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Tube head hum?

Discussion in 'Amps and Cabs [BG]' started by superfly, Nov 23, 2004.


  1. superfly

    superfly

    Aug 4, 2004
    I was checking out an Ampeg V-4BH all tube head today. 100 watts all tube. I noticed alittle "hum" when I turned the standby off and engaged the tubes. Is alittle hum normal from tube heads, or are they supposed to be silent?
    The hum was ever so slight, almost like normal operating noise, but only when the tubes were "on". Not in standby mode.
    This one was 2 yrs old , looked brand new and had groove tubes. Are GT's stock from Ampeg?
     
  2. Nick man

    Nick man

    Apr 7, 2002
    Tampa Bay
    It was probably the bass.
     
  3. superfly

    superfly

    Aug 4, 2004
    Without anything plugged in. Tube heads aren't totally silent are they?
     
  4. Yes they can be completely quiet. My 30+ year old Ampeg V4has no hum whatsoever.

    I do not know if the new Ampegs hae this adjustment, but mine has an adjustment pot on the back that neutralizes the hum through the filaments.
     
  5. An improperly biased amp will also have a hum.
     
  6. Arthur U. Poon

    Arthur U. Poon

    Jan 30, 2004
    SLC, Utah -USA-
    Endorsing Artist: Mike Lull Custom Basses
    Both the SVT-CL and SVT-2 Pro I owned did the same thing as your V4BH. Regardless whether I had been using the amp for hours and hit the standby switch for a break, and then flipped the standby switch off and went back to playing.

    Or at initial power-up after the tubes had warmed up for a minute or two. Either scenario it would make the noise you're describing. Not everytime, but it would do this frequently. I have no idea why.

    Hopefully Psycho Bass Guy will read this thread, he'll know if it's any cause for concern or not.

    -Art
     
  7. Arthur U. Poon

    Arthur U. Poon

    Jan 30, 2004
    SLC, Utah -USA-
    Endorsing Artist: Mike Lull Custom Basses
    Psycho Bass Guy posted in the time it took me to type my post! Plus, I went and got a cup of joe.

    I don't type very well. :D

    PSB, My old SLM/SVT's did this when the amp was 'biased' as per the owner's manual. Both bias LED's would be glowing green and only once I started playing would the red LED's come on. Perhaps my bias LED's weren't accurate, but while the amp was running (standby off) they were relatively hum free. As a matter of fact, while turning the bias LED's slightly a humming sound would be present when the red LED's would light up.

    Any ideas?
    Thanks, Art
     
  8. Arthur U. Poon

    Arthur U. Poon

    Jan 30, 2004
    SLC, Utah -USA-
    Endorsing Artist: Mike Lull Custom Basses
    PSB: BTW, the hum is a short thumping sound with a hum when the standby is turned off, and it lasts for less than a second.

    Hope that helps.
    -Art
     
  9. superfly

    superfly

    Aug 4, 2004
    I stand corrected. There is no hum until a speaker is plugged in the back. And then the hum is through the speaker.
    Sorry! Its just the speaker I guess ?
     
  10. Arthur U. Poon

    Arthur U. Poon

    Jan 30, 2004
    SLC, Utah -USA-
    Endorsing Artist: Mike Lull Custom Basses
    I'm no expert, but I believe with tube amps you should always have a speaker load connected when you power up the amp.

    Is the hum a short thump/hum like I described above, or is the hum continuous? If it always hums, without your bass plugged in, look at the Bias LEDs on the back panel of your head. You should only have green LED's glowing. If the red (or red and green) LED's are lit up, slowly turn the pots under the LED's until you only have green LED's showing.

    -Art
     
  11. Tube amps are totally quiet when nothing is plugged in because the jack shorts the signal to ground.

    Tube amps will have slight hum in operating mode.
     
  12. It's not the speaker. Speakers don't just hum. If there is a hum, it's coming from the amp feeding it.


    That ONLY occurs in older Fender amps. Most modern amps don't. You should NEVER NEVER NEVER NEVER EVER attempt to run a tube amp (or ANY kind of amp which uses an output transformer for that matter) without the properly rated speaker load.
    No they won't.

    BTW, I don't take much stock in SLM's "bias" LEDs because they only account for a static "average" voltage rating and depending on the variation among different tube makes, can still show "RED" and the amp be properly biased.
     
  13. couldn´t be more clearer than that.
    :)
     
  14. superfly

    superfly

    Aug 4, 2004
    Problem solved! Thanks to forum member JonB for his advice.

    It turns out I had 2 blown fuses that protect the tubes. So I was only running at 50% tube power. I changed all the preamp and power tubes, rebiased , replaced the 2 blown fuses and kaboom! This sucker is almost dead quiet now while idleing, and has more than enough power now.
    If anyone else here has a V-4BH and they don't think its loud enough, than check all of the above items I mentioned. Can you say "baby SVT"?
     
  15. way to go!