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2963 Views 12 Replies Latest reply: Jun 19, 2010 4:07 PM by mtrash14 RSS
pikeral Just Startin'
pikeral
126 posts since
Feb 5, 2009
Currently Being Moderated

Jun 13, 2010 11:46 AM

A couple mods

Hey guy's i wanted to share some info on a couple mods. I know some of you have done these already. I have to put in my two ¢. I did Mtrash's mustard cap mod on friday, Holy Friggin Crap. The change is amazing. My 212 sounds amazingly smooth, nice tight bottom end and clean high's. When you play chord's every note is crystal clear, great definition from clean to insane. The overall tone has not changed, i didn't have to touch the EQ. I was running a .033 cap in C7 to cut back on the harsh treble and put the original value back in, .1uf. The presence is alot less harsh for sure but i still believe a lower value works better. I might have to go back a swap out the .1uf cap with a lower value but i am going to wait for the 100 hour break in period. I can't believe it's going to sound even better after the break in. IMO this mod bring's the SV to a new level of performance and is a must have. For the price of under $30 for the 212 it can't be beat and is worth every penny.

I did Space's bias point mod a couple of month's ago. Again IMO this is a must have mod. Three chassis jack's, two 10k linear pot's, a tiny bit of wire and some patience and a little skill, your good to go.

I picked up a green jewel and a red jewel, with the blue LED the red was very dim but with the green it worked out nicely, kind of like a sea blue or aqua i guess. keeper for sure. I bought a JJ803s and put it in the SVpre. Very nice tone, i'm sold on the 803 in that spot for good.

I must say thank's to all of you for sharing your mods and trick's, i couldn't of done this mod without you all. Cheer's. Here's some pic's of the finished job.

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  • sofnwhat Just Startin'
    sofnwhat
    687 posts since
    Jan 25, 2007
    Currently Being Moderated
    Jun 13, 2010 10:25 PM (in response to pikeral)
    Re: A couple mods

    Awesome man, thanks for sharing. I'm jealous, I really want to do Space's test point/bias mod. I've also been wanting to do MT's bass mod, and been thinking about doing the mustard caps too.

  • mtrash14 Iknowathingortwo
    mtrash14
    539 posts since
    Feb 18, 2009
    Currently Being Moderated
    Jun 15, 2010 4:57 PM (in response to pikeral)
    Re: A couple mods

    First I want to say Pike I've very proud of you.  You have taken a huge step here and working on your own - using your own skills - you have did these mods and did them completely safe inside a dangerous tube amplifier.  Good job man.   Two thumbs up for sure man.

     

     

    I'm a true believer in the external bias point mod.  IMO - any amp with internal bias adjustments is not user serviceable.  The external bias points makes checking the bias an easy and safe deal for anyone to do (within reason of course ).  I'm sold 100% on this bias mod.

     

    If you don't mind I would like to critique your mods a little.  First while looking at DSC02597.JPG  I would say that what I can see of your solder joints look very good.  I don't think you will ever have any trouble from them.  But I do think I would lead dress this mod a little differently.    First lets talk about the 2 reds and single black wires coming off the 3 prong test strip.  I would like to see these three wires neatly - tightly twisted all the way down to the solder joints up to the split from the center section.  This is hard for me to explain but make 90degree bends in the wires - group them together - then tightly twist them all the way up to the center then 90degree bend the 2 reds out to the end points.  I would also like to see simple slip on connectors onto the test strip studs so if you ever had to remove the tube section board they would simply unplug there.  This would easy to do and I think would make it look better to me.

     

    Next - the 2 groups of wires coming from the board to the 2 pots.  These need to be tightly twisted and formed into 90degree bends up-over-then out- to the pot.  They also need to be kept away from the OT wiring.  Any noise picked up there is going to be in the speakers in a big way.  You want to cross those wires at right-angles and not touch them.   You could also unplug the OT strip - neatly twist them up and replug.  This will give you more room and clearance.  These wires could be tied together up so high then split to two twisted groups going to the pots.  I would keep them away from the OT as far as I could.

