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2465 Views 19 Replies Latest reply: Mar 12, 2010 3:19 PM by mtrash14 RSS
stevementzer Just Startin'
stevementzer
38 posts since
Apr 1, 2007
Currently Being Moderated

Mar 5, 2010 9:50 AM

Biasing your amp vs. the factory warranty

Here is a great question for line6 folks!

 

I am looking at replacing the tubes in my SV MKII 2x12....   I am familiar with how to bias tube amplifiers, but I am concerned that if *I* bias the amp, my warranty will be void. The fact that I have to remove the chassis to adjust the bias stinks of 'warranty void'...

 

So....   am I allowed to bias my amp?  Or am I required to take it into a line6 authorized repair center?

  • pixel2020 Just Startin'
    pixel2020
    19 posts since
    Jul 3, 2009
    Currently Being Moderated
    Mar 5, 2010 1:43 PM (in response to stevementzer)
    Re: Biasing your amp vs. the factory warranty
    • I do not think biasing your amp is not going to void the factory warranty. Take it to a service center for that type of thing if you have never done it before.
    • stevementzer Just Startin'
      stevementzer
      38 posts since
      Apr 1, 2007
      Currently Being Moderated
      Mar 5, 2010 1:57 PM (in response to pixel2020)
      Re: Biasing your amp vs. the factory warranty

      I have biased other amps before... but each manufacturer seems to take a different stance regarding biasing/servicing operations.

      • mtrash14 Iknowathingortwo
        mtrash14
        539 posts since
        Feb 18, 2009
        Currently Being Moderated
        Mar 5, 2010 4:10 PM (in response to stevementzer)
        Re: Biasing your amp vs. the factory warranty

        The warranty is pretty important on these amps because of the digital processor inside of them and I suggest you don't do anything that might jeopardize that warranty.  If the digital does go out you want it to be covered 100% and not on you.  Hopefully if it has a glitch it will blow within the first year and be covered, not after it and uncovered.  Don't blow the warranty, wait the year at least.

         

        I'm a fine one to say anything about this.  I blew off my warranty by installing the SVPre a long time ago

         

        This is in your best interest. I promise.

         

        Good luck

        M^T

  • ResAlien Just Startin'
    ResAlien
    86 posts since
    Jul 24, 2008
    Currently Being Moderated
    Mar 5, 2010 4:23 PM (in response to stevementzer)
    Re: Biasing your amp vs. the factory warranty

    I think it is kind of silly that biasing the amp would void the warranty, but given that you have to remove the chassis, this is probably true.

     

    I think it is a bit silly to expect your customers to take an amp to a service center, probably leave it for several days, and probably pay at least $50 service fee just to change tubes.  Changing / replacing tubes should be something that anyone can do, without having to take it somewhere or worry about voiding your warranty.

     

    The problem is that when you change tubes, more often than not, the bias needs to be adjusted - even if replacing them with the same type.   Therefore, I think biasing should be viewed as something that anyone should be able to do, without having to take it somewhere.

     

    <Beginning of Rant>

     

    This is basically just a short rant to say that the SV really should come stock with external test points and bias pots.  Period.  This is not a hard or expensive thing for a manufacturer to add.  There are several sub-$1000 amps that provide this capability.

     

    My conclusion: When I change my tubes, I will be checking / adjusting the bias myself, whether if voids the warranty or not.  I'm certainly not going to go without my amp for days/weeks and pay someone else for something that should be easy to do.

     

    <End of Rant>

  • pixel2020 Just Startin'
    pixel2020
    19 posts since
    Jul 3, 2009
    Currently Being Moderated
    Mar 6, 2010 5:55 AM (in response to stevementzer)
    Re: Biasing your amp vs. the factory warranty

    Honestly your not going to get much of a change by switching the power tubes, I say keep the power tubes and replace the pre-amp tubes. You should get a few years out of the power tubes, will get a better sound difference if you just switch the pre-amp tubes. Also if you bias after changing the power tubes, how is line 6 going link that to a fault some place else? Just do it and play stupid if you have to take it for warranty work, just say you took it to an amp tech to have them replaced and biased. The manual even says if you change the power tubes you need to re-bias so whatever. The service centers could care less if you take it in for warranty work and oh my these are not the stock tubes. You have every right to switch your tubes and line 6 can't say kiss off we wont honor the warranty for replacing something that needs to be replaced over time anyway. You think they would void the warranty if you switched a blown fuse? I think not.

