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  • #76
    Found a local electronics store that had some of what I need, and they suggested some capacitor substitutions - will the following work ok?



    Clean/Crunch Switch: 470pf 100volt multilayer ceramic cap - substituted for silver mica



    Depth Knob: .0047uf 400volt mylar/film cap - substituted for orange drop



    What voltage ratings for the 22uf electrolytic (Fender Bypass) and the .001uf ceramic (scoop mod)?



    Also, you mention polarity on the Fender Bypass - positive on the tube side of the 220k resistor, right?
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    • #77






      Quote Originally Posted by GRIMESPACE
      View Post

      Found a local electronics store that had some of what I need, and they suggested some capacitor substitutions - will the following work ok?



      Clean/Crunch Switch: 470pf 100volt multilayer ceramic cap - substituted for silver mica



      Depth Knob: .0047uf 400volt mylar/film cap - substituted for orange drop



      What voltage ratings for the 22uf electrolytic (Fender Bypass) and the .001uf ceramic (scoop mod)?



      Also, you mention polarity on the Fender Bypass - positive on the tube side of the 220k resistor, right?




      22uf is 50v or more.

      the .001uf is 1kv (most common value) also for the clean crunch cap go more than 100volts.

      You should recheck the instructions for that mod, the 22uf is a CATHODE BYPASS CAPACITOR. it bypasses r45 which has a value of 2.2k not 220k.
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      • #78
        You're absolutely right - my bad - R45 definitely is a 2.2k. Am I right about the polarity of the cathode bypass capacitor, though? Positive on the tube side / negative on the ground side of the resistor?



        Do you think the cap substitutions I listed going to be ok?
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        • #79
          cap substitution is alright as long as the silver mica cap is 400v and the orange drop is as well.

          positive to the tube side negative to the ground side.
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          • #80
            I recorded some clips this weekend. I did scoop mod with neck pick up on clean. It's my first time playing around with recording, does any one have any recording tips?
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            • #81






              Quote Originally Posted by Edge11
              View Post

              I recorded some clips this weekend. I did scoop mod with neck pick up on clean. It's my first time playing around with recording, does any one have any recording tips?




              Mac or PC? Garage Band works good for me, and I've heard good things about Reaper for the PC. What interface do you have?
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              • #82






                Quote Originally Posted by GRIMESPACE
                View Post

                Mac or PC? Garage Band works good for me, and I've heard good things about Reaper for the PC. What interface do you have?




                Pc using reaper. sm57 to lexicon omega.
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                • #83
                  Just posted up the "predator mod". it's the natural evolution of the "sucker punch mod" Makes the whole amp more aggressive. Tighter bass and more aggressive gain on both channels.
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                  • #84






                    Quote Originally Posted by Edge11
                    View Post

                    Just posted up the "predator mod". it's the natural evolution of the "sucker punch mod" Makes the whole amp more aggressive. Tighter bass and more aggressive gain on both channels.




                    Very cool - definitely gonna check it out. So at this point, have you decided which you like better between the 20 & 50?



                    Did you have any luck with recording? I just downloaded Reaper to give it a try. I'm using an M-Audio Fast Track Pro with Garage Band and it was pretty straightforward to get going - only problem for me is my SM57 that I've had in a box for the last 10+ years isn't working. Gonna have to get that fixed. I wish I could be more help with that.



                    Keep up the great work!
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                    • #85
                      Haven't had the time to record. I've been pulling 12 hour shifts at school.
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                      • #86
                        Holy ****************!!!



                        Just put the depth control together



                        Kick ASS!!!!!!!!!!!!







                        Massive body to the sound - all I've heard is that it affects the low end - I had the thing dialed up to 5 on the master, and it hits it all the way!!!!!



                        Did I say holy **************** yet?
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                        • #87






                          Quote Originally Posted by GRIMESPACE
                          View Post

                          Holy ****************!!!



                          Just put the depth control together



                          Kick ASS!!!!!!!!!!!!







                          Massive body to the sound - all I've heard is that it affects the low end - I had the thing dialed up to 5 on the master, and it hits it all the way!!!!!



                          Did I say holy **************** yet?




                          Good, good.

                          Now do some more mods
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                          • #88






                            Quote Originally Posted by Edge11
                            View Post

                            Good, good.

                            Now do some more mods




                            Actually had a bunch lined up today, but more questions came about...



                            I've researched what I could about discharging the caps, and built a resistor drain (470 ohm resistor soldered & shrink-wrapped in the middle of a jumper wire). I probed around pin 1 & 6 of V1 (it appears that both of these are plates), and realized that I hadn't seen anything about whether or not the tubes should be left in during this step - I had taken them out so they would be safe while I was taking the chassis out of the headshell & flipping it over. After watching the video again and looking over the schematic, I'm thinking they do need to be in, but I have not way of verifying that what I'm doing is right. What's the correct procedure - tubes in or out? Is there some way I can probe voltage to make sure I've got it drained? It looks like R1 & R2 are connected to the bigger filter caps - can I check there?



                            Also, you said something about taking the board out to do your desoldering / soldering. After removing the nuts from the pots and pulling about 12 screws holding the board down, I've concluded that it also means pulling all the jacks off the back panel and possibly desoldering wires off the small transformer (or is it a choke?). How did you go about pulling the board out without major surgery?



                            Thanks
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                            • #89
                              This is probably already in this tread and but I am wanting just straight forward instructions for a beginner wanting to add the depth mod to my JCA50h. I am new to this and am ready to begin modding my amp. this is the best thread ever.
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                              • #90






                                Quote Originally Posted by clay189
                                View Post

                                This is probably already in this tread and but I am wanting just straight forward instructions for a beginner wanting to add the depth mod to my JCA50h. I am new to this and am ready to begin modding my amp. this is the best thread ever.




                                Edge11 may beat me to this, but I'll try to put something up this week if he doesn't. Actually, he's covered it pretty extensively in the JCA 20H thread, but the NFB resistor is labeled differently.



                                Here's the basics along with some tips. It's only 2 components and some wire - a 1 meg audio taper pot and a .0047uf 400v orange drop cap. Hardest part was drilling the front panel (I wanted mine right next to the Presence knob, like the 100HDM) without dropping metal shavings into the chassis or running right through the filter caps, which are only about 5/8" from exactly where I placed the pot . I clamped a scrap piece of 5/8 wood on the inside where I was drilling so that my drill wouldn't punch through wildly, and was really careful about shavings. The pot basically gets inserted between the NFB (negative feedback) resistor and the 4 ohm output at the back panel. There's a red wire going to the pcb (pad label: FB) that I desoldered from the output jack and ran to the front panel where the new pot was being installed. A new wire was put in from the output jack to the other lug on the pot, and voila - done.



                                Well worth the effort, in my opinion. As I said, I'll try to put something better together soon.
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