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

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  • I think my normal channel has too much gain going on right now.

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    • Just discovered a pretty sweet mid boost by accident

      Running .1uf in parallel to c14.
      I just put it on a spst toggle right next to the normal preamp knob.
      It's pretty awesome. It adds upper mids and definitely adds some Marshall to the tone.

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      • This is on the jca100h board.

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        • So for the mid boost, .1uf is a bit much. I settled on .001uf. It adds some nice upper mids and highs. Not brightness though. Seems to really open everything up a bit.
          Also I replaced c21 with 100pf and ran a .001uf to a toggle.
          This is because the OD channels tone seems to change quite a bit when you change the normal channel's gain setting.

          It's like a bright/highs switch for the lead channel only.

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          • The thing I don't quite understand is why messing with c14( which seems to be the treble cap) affects mids more than highs?

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            • Soulcrusher_X
              Soulcrusher_X commented
              Editing a comment
              If the gain knobs are anything like the SLO, then they are fairly interactive with each other, and you may find the two channels "blend" with each other a bit.

              The treble cap changes where the treble knob interacts with the tone. It typically determines the treble's "lower range" so with this particular tone stack, it's interaction is mostly around 1.5khz and higher, which is well into "midrange territory". If you increase the size, it rolls off treble at even lower frequencies. If you decrease it, you reduce the midrange and leave high treble. Some high gain amps that are brighter have values around 220p for the treble cap. A lot of VHT amps use this value for the treble cap and 56k for the slope resistor and I would say they are brighter than the SLO/JCA for sure.

          • Hmmm ...well I'm realized that the mid boost doesn't need to be on a switch because it just sounds better with it ON. Lol.

            I may leave my 100h as is...for now
            But I'm thinking About starting over with the 22h
            I'd like to try the SLO preamp mod as well.

            I also don't like the idea of leaving components out of the mix.
            Soulcrusher, what would you recommend? For c28 and r19?

            For a metal sounding 22, I would highly recommend starting with the predator mod. I listed the values on the previous page. Give it a shot

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            • One more question for Soulcrusher...would u mind taking a look at the schems for the 50 and 22...C20 on the 22 is what cap on the 50?

              I raised the value on my 22 and it really smoothed out the fizzy brittle highs. I'd like to do the same on my 100 but can't figure it out lol

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              • third_eye
                third_eye commented
                Editing a comment

                sorry for sounding like a dumbass but i have no idea what do do....
                could someone perhaps simplify it and give me instructions?


              • Soulcrusher_X
                Soulcrusher_X commented
                Editing a comment

                Motocooney wrote:
                One more question for Soulcrusher...would u mind taking a look at the schems for the 50 and 22...C20 on the 22 is what cap on the 50?

                I raised the value on my 22 and it really smoothed out the fizzy brittle highs. I'd like to do the same on my 100 but can't figure it out lol

                Do you want to know for the 50 or the 100? I don't have the power section scheme for the 50, but on the 100, it's unlabelled. Looks like it should be C12, though. Another thing to experiment with to rid some fizzies is to bypass the two anode resistors of the PI with small caps. A lot of Mesa/Boogies do this also to stabilse the output sections of their amps. The two PI anode resistors are R35/R36 for the 22H and R9/R10 for the 100H. Something small like 75p or 120p should be plenty...BUT like you know....once the mod bug bites....you're going to swap til you find what works lol.

                 

                For these small bypass caps or the treble cap, some high voltage ceramics will be just fine. Like mentioned before, the silvered micas and ceramics tend to sound VERY similar but the ceramics are less than 1/10th the price of the silvered micas. Ceramics CAN sound gritty at higher voltages, though. Not a bad thing, though. They can add texture when put // with poly types. (Mallory 150s and Sprague/Mallory Orange drops).


            • Hey all.
              I have an idea but I'm not sure how to wire it up.
              I already have the treble cap(c14) on a Spst toggle with a .001uf cap in parallel with the stock 470pf.

