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Static/noise on a Channel?

Discussion in 'Pro Audio Equipment' started by DamonY, Jun 18, 2006.

  1. DamonY

    DamonY Guest

    I've got a lovely sounding vmp-4000e pre, but have lately discovered a low volume intermittent static coming from channel 2 and some hum in channel 3. Channels 1 & 4 sound clear. I have only just put in an email to Seb, but wondering if anyone else has encountered this in a preamp and what it could indicate? I have checked the cables and grounding, and it definitely seems to be coming from inside the unit, as I also hear this when nothing is plugged in. Its driving me nuts as we are about to begin a big session this week and I need to be able to use all 4 of these babies.

    Thanks,
    Damon
     
  2. RemyRAD

    RemyRAD Well-Known Member

    They just don't make tubes like they used to. Welcome to the land of thermionic devices and imperfect capacitors.

    If you are hearing these sounds with no input loading, that is, nothing plugged into the microphone input, you WILL generally hear more noise with an unterminated input.

    Have you tried opening the box and rearranging the tubes? See if the problems migrate with the tubes? Also make sure that you let the box warmup for at least 2 hours or more.

    On some preamplifier's the tubes have external spring-loaded metal can like envelopes, that slip over the glass envelope so as to keep spurious electromagnetic interference i.e. hum from being picked up by the tube. Sometimes you can tap on those and the noise may disappear?

    But that low-volume intermittent static could indicate just a crappy tube or maybe a faulty power supply decoupling capacitor?

    This is what they make software noise reduction for.
    Ms. Remy Ann David
     
  3. DamonY

    DamonY Guest

    Thank you for the advice - I am new to the tube world. These sound like good ideas to try; I may hold out a litle longer and see what Seb says before I open the box. And actually, I don't usually give it that long of a warm up, so I'll try that today. -D

    :?
     
  4. DamonY

    DamonY Guest

    Static/noise on Channel persists

    I know it took a while, but I finally tried switching the tubes around and had no luck with the noise. It didn't clear up or migrate to the other channels. Could a bad power capaciter effect just one channel? Do you think there is a fault in the circuitry of this channel?

    Thank you for your help on this,
    Damon
     
  5. RemyRAD

    RemyRAD Well-Known Member

    I think you better contact the manufacturer? A bad power capacitor would cause problems throughout the unit. A bad capacitor in a single channel could cause the problem in that channel and there are many capacitors in each channel. In all probability, it's not a capacitor problem? Capacitors are usually quite reliable and although "electrolytic" capacitors age and fail, it usually takes some years. Whereas an integrated circuit chip I would be more suspect of. "Cold solder joints" from too little heat during the manufacturing process could also produce the problems you are having?

    I would however make sure all cables are in good condition. All too often these problems can arise from substandard or worn cables. One of the popular brands at many of the music stores are "HOSA" cables and I have had problems with relatively new ones so just because they might be new does not mean they are good. I think they should be called "HOSEBAG"??

    It's operator error 80% of the time
    Ms. Remy Ann David
     
  6. Sebatron

    Sebatron Well-Known Member

    Good call Remy Rad. :cool:

    Damon sent me this email only a few days ago:

    “ OK, I re-did the connections and nothing changed. HOWEVER
    I moved the tubes again and wa-la, Now I DO notice that the intermittent static DID migrate with the tube movement!
    Apparently one of the tubes has static at low volumes in whatever channel it lives in.
    (I don't have a clue why this didn't seem to happen last time.. maybe I dumbly reshuffled the tubes twice.) “

    Hooked on Stravinsky? :!:

    8)
     
  7. RemyRAD

    RemyRAD Well-Known Member

    Thanx Seb! 8)
     
  8. pmolsonmus

    pmolsonmus Well-Known Member

    Hi,

    A similar problem popped up in mine and I'm guessing its a tube. In doing a little search here it looks like JJ is the direction others are going, but I couldn't find the model number.
    I suppose it will be obvious when I take the hood off, but I'd like to have the replacement part in hand when I go to do the job. Any help out there?

    Your recommendations or Sebs?

    Phil

    BTW I love this unit. I've been putting off a self-produced recording because I have been unhappy with the sound of my voice as I could record it. (that's kind of big deal as a singer and vocal coach) I know its not normal but I use My K2 with the Seb and I'm lovin' it. The Cd should be done by December.
     
  9. Alécio Costa - Brazil

    Alécio Costa - Brazil Well-Known Member

    2 hours before using the unit?LOL

    I have been using my box since Nov.2003 and all I have done is turn the unit for a few minutes before tracking.

    These noises are probably due to Tube aging/overuse.

    My VMP2000VU started presenting these noises. Just substitued the tubes.
     

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