    • ResAlien Just Startin'
      ResAlien
      86 posts since
      Jul 24, 2008
      Currently Being Moderated
      Mar 8, 2010 5:29 AM (in response to pixel2020)
      Re: Biasing your amp vs. the factory warranty

      In "normal" tube amps, changing power tubes makes a very noticeable difference in tone - very noticeable.  Now, maybe the way the SV power section is designed, it doesn't make as much of a difference as in a real tube amp, don't know - but I'm going to give it a try.  I had the same Sovtek 5881s as stock in an Egnater amp, and when I switched them out to TADs, it opened the amp up dramatically.

       

      There are no real "preamp tubes" in the SV - the 12AX7s are a phase inverter for the power tubes and an input driver for the power section.  These tubes have very little effect on the overall tone.

      • mtrash14 Iknowathingortwo
        mtrash14
        539 posts since
        Feb 18, 2009
        Currently Being Moderated
        Mar 9, 2010 2:26 AM (in response to ResAlien)
        Re: Biasing your amp vs. the factory warranty

        ResAlien wrote:


         

        There are no real "preamp tubes" in the SV - the 12AX7s are a phase inverter for the power tubes and an input driver for the power section.  These tubes have very little effect on the overall tone.

        The SV has a preamp tube.  It also has a PI tube.  Changing these tubes for other brands/kinds/etc does effect the tone of the amp (IMO).

         

        Changing the power tubes to other brands/types/etc also effects the tone (IMO) because it did in my amp.  It might not be as drastic a change as in some amps but different tubes can and does change the tone of my amp.

         

        Good luck

        M^T

         

        [edited by MT ]

        • ResAlien Just Startin'
          ResAlien
          86 posts since
          Jul 24, 2008
          Currently Being Moderated
          Mar 8, 2010 6:24 PM (in response to mtrash14)
          Re: Biasing your amp vs. the factory warranty

          No need to be a condenscending jerkweed.  I've changed out more tubes in more amps than a lot of people, and I know what different tubes can do to the tone.

           

          Neither of the two 12AX7s in the SV are "true" PREAMP tubes, in the sense that most people talk about preamp tubes when they talk about tube amps.  From the L6 FAQ:

           

          Q: What are the function of the 12AX7 tubes?

          A: V1 is the booster to the output tubes, V2 is the phase inverter for the output tubes.  When viewing the amplifier from the back, V1 is on the left side.

           

           

          A "booster to the output tubes" is also commonly called an input driver, and it is a component of a tube POWER amp section - it is not a component of a tube preamp section.  These are two different things in an all-tube amp design.  Typical all-tube amps have "real" preamp tubes which shape the gain in the preamp stage, and they also have input drivers/booster and phase inverters in the power amp stage.

           

          I didn't say they have NO impact, just "very little" impact.  Changing the input drivers or phase inverters can affect the tone, but not as much compared to changing power tubes or preamp tubes (in an amp that actually has preamp tubes, which the SV does not).  I've done it in many amps, and the PI and ID have the least impact of all the other tubes - again, not saying that they have NO impact, but the impact is small compared to other changes.  I was responding to the guy who suggested keeping the power tubes and changing the 12AX7s.  My comment was that between these two sets of tubes, the power tubes will have more impact to the tone.

           

          L6 markets these tubes as "preamp" tubes on their literature, but assuming the FAQ is correct, the preamp section of the SV is all digital, and has no tube components, so changing the 12AX7s in the SV is not going to have the same impact that changing preamp tubes in an all-tube amp will.

           

          So, either the FAQ is wrong, and the SV does have a real preamp tube section, or someone else is spreading crap around, and its not me ;-)

          • mtrash14 Iknowathingortwo
            mtrash14
            539 posts since
            Feb 18, 2009
            Currently Being Moderated
            Mar 9, 2010 2:29 AM (in response to ResAlien)
            Re: Biasing your amp vs. the factory warranty

            Sorry if my replay sounded a little strong.     I edited that post and toned it down as much as I could (without completely deleting it)

             

            Again, I'm sorry if I sounded a bit edgy.

             

            Good luck

            M^T

            • ResAlien Just Startin'
              ResAlien
              86 posts since
              Jul 24, 2008
              Currently Being Moderated
              Mar 10, 2010 3:55 PM (in response to mtrash14)
              Re: Biasing your amp vs. the factory warranty

              Thanks bro, and sorry if I got a little cranked too.  BUT, I still disagree with you, assuming the information from Line 6 is correct.  V1 is a power tube input driver tube - it is not a preamp tube.  There are no tubes in the preamp section of the SV.  But, whatever, the amp really does sound awesome - and I've generally balked at the idea of using anything but an all-tube amp live.  The SV is def changing my opinion about that.