     

    I can't say you are getting noise from these wires but I'm not seeing proper lead dress these here either.  I'm sure if you take a few minutes to look at this pic you will understand what I'm saying.  Neat lead dress is very much part of modding and amp building.  Hope I'm not crossing any lines here but I did want to say what I think the proper dress would be in this case. 

     

    I can't see it and I don't remember either - but I'd like to see the Bass Mod on there too.  I'm sure you would love it.  Its the best $2 I've ever spent.

     

    Again - Good job man, and I'm glad you're enjoying the mods.

     

    Later

    M^T

    • pikeral Just Startin'
      pikeral
      126 posts since
      Feb 5, 2009
      Currently Being Moderated
      Jun 15, 2010 6:18 PM (in response to mtrash14)
      Re: A couple mods

        Thanks guys. Trash no line crossed and criticism is most welcome for sure. I'm just learning so fire away, it only help's. I see what you mean about the dressing issue's. Going to have to fix that for sure. I'm not getting any noise through the speaker's, if anything the amp is quieter than it has ever been. I think for now i'll just unplug and twist up the OT wire's so nothing is making contact. The wire's coming off the test prong are a pain in the *** to connect to the chassis jack's. I tried to solder them but it didn't work out. I did the Bass mod a couple month's ago and i it's a keeper for sure. Thank's again...Cheer's                                   

      • mtrash14 Iknowathingortwo
        mtrash14
        539 posts since
        Feb 18, 2009
        Currently Being Moderated
        Jun 16, 2010 5:03 PM (in response to pikeral)
        Re: A couple mods

        Thanks Pike for not taking my advice wrongly.  I do mean well man and I only want to assist you guys if I can.

         

        Modding amps is fun and is also a learning experience.  Electronic knowledge you learn inside these amps is carried over to many other things we do these days and it does help us.  Proper lead dress is more of a cosmetic issue than a noise issue in this case.  Great amp builders and modders are very proud of their lead dress abilities and take much pride in their craftsmanship.  Besides looking right - proper lead dress makes for a long term mod that will stay with you where ever you may wind up playing because it will be right to begin with.  I can't say off the top of my head if noise can be picked up by these wires into the OT - but that is not the point I'm trying to make here.  I do hope you understand where I'm coming from.  Its the dress appearance that matters first, then the noise issue would be addressed if needed then.  I hope that makes sense too.    I know it sounds wierd the way I said it.

         

        We are all learning here as we go along and I hope you will remember that about me also.

         

        Agree:  The Bass Mod is my best work.  Its the biggest bang from the buck of anything I've come up with so far.  That mod I love indeed.

         

        BTW:  I just ordered some new tubes for my SV.  JJ6L6GC's and a couple new 803s tubes also.  I'll post how they do in there.

         

        Later guys

        M^T

    • spaceatl Expert Line 6 User
      spaceatl
      4,456 posts since
      Jan 24, 2007
      Currently Being Moderated
      Jun 16, 2010 10:39 PM (in response to mtrash14)
      Re: A couple mods

      I might spend $60 on the bass mod...Looking at the v-cap...There is a $30 alternative but not in teflon/copper...probably not worth it but my pics will look cool...

      • mtrash14 Iknowathingortwo
        mtrash14
        539 posts since
        Feb 18, 2009
        Currently Being Moderated
        Jun 17, 2010 8:11 PM (in response to spaceatl)
        Re: A couple mods

        Pike - thats the deal I went for.  They sent me that email too and gave me the gas so I ordered them last night.  I am sorry my KT66's didn't work (blew the heater fuse and ****** me off) because they sounded so good in there.  I'm hoping these JJ GC's sound as good!!!!!  I'm getting pretty tired of those Sov's I can't stand them anymore.    Too sterile sounding for me I think.

