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Using Tube Amps with other inputs

Discussion in 'Amps and Cabs [BG]' started by unatratnag, Nov 8, 2005.


  1. Question is why do alternate forms of inputs besides the instrument damage the tubes on tube amps? I assume this applies to bass amps as well, but this question is derived from our guitarist saying he didn't know why, but he knew you can't put vocals through his marshall jcm 2000 tube amp.

    What's causing the damage to these tubes?

    Second, what about loop pedals and such. Some of those come with factory presets with bass and drums etc on them. Would those damage the tubes as well? I would assume if they did they'd put a warning on the manual but my jamman doens't say anything of that sort (from what i see).
     
  2. It doesn't.
     
  3. Passinwind

    Passinwind I Know Nothing Supporting Member

    Your guitarist is misinformed. An unbalanced high impedance mike will work fine into his amp in terms of electronics, although it may sound pretty bad. A standard low impedance balanced mike will need an inline transformer, which you can readily obtain at Radio Shack or many other places. The second case will sound very bad in many cases without the transformer, and could lead one to believe they've damaged something.

    Second, what about loop pedals and such. Some of those come with factory presets with bass and drums etc on them. Would those damage the tubes as well? I would assume if they did they'd put a warning on the manual but my jamman doesn't say anything of that sort (from what i see).


    As long as you don't overload the amp's input or create uncontrollable feedback, you're golden, basically.
     
  4. hmm... well this happened 4 years ago...but at one point while me and the guitarist were away our singer used a sure sm58 mic thru the amp and the tubes were definately damaged.

    So you're going to guess this was just a freak coincidence then huh? and that it was just the time for the tubes to go to tube heaven and had nothing to do with the mic?
     
  5. Impedance
    Rated impedance is 150  (300  actual)for connection to
    microphone inputs rated low impedance

    does this mean it's low imp? In which case since there was no transformer to increase resistence/reactence etc, wouldn't that be bad?
     
  6. Passinwind

    Passinwind I Know Nothing Supporting Member

    If I had to guess, it'd be that your singer kooked out, didn't use the transformer that I mentioned (yeah, that 58 is low impedance), turned the amp way up to compensate for the thin sound, and probably pulled one or two more bogus moves at the same time. In other words, it wasn't the mike's fault, it was the operator's. :cool:

    I've been repairing tube amps for over 30 years. Believe it or not, you can plug a microphone into a tube guitar or bass head and it'll survive in the vast majority of cases. ;)
     
  7. stupid mike.......... (singers name is mike :smug: )

    makes perfect sense, thanks!
     
  8. thedoctor

    thedoctor

    Jun 20, 2005
    There are just two sets of rules with people using your stuff:
    #1 Don't
    #2 Don't

    Never loan chainsaws, MIG welders, plasma cutters or amplifiers to ANYONE, your mother included. The Shure mic was not in the least bit ready to drive the hi-Z input of your amp so the singer did all he knew to do. Crank the crap out of it with a very uninterested preamp section. You are correct in that the tubes getting replaced was not the worst thing that could have happened.