              Now I'd like to somehow wire a toggle to the slope resistor(c24 on the 50/100 and c26 on the 22)
              So I can switch between the stock value 47k, 39k and 54k. Seems like the options for tweaking tones would be endless

              So how would I wire this? I'm new to the toggle switch thing.

              My other thought is to just replace the slope resistor with a 100k pot. Would this work? What type of pot would I need?

              Thanks!!!!!

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              • Motocooney
                Motocooney commented
                Editing a comment

                I'm messing with the Tonestack calculator.

                I'm using the Marshall style not the Fender style stack.Is that right?

                The jca uses a cathode follower fed tonestack right?

                I'm wondering if changing up some of the pot values mmight be cool. Or would I get the same effect by messing with the individual tone caps (treble bass and mid) or just the slope resistor.

                Awe **************** this getting confusing and overwhelming and awesome lol


            • For the tone stack calculator, what is Zsrc? The default Marshall value is 100k.
              Also, r5 is 570k. What resistor is this on the jca? Is it a pot?
              Thanks.

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              • I've been getting most small caps at ****************ty radio shack just cause its 5 minutes away. I have ordered from mouser though. Just hate waiting for parts to arrive. I have no patience.

                When I enter 1m for r5 the waveform just drops all the way to the bottom ?

                Comment


                • k
                  käsebrot commented
                  Editing a comment

                  To get the Soldano/Jet City tone stack, just change R1 to 47k and R5 to 1M.

                  Please try it again, the wave won't be dropped down to a flat line.


                  If you want to change something in the EQ, try another slope resistor and treble cap values. And maybe change the mid pot to 50k lin..

                  I've just put in a 2,2uF cap instead of the 1uF at C8 (JCA22H). Don't like the sound at all, seems to boost the bass, increases gain and makes the amp overall very muddy and flubby sounding - even while having only 4,7nF at C2. Can't recommend it. If you want more bass, then put in a 33nF at C19 (cap to the PI) and/or 33uF at C23 and C24 (caps in the PI).


                  I don't know, what the other changes of the resistors R5,R9 and R18 might do - and it seems, the user called Edged would explain that.


                  Maybe, the stock version sounds best, just with a few changes like lowering C2 to 4,7nF and C7 to 220pF and put in better tubes and caps.


                  I also don't like all these fizzy BFG clips. I have no idea what brian does on the 22H, he also doesn't response to queries about that. Ok, it's his secret and he want to earn money with his mods.


                  But maybe Mike Soldano also knows what he does when creating the 22H.


              • Man - you guys have gotten busy! This is all really great stuff, and totally inspiring me to start modding my JCA again. Keep up the great work!

                Come join us at the NEW Jet City Lounge on guitarampboard.com: http://www.guitarampboard.com/forum/...php?f=5&t=1615

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                • ****************. It seems I now have two OD channels. Lol sounds righteous though. I don't care for bfg clips either.
                  Mine sounds better......and I haven't a clue what I'm doing0

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                  • I was looking for c20(jca22) on the 100. Sorry did I say 50? Lol. But correct me if I'm wrong, the 50 and 100 boards/components/values are the same? I guess the power section is different but it is it?

                    Well, I played my 100 at full band practice tonight.... I'm not overwhelmed by awesomeness like I thought I would be.
                    The normal channel now sounds like the OD channel but better. It's perfect. But the OD channel sounds flubby and harsh at the same time when playing anything but singy leads.

                    I might put the OD preamp back to stock and start over. It's just kind of disappointing. It sounded badass in my basement. Lol.

                    I just want a tight big low end with smooth highs and mids. I want palm muted stuff to chug without having a metal tone.
                    But also lead work to sing and cut through...without being overly bright.
                    Am I Asking too much out of this thing?

                    I just should've kept my uberschall. Daycare is expensive though lol.

                    I'm now open to ALL suggestions for how to make the OD channel into something amazing.