         

        Space - - a $60.00 bass mod?????  I don't understand what that would be but I'd love to have it I think.   I'll tell you guys what my experiments have made me think.  The 2.0 DSP is mid range heavy and it has a muddy bass and terrible ice pick highs in it too.  The cap mod fixes the tube section and will let it pass whatever tone the DSP gives it without modifying it (I feel the stock caps were robbing the tone out to some degree).  Pike's words "it opened it up" is exactly what I said too.  Its an upgrade, but not a true fix for that 2.0 DSP IMO.  The SVPre Bass Mod kicks the bass up.  I know a 330uF cap is really big and in real life is "a lot of bass boost" but when that goes through a mid-range heavy ice picking DSP it does help it overall to a great degree.  You can get rid of too much easily with the bass control but without the bass mod you can't crank it in, so that mod does work IMO very well.  The JFET mod I'm trying out now is not a fix either IMO.  I do have more tone and the amp does sound better especially when cranked.  The tone is up a lot but its not fixing my mid-heavy DSP like I wanted it too.  If I crank up the amp its fixed but I play at home at low volumes so I'm stuck again IMO.  I'm trying to think up a fix but since I can't reprogram the DSP I'm going to stuck in the end.

         

        I love my amp and it sounds great but its still not exactly there yet, at least to my ears.  But I can say this (and I think I'm pretty safe saying it too) It's close!!!

         

        Good luck

        M^T

        • spaceatl Expert Line 6 User
          spaceatl
          4,456 posts since
          Jan 24, 2007
          Currently Being Moderated
          Jun 18, 2010 8:51 AM (in response to mtrash14)
          Re: A couple mods

          take a look at the V-Cap...stupidly expensive, but iI am very curious as the material make sense to me...

          • mtrash14 Iknowathingortwo
            mtrash14
            539 posts since
            Feb 18, 2009
            Currently Being Moderated
            Jun 18, 2010 8:29 PM (in response to spaceatl)
            Re: A couple mods

            Space:

             

            I did look them up and I don't think they are suited for the Bass Mod.  Here's why:

             

            cuTF says: Recommended for signal coupling in tubed electronics

            TFTF says: are among the most coveted signal caps on   the market

            OIMP says: crossovers and as output couplers

             

            The Bass Mod requires an  Electrolytic capacitor in a value of 330uF (the value I used), not a signal coupling cap.  Signal coupling caps will not be available in anything near this value.  They are different indeed.

             

            Those caps looks really nice to try but I don't think you want one in the position of the bass mod as they won't do what the bass mod needs to happen there.

             

            You could try them in any coupling cap location you wanted (either on the SVPre or in the tube section of the main board) and I'm sure they will sound great, but sorry - not in the bass mod cathode bypass cap location.

             

            A signal coupling cap is like a DC blocker that allows the AC signal component to pass through it.  The high voltage DC of the tubes plates is blocked by the cap but the signal is allowed to pass through depending on the value of the cap.  A cap in the value of .1uF allows most all the guitar signal through without clipping part of it off, where a value like .0022uF clips most of the bass freqs and up into the midrange allowing only the upper freqs through, besides no high voltage DC.

             

            A electrolytic cap can be used as a cathode bypass cap.  The tubes cathode (ground) has a resistor that allows a certain amout of current from the plates to pass to ground  (very simply spoken here) but this resistor has some value of resistance to the overall signal.  A bypass cap allows the signal within the value of the cap to pretty freely pass to ground which in turn multiplies the gain of the tubes stage (again very simply spoken about here).  You would not want a signal cap in a cathode bypass location because it would not act like you think it should besides signal caps are not available in anything near 330uF like electrolytic caps are.  A value of 330uF allows the bass really boom on up in that gain stage. The rest of the signal is also allowed to boom but the bass really benefits from this value.  More or less its everything and more than what we can hear but the bass really comes up with a large value like this.  Fender uses a typical value of 25uF.  A typical signal cap is .022uF.  A lot smaller value indeed.

             

            Hope this helps.

