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325 Views 11 Replies Latest reply: Oct 15, 2012 8:49 AM by nitrous12 RSS
nitrous12 Just Startin'
nitrous12
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Jun 11, 2012
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Jun 14, 2012 11:24 AM

NAD - DT50 1x12 Combo

My HD500 actually just came yesterday too.

 

Had a little time to explore the DT on its own today and it has some good useable tones in it for sure. It can get pretty loud and on the Topology IV its pretty tight on high gain/volume for a 1x12. Should hold up jammin with a drummer, which was one thing I was worried about. Been a long time since I had a 1x12 and it fell apart at band volume on the high gain side.

I like the cleans I was getting from Top I as well. Top II and III are ok, but not really my thing. I like a little more gain than what their sweet spot is.

 

Only thing buggin me right now is there is a fairly noticeable rattle I can hear whe on the cleaner settings. Can't tell exactly what its coming from.

Anyone else hear that in their combo?

  • spaceatl Expert Line 6 User
    spaceatl
    4,456 posts since
    Jan 24, 2007
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    Jun 14, 2012 12:29 PM (in response to nitrous12)
    Re: NAD - DT50 1x12 Combo

    Only on louder volume?

     

    Perhaps, pencil test your tubes....crank the master and gentlely tap each tube with a pencil...If you have a tube loose plates, you should hear it...That can sound almost list loose reverb springs, but that will be coming through the speaker itself...

     

    check that the back peices are tight...might be be worth snugging all the screws if the amp was shipped....Another good thing to do with a shipped amp is remove and reseat the tubes....

    • nitrous12 Just Startin'
      nitrous12
      31 posts since
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      Jun 17, 2012 10:37 AM (in response to spaceatl)
      Re: NAD - DT50 1x12 Combo

      Playing around with the amp a bit more today.  Had some other strange static noise that wouldn't go away with volume and was on every topology.  Pretty sure its coming from the PTs as I put a different pair in and wasn't hearing it.

       

      The rattle is still there.  It is coming from something in/on the chassis as I can tap it and hear it.  The very odd thing though is if I set channel and master volumes to absolute zero I still hear it coming through the speaker.

       

      I just got this thing.  Hate to have to send it back to Line6 through a licensed repair center, but its not like I can't like w/out it.  I'll have to look at the return policy from the place I got it.  I don't want to pay to ship it back thats for sure.

      • spaceatl Expert Line 6 User
        spaceatl
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        Jun 17, 2012 10:55 AM (in response to nitrous12)
        Re: NAD - DT50 1x12 Combo

        The amp is much like a Class A type...basically, a typical class A has no master volume...So the master volume really isn't a master volume in the conventional sense because the power amp changes on the fly...

         

        loose plates in 12AX7s can make noise in the speakers...My thought is that you need might need new tubes...

         

        The tubes have a 30 day warranty, so it might be worth giving Line 6 a call directly to see what you options might be on that...

  • nitrous12 Just Startin'
    nitrous12
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    Jul 26, 2012 6:13 AM (in response to nitrous12)
    Re: NAD - DT50 1x12 Combo

    Hi folks...been a bit since I posted about this.  I never had a chance to get the amp to a tech yet, but I have some of my own findings to report.

     

    The other day I was noticing a lot of strange hissing and background noise really creeping in again so I decided to try swapping some tubes.  The first 12AX7 I replaced stopped that noise for about 5 min, but it came back.  The other thing I realized right away was that the rattling noise was much worse.  With the only change being that preamp tube I reached around and grabbed it and when I physically hold the tube and stop those vibrations I don't hear that noise through the amp.

    I grabbed a 3rd preamp tube and it stopped the noise for the 20 min or so I was able to play and reduced the rattling noise to a large degree.  It is still there, but is really only heard on the clean tones. 

     

    So the rattling is from the tube...the one furthest from the transformer so whatever that position is.  Since it is a combo any chassis vibrations are going to go through the whole amp down to every component.  But I wouldn't think this is acceptable to hear this so I am wondering if the tube socket has a problem?  I don't know of a way to dampen the tube that wouldn't burn/melt.  It would be great to resolve this and have no audible trace of that vibration, but it is useable and a lot of fun to play with the HD500 connected. 