                    Comment


                    • Soulcrusher_X
                      Soulcrusher_X commented
                      Editing a comment

                      Motocooney wrote:
                      I was looking for c20(jca22) on the 100. Sorry did I say 50? Lol. But correct me if I'm wrong, the 50 and 100 boards/components/values are the same? I guess the power section is different but it is it?

                      Well, I played my 100 at full band practice tonight.... I'm not overwhelmed by awesomeness like I thought I would be.
                      The normal channel now sounds like the OD channel but better. It's perfect. But the OD channel sounds flubby and harsh at the same time when playing anything but singy leads.

                      I might put the OD preamp back to stock and start over. It's just kind of disappointing. It sounded badass in my basement. Lol.

                      I just want a tight big low end with smooth highs and mids. I want palm muted stuff to chug without having a metal tone.
                      But also lead work to sing and cut through...without being overly bright.
                      Am I Asking too much out of this thing?

                      I just should've kept my uberschall. Daycare is expensive though lol.

                      I'm now open to ALL suggestions for how to make the OD channel into something amazing.

                      I hear you on daycare, brother. I have three lol. Sold my Splawns, my SLO Clone and MarkIII to keep up with the kids. Good thing they are cute. lol Anyway, what did you do to the OD channel so far? Let's so backwards and see how to get you back where you want to be. The SLO mod is definitely a step in the right direction. I'm basing all of my suggestions on my old SLO clones. I still have yet to try the JCA versions. I'm waiting to find one at a screaming deal so I can join the mod party.

                      What speakers/tubes/guitar/pickups are you using?

                       

                      Try this: put a 15k resistor // to R32 (or change R32 to 10-15k). Add a .0033uf cap // to C27 (or change C27 to .0047uf). Change C32 to .68uf.  This should tighten the amp up and add some "Marshall" to the OD channel. Also, if you want to use FX pedals, add a 860r // to R25 and add a 4u7 cap // to R21. This will also stiffer up the tone a little bit and make the loop more pedal friendly.

                       

                      Oh, and when I put //, it means to put a component in parallel with another.


                  • As far as the OD channel, I have done "the predator mod" and the 4 changes that you listed above^^^^

                    Fixing the FX loop was super cool. So I'd like to keep that(I use an eq through the loop for solo boost)
                    I'm gonna tear it open tonight and take a look at what exactly I did in the last week. I went kinda crazy changing stuff out this weekend so I may have changed some components and not put it in my notebook. Lol

                    I think I might try the slo preamp. Just need to order some 500k pots.

                    Thanks for the help. I'll post exactly what I've done to it tonight.

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                    • I'm using an Egnater Tourmaster 412 with v30s
                      79 hardtail strat with hot rail in the bridge maple fretboard
                      Tele with hot rail in the bridge maple fretboard
                      Stock 6l6 power tubes
                      V1 hg, V2 tungsol ri, V3 ruby hg, V4 old Marshall wt42(not sure had it in my drawer), V5 Millard ri

                      Running bias at 36ish

                      Also I have a bright switch on c21. Replaced stock with 100p and have a .001uf in parallel.

                      Comment


                      • Soulcrusher_X
                        Soulcrusher_X commented
                        Editing a comment

                        Motocooney wrote:
                        I'm using an Egnater Tourmaster 412 with v30s
                        79 hardtail strat with hot rail in the bridge maple fretboard
                        Tele with hot rail in the bridge maple fretboard
                        Stock 6l6 power tubes
                        V1 hg, V2 tungsol ri, V3 ruby hg, V4 old Marshall wt42(not sure had it in my drawer), V5 Millard ri

                        Running bias at 36ish

                        Also I have a bright switch on c21. Replaced stock with 100p and have a .001uf in parallel.

                        Do you know what kind of 6L6s are in your amp? Oh, and which 4 mods did you do? I lost track of how many I listed. lol Have you tried different combinations of tubes in your preamp?













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