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  • Marshall JMP-1 Preamp Tubes

    I pulled out the stock Marshall tubes last night and put in some
    Electro Harmonix 12AX7's.

    OH my....

    Not sure if those stock tubes were just old or if they really sounded inherently bad, either way it sounds amazing now.

    Anyone who says the tubes aren't doing anything in the JMP-1 is full of crap. If the tubes really weren't doing anything I suspect changing them wouldn't make much of a difference.

    Looking at the JMP-1 schematic: there IS a diode clipper in there, but it doesn't even start clipping until the signal at that point hits about 2.1V (about 3 diode drops). The tube is doing the magic up until then.

    Anyway, I digress....

    These new tubes made a huge difference in the tone of the preamp. What was once somewhat harsh sounding distortion is now super-smooth, and more focused.

    I had to tweek the EQ a bit since the new tubes affected the high-
    end, but I'm much happier with the overall sound of it now.

    I'm buying some JJ's tubes tonight after work. I'll try them out
    this weekend as well. I've heard good things about JJ's in the JMP-1.

    Jason
    stilwel

  • #2
    Let me know which tubes sound the smoothest in yours. I wanna change my stock tubes out.
    New song "Winnie Cooper" by Leave Her Crying! Only $0.99!
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    • #3
      Originally posted by stilwel

      Anyone who says the tubes aren't doing anything in the JMP-1 is full of crap. If the tubes really weren't doing anything I suspect changing them wouldn't make much of a difference.

      Looking at the JMP-1 schematic: there IS a diode clipper in there, but it doesn't even start clipping until the signal at that point hits about 2.1V (about 3 diode drops). The tube is doing the magic up until then.



      Gee why do you need a SS clipper at all?? I mean I could understand having a boost switch that engages clippng diodes more dirt for tones that require more than the 4 gain stages provided by 2 dual triodes(which btw is quite a bit of gain)But theses diodes are voltage dependant and always in the circuit!Plus the tubes I'm pretty sure are used in parallel not series.The JMP-1 is pretty much a Valvestate preamp.


      It SUX






      Yo Billy wassup?

      Comment


      • #4
        The tube stages are in series. One tube is used for the OD channels, the other tube is for the clean channels.


        This has been discussed to death, so I won't comment on it anymore.


        I have the JJ tubes in hand. I'll try them out sometime this weekend and give full report of EH vs JJ 12AX7's.

        jason
        stilwel

        Comment


        • #5
          Hey stilwel,

          Thanks for the info! Definitely let us know how you like the JJ's versus the EH's. Some time ago I read where one guy had tried a JJ ECC83 in V1 socket and a JAN GE12AX7 in V2 socket, and that sounded really good. I've been meaning to give that combo a try some time.

          Comment


          • #6
            Originally posted by stilwel
            The tube stages are in series. One tube is used for the OD channels, the other tube is for the clean channels.


            This has been discussed to death, so I won't comment on it anymore.


            I have the JJ tubes in hand. I'll try them out sometime this weekend and give full report of EH vs JJ 12AX7's.

            jason


            By your description thats PARALLEL operation and is exactly also how I was informed of thier function so it was correct.

            LOL! If you are going to contribute to a forum in a credible fashion it helps to know the difference.

            Comment


            • #7
              Originally posted by Soldano67


              By your description thats PARALLEL operation and is exactly also how I was informed of thier function so it was correct.

              LOL! If you are going to contribute to a forum in a credible fashion it helps to know the difference.


              Laugh all you want....but where is YOUR Electrical Engineering degree from??

              Mine is from Purdue University.

              By MY description I said that one tube was dedicated to each channel. Each tube has 2 stages. These 2 stages are run in series. If you can read a schematic it's very clear they are not run in parallel.

              Anyway this thread was about how much a tube change influenced the tone of the preamp, dramatically in this case.

              out
              jason
              stilwel

              Comment


              • #8
                Originally posted by stilwel


                Laugh all you want....but where is YOUR Electrical Engineering degree from??

                Mine is from Purdue University.

                By MY description I said that one tube was dedicated to each channel. Each tube has 2 stages. These 2 stages are run in series. If you can read a schematic it's very clear they are not run in parallel.

                Anyway this thread was about how much a tube change influenced the tone of the preamp, dramatically in this case.

                out
                jason


                Your description was basic and describes the use of the tubes as being parallel -ie, each tube works independantly for clean and dirty.Thats all that is required.

                Tubes is the subject NOT the individual triodes.

                Jason, life is too short to be a wanker especialy a pretentious one so quit while your ahead.

                Stupid troll

                Comment


                • #9
                  Originally posted by Soldano67


                  Your description was basic and describes the use of the tubes as being parallel -ie, each tube works independantly for clean and dirty.Thats all that is required.

                  Tubes is the subject NOT the individual triodes.

                  Jason, life is too short to be a wanker especialy a pretentious one so quit while your ahead.

                  Stupid troll


                  ...I'm the troll???

                  If you look at the top of the page, I started this friggin' thread.

                  You've successfully hijacked it off-topic.....well done.


                  .... enough of this nonsense. I have tubes to try out in my JMP-1.
                  stilwel

                  Comment


                  • #10
                    Originally posted by stilwel


                    ...I'm the troll???

                    If you look at the top of the page, I started this friggin' thread.