    I probably will still try to get it to the shop even if its just to have them give me a brand new pre with no noise and 'hopefully' no vibration.

    • spaceatl Expert Line 6 User
      spaceatl
      4,456 posts since
      Jan 24, 2007
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      Jul 26, 2012 8:02 AM (in response to nitrous12)
      Re: NAD - DT50 1x12 Combo

      That sounds like a loose plate is the tube....You have to replace the tube...I still have china 12AX7 that came in the SV MK2 that has a broken weld on the plate...In fact, it is so bad that with the tube in your hand you can thump it and both hear and feel the plate vibrating...When it was in the amp, it came the illusion of a rattle coming from the faceplate of the amp and the speaker....Probably one of the most unusal tube failures I have ever seen or heard...You should have 90 day warranty on the tubes...Anyhoo, it isn't an unusal problem, especially if the amplifier was shipped to you...

      • nitrous12 Just Startin'
        nitrous12
        31 posts since
        Jun 11, 2012
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        Jul 26, 2012 10:51 AM (in response to spaceatl)
        Re: NAD - DT50 1x12 Combo

        Yep, I don't disagree with you.  However, seeing that I tried 3 different preamp tubes and the all did it to varying degrees makes me a little suspicious.  Is there something else adding to it that makes this amp right now a bit more susceptible to picking up and amplifying even the slightest vibrations of the plates?

        I'll take her in sometime here.

        • spaceatl Expert Line 6 User
          spaceatl
          4,456 posts since
          Jan 24, 2007
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          Jul 26, 2012 11:53 AM (in response to nitrous12)
          Re: NAD - DT50 1x12 Combo

          Could be sockets...All tubes are microphonic and loose sockets can be an issue for any tube amp...It's the nature of the beast...The tubes are amplifying...

           

          I guess one way to start is remove all the tubes and gently tap the sockets and see if you hear springs rattling...sockets can be replaced...

           

          BTW - I use Mesa SPAX7s...They have heat shrink on the glass...very quiet tubes...

          • nitrous12 Just Startin'
            nitrous12
            31 posts since
            Jun 11, 2012
            Currently Being Moderated
            Jul 26, 2012 12:21 PM (in response to spaceatl)
            Re: NAD - DT50 1x12 Combo

            I have had those Mesa preamps in the past.  I thought of those when I was holding the tube and the noise was stopping and my brain went to 'what can I get to hold this thing so I can use my hand to play'

             

            I'll post back when I get further with this.

            • nitrous12 Just Startin'
              nitrous12
              31 posts since
              Jun 11, 2012
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              Oct 15, 2012 8:49 AM (in response to nitrous12)
              Re: NAD - DT50 1x12 Combo

              UPDATE:

               

              I tried posting my update like 2 weeks ago, but the fourm didn't seem to be working right.

               

              Anyway, I took my DT50 into the local service center.  All they did was replace one or both of the 12AX7s.  The rattling sound is definitely much better.  If I try hard enough I can find it a little bit by hitting the right note on a clean setting, but for all practical purposes its not an issue any more.

               

              The first time I played it at home after picking it up, about 15 minutes in I started hearing the same crackling vacuum like sound.  Needless to say I was quite annoyed.  Since then though it has been pretty good with only a few random times that I have heard it.  I would say the last 4 times I fired it up I didn't hear it at all.

               

              However, I have been getting something else randomly now and its a down right scarey noise that I have never experienced before.  The first time it happened was maybe the 2nd or 3rd time firing it up post servicing.  When I did the first topology switch this insane screaming noise came out...loud!  Louder than the volume I was playing at and not like any feedback I have ever heard.  Adjusting any switch or volume did nothing...I had to turn it off.  It repeated this propbably two more times until I turned it off and walked away.  The next time I fired it up, let it warm a bit and it was fine.  It has done this here and there probably 4 or 5 times now.

              Last night I plugged in and went to play and had no sound.  Went to adjust the volume knob and it did it again.  Repeated twice.  Shut it down for a few, turned back on and let it warm before going off Stby and then it was fine.

              Weird intermittent stuff with this thing for sure.  Glad I am not gigging with it.  The real pain though is that it is so random I don't know that I could get it to do it at a service center to try to find the issue.  I hate that!

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