Normal for Tube heads/Pre/Power Amps to hum?

Discussion in 'Amps and Cabs [BG]' started by modulusbassist, Nov 7, 2001.

  1. Is it normal for tube anything head, pre amp, and power amp to hum? Is this the microphonic that the amp picks from the tube? Is there any tube driven head, pre and power amps that does not hum?

    I like tubes but I hate the hums.

    How's your tube driven gears? Lots of hum or silent?

  2. Tapp


    Aug 29, 2001
    USA, Mississippi
    Well, it's normal for an amp to make some noise a little transformer hum and speaker hiss is considered normal but this would not be audible enough to worry with. Sometimes tubes that are going south will hum, but many times a microphonic tube is indicative of a ring or feedback.

    Many times the hum is due to poor filtering in the power supply or bad grounds (or someone pulled the ground plug out). These are fixable with proper maintenance.

    What tube amps have you experienced that hummed?

  3. I dont have an all tube bass amp, but i do have an all tube guitar amp, and with the Reverb all the way to zero (design flaw by fender in the blues jr.) it is DEAD quiet, and the only sounds that come out is the sound of my playing (unless i'm using single coil pu's, but thats 60-cycle hum). My Eden Halfstack which is a hybrid makes the standard "static" noise due to the 800w poweramp. I have no microphonic feedback comming from either amp.
  4. Same as muttluk, I have Eden WT-800 and Epifani 4x 10.

    But something funny happened. I am waiting for my Furman Conditioner and until the thing is delivered, I took my home theater power conditioner made by Chang Lightspeed you are familiar with this brand) that filters and protects my 2000 watts 5 channels amplifiers and connect the Eden to the Chang.

    And I noticed that the notes coming out of my bass is clearer, the tones are fuller, tight and taut. My E string sounded tighter and punchier, and the noise floor is significantly reduced. Although it still hisses, it is much more quiet. So I am using the Chang as a temporary fix until my Furman arrives but I am scared that I won't be able to disconnect my Eden from the Chang.
  5. Paul A

    Paul A

    Dec 13, 1999
    Hertfordshire U.K!
    What Key is it doing it in?
  6. FalsehoodBass


    Jul 22, 2001
    Denver, CO
    if you have a premp/poweramp setup, i've found that you can minimize hum by turning the volume all the way up on the preamp, and then using the poweramp's controls to regulate you're volume... since the hum most likely comes from the preamp, by turning the volume all the way up on the pre, the hum will be amplified less when it gets to the poweramp... if that makes any sense
  7. Paul A

    Paul A

    Dec 13, 1999
    Hertfordshire U.K!
    Usually lots of hum is due to the heater supply to the valves (or one or more valves going faulty).
    It's not unusual to have a small amount of hum due to most domestic mains supplies not being too "clean" - a power conditioner certainly helps here.
    Lots of hiss is usually down to the power supply filter capacitors breaking down.
    If its an old amp (anything over 6 or 7 years old) you would notice quite a difference if you had them changed by a tech.