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Discussion in 'Amps and Cabs [BG]' started by marcinkus, Dec 27, 2001.

  1. Two hours ago I was switching my Ampeg V4b tube head on but I didn't notice there was no speaker connection. :mad:
    I immediately turned it off, plugged the speaker and switched the amp on again. Everything seemed ok.
    I hope I didn't fry anything... should I bring it to any qualified service center? :confused:
  2. Do you mean that the speaker cable was plugged into the head but not to the speaker?

    That should be fine as long as the cable doesn't touch anything that might short the connection.

    It is also fine to not have any cable plugged into the head at all.

    Did someone tell you that this was a problem?

    - Dave
  3. With the standby switch on or off?

    It'll be fine...the damage really occurs when the standby is ON and you're actually making the amp work. Virtually every tube amp will survive even long periods turned on, standby OFF, with no speaker.

    The only time you'd need to get a tech involved is when the sound changes after you plug the speaker in...generally it's the output transformer that will blow though.
  4. Well, the speaker cable was plugged into the head but not to the speaker and I switched the standby ON... :(
  5. As long as the tip of the speaker cable did not come into contact with anything conductive, you should be perfectly fine. I don't know of any way you could damage an amp by having the output at infinite impedence ( i.e. an open circuit ). It's low impedence that causes problems. If anyone knows otherwise, please clarify.

    - Dave
  6. Wxp4759cb


    Nov 23, 2000
    Kansas City, MO
    Not really related but....

    I really like your avatar Dave. Did you make that yourself?
  7. Yep ...



    Check out http://www.jsbach.net/bass/ for some more info about that ...

    - Dave
  8. ...And this is what kills the output transformer - not seeing any load on the other end. Low impedence, yes, is another killer.

    Your amp will be fine. As said earlier, only worry if it sounds different or doesn't fire up! :) I've done the same thing on pretty much all my vintage amps at some stage, and have never fried anything.
  9. Solid State amps only Dave, i'm afraid...
  10. Oops, clarification:

    Solid State POWER amp sections only (ie all solid state or tube preamp, SS poweramp). You cannot run an all-tube amp (such as a V4B) with no speaker.
  11. I guess I'll have to retract my statements about running with no load. This Tube Amp FAQ concurrs that it is bad to run with no speaker:


    It doesn't say why though. I figured that running with no speaker is like running with a speaker of infinite impedence. I have never heard of high-impedence being capable of damaging an amp.

    - Dave
  12. Ahhh, but with no speaker attached, the output transformer sees a zero load...ie zero impedence.

    Somebody like throbbinut, bgavin, Joris and the "real" techos would be able to give the "mathematical" explanation.

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