              • mtrash14 Iknowathingortwo
                mtrash14
                539 posts since
                Feb 18, 2009
                Currently Being Moderated
                Mar 10, 2010 5:40 PM (in response to ResAlien)
                Re: Biasing your amp vs. the factory warranty

                Res, I am very sorry I acted like a jerk.

                 

                Why did I get so cranked up?  Because I feel so deeply for the SV I think.  (that is as strange to say as it is to read I think)

                 

                Here is something I just said in another thread (copy/paste).  I think you you can see my true feelings in these words.

                 

                -----------------

                 

                This is only IMO.....

                I believe the SV was designed from the ground up to be a digital modeling amp.  If this were true then you wouldn't want a tube section in it that colored or changed the tone of the digital modeling section so the tube section had to be setup as such.  The SV has a preamp 12ax7 tube and the circuitry of it is just as any other tube amp but its a little different.  Its not supposed to have tube gain distortion as the volume is increased.

                The SV has lots of clean headroom as I believe it was supposed to have as designed.  The V1 12ax7 preamp tube does the same thing any other preamp tube in any other tube amp does and that is amplify the signal passing through it, but it does not color or flavor nor distort that signal as it does so.  With that being the case then if you were to say "it does't have a tube pre-amp" then in a way that is a correct statement, but at the same time that is also not correct, because it does indeed have a 12ax7 V1 preamp tube and that tube is doing what its supposed to do,  ie: amplify the signal going into the PI and the rest of the tube section, but you won't hear its voice, only the digital voice of the DSP, as its supposed to be.

                The true preamp in the SV is the digital modeling section, which is called the DSP.  *(digital signal processor)*.

                Again, this is only my .02$ and also only IMO.

                 

                --------

                 

                Peace man

                Later

                M^T

                • ResAlien Just Startin'
                  ResAlien
                  86 posts since
                  Jul 24, 2008
                  Currently Being Moderated
                  Mar 10, 2010 8:46 PM (in response to mtrash14)
                  Re: Biasing your amp vs. the factory warranty

                  Hey man - I appreciate your passion, and maybe we're in a semantics war - But one statement in that post is not quite accurate (though I agree your overall point is - Sorry, I'm an engineer by trade and get hung up on accuracy of minute details...it's a curse)  - the 12AX7 in V1 of the SV does not do what the "preamp tubes" in any other amp do - it does what the input driver tube in any other amp does.  I'm sure you know this, but the preamp section of a typical tube amp has two 12AX7s. The power amp section of a typical tube amp also has two 12AX7s and 2 or 4 power tubes.  These two 12AX7s in the power amp section are the input driver and phase inverter, and are not doing the same thing that the 12AX7s in the preamp section are doing.  Sure, the input driver is boosting the signal coming from the preamp section before it hits the power tubes, so I guess you could say it is "pre-amplifying" the signal from the preamp before it goes to the power tubes - but it is a little confusing to call this a "preamp tube", because this tube is physically not part of the preamp circuit.  (Line 6 is guilty of adding to this confusion because they call them "preamp tubes" on the box, but the FAQ clearly states V1 is an input driver, which is not part of the preamp circuit, so I don't consider them "preamp tubes" in that sense.)

                   

                  AFAIK, the preamp sections of the Spider Valve and Spider IV are exactly the same - the only difference is the power amp section - S4 has a solid state power amp and SV has a tube one, and all of the tubes in the SV are part of that power section.

                   

                  But hey, I guess we're way OT at this point, and I don't want to come off as a jerk either. The bottom line is that I agree that changing input drivers can affect the tone of the amp - just not as much as changing preamp tubes would, if the SV had any. 

  • Nick_Mattocks Expert Line 6 User
    Nick_Mattocks
    8,791 posts since
    Mar 26, 2007
    Currently Being Moderated
    Mar 7, 2010 5:11 AM (in response to stevementzer)
    Re: Biasing your amp vs. the factory warranty

    Hi

     

    This is what it says in the FAQ for Tube Troubleshooting and Replacement on this site for this amp:

     

    Q: Is Biasing covered under warranty?