                    You've successfully hijacked it off-topic.....well done.


                    .... enough of this nonsense. I have tubes to try out in my JMP-1.



                    Ya the sad part is you became a troll in your own post lol

                    Off topic? mm not very far off since you and I have established once and for all that the JMP-1 uses its 2 tubes in a parallel configuration.It means that all the distrortion the preamp generates after a mild overdrive(1 tube) is all diode clipping, this is very significant.It means that the tube has very little effect on tone regardless of the quality of the tube.

                    This also means the JMP-1 is a Valvestate design and my accusation that Jimmy at Marshall has been misleading consumers for over decade that its a tube preamp has been validated-again.You cannot get decent overdriven Marshall sounds from one tube its impossible.It should've been a "budget"
                    piece of gear not the $1000 compete with a Tri Axis "pro" gear preamp.

                    Jim Marshall you are a huckster ****************************.I mean the way you duped my good friend Billy Corgan is unforgivable

                    Comment


                    • #11
                      Originally posted by stilwel
                      The tube stages are in series. One tube is used for the OD channels, the other tube is for the clean channels.


                      aha. I've been meaning to ask about this for some time as I will definately be changing my tubes eventually. So which one is for which channel?

                      and i can't wait to hear about the tubes :

                      Comment


                      • #12
                        Hey Soldano why are you so anti JMP-1?

                        If you don't like it then that's fair enough, but you should try to make sure it doesn't take over your life.( don't take it so personal, calling people names isn't big or clever. )

                        We'd all like nice expensive boutique preamps but can't all afford it. At the end of the day if you own one of these( like thousands of others) and you like it then that's all that matters.

                        I'm not that technically minded but if the valves do nothing what are they in there for, and why does changing them make a difference to the sound.

                        I'd like a Triaxis but over here in the UK they are nearly four times the cost of the JMP. Are they four times better ? Perhaps they are.

                        Comment


                        • #13
                          Originally posted by sp_spaceboy


                          aha. I've been meaning to ask about this for some time as I will definately be changing my tubes eventually. So which one is for which channel?

                          and i can't wait to hear about the tubes :
                          stilwel

                          Comment


                          • #14
                            Originally posted by Driftone
                            Hey Soldano why are you so anti JMP-1?

                            If you don't like it then that's fair enough, but you should try to make sure it doesn't take over your life.( don't take it so personal, calling people names isn't big or clever. )

                            We'd all like nice expensive boutique preamps but can't all afford it. At the end of the day if you own one of these( like thousands of others) and you like it then that's all that matters.

                            I'm not that technically minded but if the valves do nothing what are they in there for, and why does changing them make a difference to the sound.

                            I'd like a Triaxis but over here in the UK they are nearly four times the cost of the JMP. Are they four times better ? Perhaps they are.


                            Hey Drift I understand your point but just keep in mind stilwel says he is an electrical engineer as a way to add credibiltiy to his point even though he knew he was wrong about a pretty basic concept-then tries to say "well what I really meant was.....". He opened himself up for a lil abuse

                            You have to remember that in America the Mesa Boogie Tri-Axis is about 1500 full retail(people paid less too)The JMP-1 was $1000 new.The Mesa is a 100% tube preamp that uses multiple(5) tubes in a series configuration to get overdrive,just like a regular amp preamp would.Its signal path is 100% tube and uses no SS to assist in clipping or buffering.

                            The JMP-1 Well I've already covered it,Its a hybrid which owes most of its tone to the chips and diodes it has.Marshall calls it a "tube preamp" which while accurate doesnt tell the true story its a half truth-used cars salesman truth.

                            The JMP-1 sounds and responds like a refined distortion pedal.The Mesa responds like a tube amp, very organic.

                            The JMP-1 is worth to me $500 new which I think it is in the UK 500 pounds.

                            Not only is it a poor concept it failed in execution Jim makes it worse by "making a pitch" and charging way more than its worth.He burned alot of suckers.

                            All other "tube" midi preamps use the tubes in series to generate distortion (with the exception of the rocktron Pirhana, its like the JMP-1 and sounds like trash too) and generate a "genuine" sound.

                            Jim has never made a worthy tube preamp ever.His first-the 9000- had 3 tubes and was all tube but it was a bit wierd and the lead channel while having alot of gain was voiced oddly.subsequently thta preamp gets mentioned by no one and people have to give them away on eBay.Then he makes a Hybrid midi preamp(JMP-1) and while it has great feaures and lay out the sound and feel really bites.

                            Comment


                            • pmag55
                              pmag55 commented
                              Editing a comment

                              I know I'm about ten years (at least) too late to contribute,  but explain your scientific theory to Adrian Smith and Dave murray Mr. tube tone axpert!!.Go flush your opinions down the toilet, as that's where they belong, you laughable idiot.


                          • #15
                            Mine responds like a tube amp when my power amp is cranked on stage. It sounds so much better than my friend's modded JCM 800 and it's 10000000 times more versatile. I don't care if it's "all tube" or not. I like it and people compliment my tone. Marshall must've done something right to have so many famous people using the unit.
                            New song "Winnie Cooper" by Leave Her Crying! Only $0.99!
                            http://www.cdbaby.com/cd/leavehercrying

                            Great HC Transactions - Erock503, Rat83, JimAnsell

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