             

            Good luck

            M^T

            • pikeral Just Startin'
              pikeral
              126 posts since
              Feb 5, 2009
              Currently Being Moderated
              Jun 19, 2010 8:52 AM (in response to mtrash14)
              Re: A couple mods

              Hey guy's, right now i am using a 220uf electrolytic cap for the bass mod. Is the 330uf better? If so i will swap it out. Oh yeah i almost forgot. I noticed the plate voltage went from 450 to 460volts from pin 3. Is this to be expected after installing the sozo cap's?

              • mtrash14 Iknowathingortwo
                mtrash14
                539 posts since
                Feb 18, 2009
                Currently Being Moderated
                Jun 19, 2010 4:07 PM (in response to pikeral)
                Re: A couple mods

                The difference between a 220uF and a 330uF bypass cap is probably minimal.  I didn't try both of them on my SVPre but I have tried both them on my JTM45 and although I could tell a slight increased bass from the 330uF it was only a small amount...... but a noticeable change.  That's why I just went with the 330uF on my SVPre.  I figured it needed all the clean bass it could get.

                 

                Your cap mod should not of changed the plate voltage on the power tubes, but I do recommend a rebias job after the install.  Its going to change the amp and my bias was out a tad with I put mine in, but I might of just tapped the onboard adjustments during the mod and knocked them out.  My best guess is your homes wall voltage is a little higher today than it was the other day.  A higher wall voltage is going to effect our PT's output voltage so higher at the wall means higher on the plates.  I'd check that first, but again higher plate voltages won't hurt it.  A higher plate voltage is just going to give you a little more clean headroom and a little more output - both a plus IMO so you're good as it is.  Actually the amp should sound a little better at 460 than at 450, but the difference is going to be very slight at best.  Jump it up to 480 and you would indeed hear the difference - and it would sound better IMO.  That is why my Volt Mod on V1 and V2 helps the tone so much.  It raised those plates from about 120 to 168+ and that was enough to hear and that higher voltage really does sound better IMO.  Besides - no classic amp I know of has such low plate voltages on V1 and the PI as my SV did.  Someday I want to get it over 200 because I know it will sound even better that it does now, and its a simple resistor switch out mod.  In my case I used 100k 1/2 watt resistors where I want to try even lower values.  Like 56K or whatever will give me over 200VDC on those plates.  I think without a resistor I could get 240 but that's a little higher than I would want.  I will do it when I get time again.

                 

                Good luck

                M^T

  • spaceatl Expert Line 6 User
    spaceatl
    4,456 posts since
    Jan 24, 2007
    Currently Being Moderated
    Jun 16, 2010 10:36 PM (in response to pikeral)
    Re: A couple mods

    Nice job on the mod...This amp really is well designed and easy to work on in my view...I really do think the larger wire type bias pots are more stable than the plastic minis and do not drift on vibration as much as those stock ones...My amp had sort of the drifty feel of an old Twin with old loose as bias pots in it...kind groovy some times...glad to share but I was not the first to do this mod on the SV...Can't remember the guy's handle but a really early adopter had a tech do his using Weber parts and he posted it here...I think that was the old forum...not the old old forum...LOL!

     

    I agree with MT...cleaning up the install is a good idea/ Strain relief wires with removable twist ties with signal pairs crossing at 90 angles. Twisted pairs on signal pairs protects the signal from inducted noise...This is good for power feeds and audio signal....It should last the lifetime of the amp...easy to repair now too...I have a few Litz harnesses made up...a whole lot more to do on that one as I amp planning to do the power also...but one day...

     

    I have been doing cap research since MT posted his and I think I have finally settled on several mustards, Molded Blues, "the Royal 67s mod"(gonna series to 700v rating...now where to fit them...) and a v-cap or two in. The chassis keeps out the electrostatic noise like the shield in a guitar lead. Another gitRound2it projects is to improve the farraday cage effect and replace the stock aluminum tape under the top with copper tape...Thanks for the inspiration MT.

     

    I gotta plan the work out a little...a little more value research...I am thinking about putting a toggle to get two presence caps...and also on the bass boost mod also...

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