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need help from master electrician

Discussion in 'Amps and Cabs [BG]' started by fredsoffa, Mar 2, 2003.


  1. fredsoffa

    fredsoffa

    Mar 2, 2003
    Bought an Ampeg Bn-15. Sounded great at the owner's house. In my apartment amp has loud 60 cycle hum. Electric in my place is bad (refrigerator hums, and amp mimics it very closely).

    Amp has original 2 prong plug. Polarity switch has no discernible effect. Have tried outlets in other units, but perhaps problem is building wide.

    Previous and still current amp set-up (Lab Series L2 and Carvin 18") is clean.

    Suggestions welcome!

    fred
     
  2. If it was good sounding in another building, then I'd suspect the power in your building to be the problem. Try taking it to yet another location to try it out.

    I still use a few old tube amps with 2-prong plugs, and they are as quiet as can be. The 3rd prong is for safety, not noise reduction, so you should be able to have a quiet amp with the original 2-prong plug.

    Chris
     
  3. fredsoffa

    fredsoffa

    Mar 2, 2003
    My firiend Dennis has suggested that I get a surge protector, pop it open, then take that ground to a solid metal object inside the apartment. His strategy here is to break the loop inside the apartment. How does this sound?

    Unfortunately for me, I know the power in my apartment is bad, and I am not yet in a position to move for the amp. yet.

    fred
     
  4. One more suggestion. Go get an outlet tester at a hardware store. It will show you if you have a phase problem, or other such issues. Other question. Does the amp make noise without a cable plugged into the input jack?
     
  5. fredsoffa

    fredsoffa

    Mar 2, 2003
    Yes, amp makes noise when just plugged in. And so did a Fender SPA 100 rack mounted amp I used in lieu of a regular stereo amp. And, so does my refrigerator. I can hear the cycle in the frequency change of the compressor noise.

    The devices seem immune:
    my mackie mixer, thank god, my computer
    NAD 3140 amp

    and like I said, the first amp rig

    The Ampeg does make even more noise with the cable plugged in. Less if I touch the metal housing of the cable jack (clearly I am the ground there)

    fred
     
  6. Mickey Shane

    Mickey Shane what goes here?

    Feb 23, 2003
    Denton, Texas
    You have dirty AC in your apartment. The 2-pronger would work fine with cleaner AC. A 3 ft. spike in the ground outside, a cold water pipe, or (if you have it) the third hole in your wall outlet will help (if it's connected). Take an insulated piece of braided wire and connect it to a chassis screw on your amp, then connect it to one of the three above mentioned items.

    Or, buy a Furman line conditioner ($49) and plug your amp into that.
     
  7. fredsoffa

    fredsoffa

    Mar 2, 2003
    say, other people have dismissed line conditioners as being of value in this situation. Have you used the line conditioners to defeat this problem?

    I am planning tomorrow to make an assault on some copper piping in my building, and will used braided wire as you suggested.

    fred
     
  8. You're bathing in electromagnetic fields. I don't think any of the crazy grounding setups mentioned above is going to help you. They may even make it worse.

    I think you may be screwed.

    Do get an outlet tester just to make sure the hot and neutral aren't reversed.

    And drag your amp, cable, and bass over to somebody else's house to confirm it is indeed your apartment.

    I suspect it's not so much the actual dirty power on your wires, as it is the fact that you are surrounded in all directions by the wire (and current) flowing in other peoples refrigerators, etc.

    Chris
     
  9. PhatBasstard

    PhatBasstard Spector Dissector Supporting Member

    Feb 3, 2002
    Las Vegas, NV.
    Some of the more expensive (starting around $30) power strip/surge protectors also have AC filtering to help eliminate the problem you're having.

    The black metal ones I get at Radio Shack for $30 work for me for this problem when I encounter it.
     
  10. fredsoffa

    fredsoffa

    Mar 2, 2003
    I have two Tripplite surge/filters, which I consider to be the best available.

    However they have not solved the problem in the past.

    fjs
     
  11. PhatBasstard

    PhatBasstard Spector Dissector Supporting Member

    Feb 3, 2002
    Las Vegas, NV.
    In that case I have to go with the person that said you're probably getting interference from something else (i.e. lighting, tv, home stereo, etc.,etc.). Especially since its happening only in your apartment.

    Have any other amps you've had in your apartment had this problem? Are you using the same bass? Same cord (possibly/accidentally using a unshielded/speaker cable)?

    I know some of this sounds very obvious but I'm trying to think of all the things that could cause this problem (sometimes the most obvious things get overlooked).
     
  12. fredsoffa

    fredsoffa

    Mar 2, 2003
    Sorry about the delay in the reply.

    I finally have had time to assault the problem. Wired chassis (temporarily as of yet) to grounding screw inside surge protector AND rotated very handy and somewhat effective "HUM BALANCE" screw on back of amp.

    These two operations has reduced problem 90% on the db scale, to the point where I can at least now practice on the amp.

    So thanks for all the timely help. Was really impressed by the number and quality of responses. I am sure I will have more questions later!

    Also, I am going to take amp to other side of building and see if it is clean there. Just to get info on another variable.

    thanks again. Fred
     
  13. Hum balance is an inverter phase control. Adjusting it usually compensates for mismatched tubes. Which action took out the most hum? If it was the hum balance adjustment, you should hae been having hum problems elsewhere. You have to be VERY careful messing with hum balance or you can quickly burn out a set of output tubes and the output transformer.
     
  14. fredsoffa

    fredsoffa

    Mar 2, 2003
    Hard to say which one had more effect. Will have to break it back down and do the set up again.
    Thanks.
     
  15. PBG,

    I think on the B-15 the hum balance is just a pot across the 6.3V winding, so it's not adjusting the bias of the tubes like in a Fender.

    Chris
     
  16. Wes Whitmore

    Wes Whitmore Supporting Member

    Mar 10, 2003
    Columbus, OH
    I suggest borrowing a UPS backup and take it home. First see if the filters built into the UPS solve your issues. If you still have noise in your system, pull the plug and run the amp off of the battery for a little while. If the noise stops, then you have a power issue for sure (sounds like you do anyhow, but its a good test). It gives you some ideas to go with, anyhow.
    You could always run a dedicated 3-12 cable directly to the breaker box and run it off of a dedicated breaker. That might help as well.

    Wes
     
  17. fredsoffa

    fredsoffa

    Mar 2, 2003
    Thanks again for the all input.

    I would like to believe that the hum-balance on the ampeg is benign, since it is user accessible. I just tweaked it a bit, and now amp is pretty quiet. Not dead quiet, but pretty.

    I know the problem is in my box, and beyond, because the power from my next door neighbors - when I plug in - is just as bad. Also, have a GFC in the bathroom. That is of no value, but didn't think it would be. I will try the various power conditioners in time.

    I suppose the final solution would be to run entire amp off DC battery through an inverter back to 120. I would be off my grid then. And if I still have noise, then an external, ambient source would be the most likely.

    fred
     
  18. Chris (throbbinut) is right, the Ampeg hum balance is just a pot on the filament lines. Won't hurt a thing to tweak it. I've been working too hard and got my amps mixed up! Like he said, Fender style amps use the hum balance as a bias control.
     
  19. fredsoffa

    fredsoffa

    Mar 2, 2003
    This is good to know, and now I will rest easier knowing I am not ruining amp. Amp now seems generally quiet, but occassionally takes a whole little run of 60 cycle noise coming through. Like every few minutes. Will attack that issue this weekend.

    Thanks again,
    fred