low-mids these amps have.
    This will reduce the gain also of both channels, allowing to push the master a bit more (good). You can compensate it by increasing the plate resistor of 4stage to 220K like the slo100 (stock JCA is 100K).

    Now, The leakage problem.
    In my amp (stock version, no mods) the lead channel was also bleeding into the clean.
    I found out that there was a bad soldering in the footswitch connector. A bad solder there means that less current is going to the LDRs and you might have malfunctions. If everything looks OK, the problem might come from a bad LDR, or from the switching circuit.


    • Anybody see the new custom 22 ? looks dope!
      Quality Tube Guitar Amplifiers. Designed in Seattle by legendary boutique tube amp builder Michael Soldano and built affordably from high-quality materials.


      • bump


        • Shinigami75
          Shinigami75 commented
          Editing a comment
          Hi there, I've got a Custom 22


        I'll just leave this here :-)

        That's basically what they are, yeah?


        • I am so confused by the hovercraft site.. I would like to go and view the amps but its too much like reading a friggin book for me.

          I need a 2 channel amp with 2 EL84's hopefully around 15-20 watts, some nice voxey cleans or some other sort of shimmery clean tones , and a nice mid to high-ish gain channel that sounds like a modded JCM800. A tube effects loop would be great. no reverb, no extra shti. It has to take pedals like a hooker takes meat shafts.
          Last edited by mesa3077boogie; 12-15-2015, 12:35 AM.


          • Hey everyone
            I've bought jca50h yeasterday and I'm realy happy) Finaly my setup is stereo
            I want to change tubes but first i want to ask you guys about your opinion.

            My curent rig: fender tele (sd blackwinter), engl blackmore (jj 6l6), DL412pro v30. Od808 for boost and couple effects in fx loop. Tone is bright, and sharp, realy punchy.
            For Jet City I've got 1960a but I thinking about 212 from DL with creambacks. I think that I'm serching for rounded and little darker tone to fill Engl sound.

            first, I will do slo mod and depth mod
            second, I will change power tubes, so I could put almost new GT6L6R for cheap option or buy new JJ. Maybe something else??
            then i will try new preamp tubes. And it will be greate if you could recomend me something. I was thinking about electro harmonix 12ax7 or JJ ecc803 (low noise)for v1 and v2 and 12at7 for v5 rest eec83 JJ

            so, What tubes are you recomending? what tubes have you used?

            Last edited by etah; 06-04-2016, 07:00 AM.


            • Click image for larger version

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              Hi Everyone,

              I bought a JCA100HDM a week ago. Newest model with the Jet City front panel and Presence and Depth knobs. It was a stupid deal of the day for $499.00 delivered
              My first mod was to replace all the tubes. (4) Ruby 6L6GCBSTR matched set and (5) Ruby 12AX7AC5HG+.
              Amazing difference. The HG+ are the premium quiet version of the medium gain tubes. I have a set in my Panama Inferno and they work really well there.
              Then I did the SLO 100 mod with Warren Haynes and Bright switches.
              I used to own a 1991 SLO100 and this is very close. I've only done a preliminary test but I'm digging the amp.
              Loud as Fu@k like a SLO but it only goes to 9, not 11.
              It has the SLO100 vibe and is close after this mod for 1/8 the price.
              Bias is set at 41.6ma.

              I removed the blue LED in the middle of the amp...useless.....

              Here are the updated and corrected parts list for the Mouser parts and the pots. The old lists need updating.
              These are direct replacements and the pots are an exact match. current parts

              (2) 71-CCF60-475K-E3 Vishay Metal Film Resistors 475K ½ watt R41 & R42
              75-562RSTSD022 Vishay Ceramic Disc Capacitor 500volts 2200Pf C27
              594-D102K25Y5PL63L6R Vishay Ceramic Disc Capacitor 500volts 1000Pf C21
              (1) 71-CCF60-221K-E3 Vishay Metal Film Resistors 221K ½ watt R19
              598-715P47356LD3Cornell Dubilier Film Capacitor 600Volts 47000pF ORANGE DROP C10 & C11
              (1) 594-D471K20Y5PL63L6R Vishay Ceramic Disc Capacitor 500 volts 470PF C28
              506-A101SYCQ04 TE Connectivity Toggle Switches


              (2) P-V500KA-M16S Pot, 500K Audio, Short Shaft, 16mm
              Attached Files
              Last edited by spunky9999; 10-11-2016, 09:59 PM.


              • I just came here to show off the mod i've done on my JCA50h, and I don't believe there's any talk of this on this topic.
                I added a sweep pot (like on krank amps). It was a nice guy on the Official JC group facebook page that told me how to do it.
                For the metal-heads like myself it tightens up the amp a fair bit, you can go from a boatload of mids to very scooped. Anyways I'm loving it, if anything i'd say it"s more important on the "to do" list than the depth mod, and equally as easy to do !
                On a 50/100h you just have to replace the r24 resistor with a 100k linear pot, on a 22h it's r26 that needs to be replace with the pot and on a 20h it's r21.

                Anyways here's a quick video I did.

                Boost : MXR M77 od in front.
                Pickups : BKP WARPIG alnico V
                Cab : jca24S+ with V30
                Mic : Tbone MB75
                Last edited by mochi; 03-10-2018, 09:17 AM.