    A: Typically not.  It should be considered as part of the routine maintenance in keeping your amplifier at its peak performance.   However, if re-biasing is required as part of other warranty service, it will be covered under the warranty policy

     

    To me that reads as if biasing the amp is part of standard routine maintenance and it won't invalidate your warranty.

     

    Nick

  • Line6Perry Line 6 Support
    Line6Perry
    6,652 posts since
    Dec 26, 2007
    Currently Being Moderated
    Mar 11, 2010 10:40 AM (in response to stevementzer)
    RE: Biasing your amp vs. the factory warranty

          Hello,

       

      Here's a similar (slightly different) thread to your question: http://line6.com/community/message/119342

       

      Basically the spec for biasing power tubes on your Spider Valve amp is: 35 mV +/- 2mV (standard bias trim pot adjustment method). If you feel confident enough in doing the work yourself, feel free to do so at your own responsibility/risk.

       

      Beyond this, we cannot provide you with schematics or servicing documentation as those are only given to our Authorized Service Center technicians in the field.

       

      If you cause damage to the amplifier during a self-attempted power tube change/bias procedure, any subsequent servicing to correct said potential damage is obviously not going to be covered under warranty. Any internal modifications to the amplifier's stock design voids the warranty, of course.

       

      Our new product warranty is 1 year from the date of new product purchase from an authorized retailer; honored at Authorized Service Centers around the country: http://line6.com/support/serviceCenters/

       

      Honestly, if you're experienced in doing such basic tube amp maintenance work, you should be fine. Our concern would be targeted more towards a novice who has never serviced a tube amplifier and is not aware of the potential dangers involved with stored charges present in components on the board.

       

      6L6 or 5881 tubes. 35 mV +/- 2 mV spec. Best in your creative endeavors.

       

      Regards,

      L6Perry

    • pixel2020 Just Startin'
      pixel2020
      19 posts since
      Jul 3, 2009
      Currently Being Moderated
      Mar 12, 2010 7:19 AM (in response to Line6Perry)
      Re: RE: Biasing your amp vs. the factory warranty

      Not to be a **** but just pick up the phone and call line 6 support if the posted information does not answer your question. All the line 6 documentation and or common sense will tell you changing the tubes will not void your warranty. Changing your car tires will not void the warranty so changing your tubes will not void the warranty.

      • stevementzer Just Startin'
        stevementzer
        38 posts since
        Apr 1, 2007
        Currently Being Moderated
        Mar 12, 2010 8:57 AM (in response to pixel2020)
        Re: RE: Biasing your amp vs. the factory warranty
        Not to be a **** but just pick up the phone and call line 6 support if the posted information does not answer your question. All the line 6 documentation and or common sense will tell you changing the tubes will not void your warranty. Changing your car tires will not void the warranty so changing your tubes will not void the warranty.


        Some manufacturers put factory seal tape on construction elements ....   Broken Seal = Broken Warranty.

         

        As for common sense.... the line6 documentation doesn't deal with this issue in particular. it basically states that you get a 90 day warranty on tubes and that an authorized repair center can replace them for you. it also says that the amp needs to be re-bias'ed after tubes are replaced.

         

        Your analogy regarding car manufacturers is flawed. If I discovered that a fuel injector needed to be replaced in my car, and after installing it, I programmed ECM to adjust the fuel flow rates .... the manufacturer could decide to void my warranty because I am not 'authorized' to make such repairs.

         

        As for picking up the phone, I am not particularly thrilled at the prospect of talking to a 1st-level tech support rep who spends all day answering questions like 'Why cant I use my podXT live in Windows 7 64 bit" or "Why wont monkey install?"

         

        My guess is that the tech support rep would tell me to take the amp to a service center to have the tubes replaced....

         

        Now the line6 rep answer is clear, and is now part of the internet, wayback machine and everyone can benefit from the answer.

         

        And yes.... you were being a ****.  

        • mtrash14 Iknowathingortwo
          mtrash14
          539 posts since
          Feb 18, 2009
          Currently Being Moderated
          Mar 12, 2010 3:19 PM (in response to stevementzer)
          Re: RE: Biasing your amp vs. the factory warranty

          +1

           

          Even though it appers L6 has said to go ahead and change tubes - I still stand by my first response.


          "The warranty is pretty important on these amps because of the digital processor inside of them and I suggest you don't do anything that might jeopardize that warranty."

           

          I said that based on my experience and I hope all of you will understand why I make my stand here.

           

          Good luck

          M^T

           

           


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