Amp hums, then doesn't.

Discussion in 'Amps and Cabs [BG]' started by Michael Jewels, Oct 10, 2001.

  1. I have a Fender Bassman 60, but lately it seems to hum sometimes. The two basses I run through it mostly are my Jack Casady and my Yamaha BBN5II.
    Both of these basses are quiet, especially the Yamaha. When it hums, you can notice it as soon as you turn it on, so; could it be the electricity in the house? This amp and either of these basses have never given me problems before. The odd thing about it is that it only happens on some days. As far as I know nobody is running any kind of heavy appliance nearby. Also, this just started happening lately. Any ideas?

    Thanks, Mike J.
  2. Chasarms

    Chasarms Casual Observer

    May 24, 2001
    Bettendorf, IA USA
    Sounds like the old 60 cycle hum.

    Is the furnace on when it hums? Since it is just now getting cold, I'd guess furnace. But any appliance can sometimes cause this.

    Can you lift the ground on that amp? Try that. If there is no ground lift switch, pick up one of those cheap little things at the hardware store that allows a grounded plug to be plugged into a non-grounded outlet.

    If this doesn't work, I guess it could be something in your amp, but that is unlikely.
  3. Maybe it is 60 cycle hum, maybe not.

    But do not defeat the ground on your amp. It is there for a reason and it is dangerous to defeat it.

    60 cycle hum is usually caused by a ground loop or insufficient grounding. If you have something else plugged in to AC that is connected to your amp, such as an effects unit or if you are going out to an external amp, start by disconnecting that to isolate the problem. Try different guitar cables.

    If you can't seem to isolate the problem, it may be the amp.
  4. Freakapotamus9


    Jun 20, 2001
    could it be the instrument cable????
  6. MikeyD


    Sep 9, 2000
    Maybe it forgot the words. ;) Seriously, though - it should have a good ground connection on a correctly-wired power circuit. That's the first thing to check. You can get a circuit checker at a hardware store. It will show whether it is properly grounded. I recommend NOT using a 3-to-2 wire adapter, especially if there is 3-wire power available.
    - Mike
  7. Captain Awesome

    Captain Awesome

    Apr 2, 2001
    Why is it called 60 cycle hum? Does it occur at 60 Hz?
  8. Mike N

    Mike N Missing the old TB

    Jan 28, 2001
    New York
    The frequency of the current coming through the wall outlet is 60 Hz.
  9. Last night everything was cool. No hum or anything. I didn't get rid of the 3-2 adapter, but will shortly. I think I can find a dedicated outlet for Mr. Bassman, he deserves it. Maybe it was the furnace. Thanks everyone.

    Good Weekend,
    Mike J.
  10. Gosh dangit! I moved the amp's plug to a grounded
    three prong outlet, and thought that did it. It's still the same, sometimes it hums; sometimes it doesn't.
    The other day I turned it on, no humming, and I had it on for 5 hours. I shut it off for about 2 hours then turned it back on, and it was humming again. Also, now it sometimes makes a flopping sound like the speaker is blown, but not all the time. Could the amp just be starting to go? Has anyone ever heard of an amp bahaving like this? It' not even a year and a half old. What do you guys think?

    Mike J.
  11. It could be an amp problem.

    When it is humming, does the hum respond to the volume control?

    When it is humming, if you disconnect the guitar cable so that nothing is plugged into the amp, does it continue to hum?
  12. Martin, yes. it does respond to the volume control. The louder I turn up the amp, the louder the hum gets. I haven't tried unplugging the cable, I 'll do that tonight. The thing that gets me is that the humming is either there when you first turn it on, or it's not. It never starts to hum after it's turned on. If there's something wrong with it, shouldn't it hum all the time? Unless there's something in the output stage that's starting to go. I can't figure this thing out, although I have started to think about getting another amp. Ugh!

    Mike J.:(
  13. If it were in the output stage, it would not respond to the volume control. Try unplugging everything from it when it's humming and see if goes away. This will help isolate the problem.
  14. I'd like to isolate the amp on a dessert island. I also have my 24 year old Yamaha amp that's just siting around. I'll try that tonight. Could it be something in the line that's coming from a source nearby?

    Mike J.
  15. It could be. You don't happen to have florescent lights nearby or a light dimmer. These would be prime suspects as an external source.
  16. Seriously, and all kidding about G.A.S. aside, I think my amp has had it. Here's the latest:
    1) I unplugged everything, then the hum stops.
    2) I tried different cables, the hum doesn't go away.
    3) I plugged it into another dedicated outlet, no change.
    4) It now always has that fuzzy, floppy blown speaker type sound on all notes lower than open D.
    5) Check out this new and exciting development; now the midrange control has no affect on the tone. Interesting, huh?

    I love the sound of this amp, but, in the last two weeks it has undeniably changed. I don't know what happened to it, but, it is messed up. Maybe it was half a lemon from the beginning and now it's just falling apart, who knows? These are pretty weird symptoms though, wouldn't you say?
    Thanks to everyone for your help, but, I think I just have to buy another amp.

    Mike J.
  17. chhogg


    Oct 19, 2001
    Amazing! I am having almost the exact same problem! I have a Crate BFX-50 amplifier, and it has recently been causing lots of problems for me. I wouldn't describe the sound as a hum at all, but sometimes when I play there will be a buzzing / overdrive-ish sound even at very low volume levels. This occurs with three different basses. My problem is also similar in that if I turn the amp on and don't have a problem, then I can play for hours but if I turn it on and there is a problem, then sometimes leaving it on for an hour will help but other times not. It seems to me that this problem only occurs in my dorm room. However, this may not be the case. Most of my playing is in my room and since the problem is intermittent, it may be that I have just been lucky playing in other locations. Oh, and the problem that I have is frequency dependant. It is usually worst around the 3rd fret on the E string and the 12th - 16th frets on every string, but sometimes it occurs on nearly every note. I have no idea what to do about it, but buying a new amp is definitely not an option for me.
  18. chhogg,

    What you are describing sounds more like a cabinet buzz. Sometimes these seem to be electronic but are really just some loose screws perhaps. If I understand you correctly, your amp buzzes only when playing. Mike's hum is there regardless.
  19. Hey chhog, welcome to Talkbass. Wow, that's weird that you're having almost the same problem but, with a different brand of amp. There's a bunch of very knowledgeable people here, and no one could figure this out. I think I just might have gotten a lemon, and that it didn't really fall apart until now. I didn't really want to buy another amp, but, my Bassman is now just about unplayable. This never happened to me before, but, I have heard of other people having trouble with certain makes/models of amps. I hope you can straighten out your problem. Welcome aboard.

    Mike J.
  20. Michael,

    The more I think about your scenario, the more I think it may, if fact, be a problem with the amp (somewhere in the preamp stage). This is not to say that the amp is falling apart. Electronic components do fail. Most of the time, to part itself is only 1 or 2 dollars, but the labor charge to replace the part sometimes exceeds the value you place on the amp. Kinda like a car, if you could fix it yourself...