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weird amp problem - power supply /wiring??

Discussion in 'Amps and Cabs [BG]' started by pbwalker30, Oct 29, 2013.


  1. pbwalker30

    pbwalker30

    Oct 29, 2013
    Hi guys was wondering if I could get your opinion on an issue.

    I've just emigrated to Australia from Ireland and have recently just got my furniture shipment from home.

    I've been pretty busy and only recently unpacked my music gear. I plugged in my trace Elliott combo for a quick play and noticed that that there was a slight buzzing/hissing coming from the amp. I also noticed that when i put my hands on the bass it went away. I had bought a second hand fender jazz in oz when I arrived to keep me busy so I kind of assumed (stupidly with hindsight) that this was the problem. Naturally enough I assumed it was a grounding issue and cracked open the bass and did the usual shielding, soldering etc.

    This did help somewhat but the noise was still there and was still annoying me. I then tried my p-bass the hiss was still there!

    I then assumed it was the amp or cables. I checked all my cables and they seem fine though the noise was less on my more expensive ones.

    Assuming it was the amp I then set up my Hartke rig only to discover the noise is still there!!!

    Out of annoyance and frustration I then went through my other basses. When I got to my stingray (my only active bass) the noise was completely gone. Experimenting I put my passive basses through the active input - no noise at all!!!

    I've no idea what the problem could be. It occurred to me that it could be a discrepancy in the amps power usage - though my hartke rig was bought in australia (i lived here before for a year whilst my wife was training) so that would seem to rule that out.

    The only thing that occurs to me is that the house wiring. We are renting until we can sell our house in ireland and the landlord had some problems with dodgy builders apparently. Is this even possible??

    it probably seems stupid - as the solution is just to plug into the active input and the loss of volume won't be an issue on a 500w rig- but this sort of thing just annoys me!

    Plus I had to leave my band to come here so its not like anybody else is going to notice!!

    Any advice/insight would be very much appreciated.
     
  2. Bassamatic

    Bassamatic keepin' the beat since the 60's Supporting Member

    If you've checked the grounding and shielding properly, it seems that there is some EMI radiation in your house wiring that is getting into the bass wiring and pickups. Can you check it somewhere else for comparison?

    Your old house may have had all the wiring in a metal conduit providing good shielding while the new house uses the unshielded type of wiring.

    I just noticed that you said "hiss" rather than "hum" or "buzz". Hiss can ONLY come from the amp.

    The guitar can only pick up the 50-60 Hz AC hum or buzz. Active guitars have a much lower impedance in the pickups and wiring making them more resistant to hum pickup as well as a stronger output level to decrease the effect of hum pickup in the cable.

    Any other strong EMI/RFI sources nearby? I used to do customer service for a wireless speaker company and one customer had a large radio station antenna close to his house causing all kinds of problems.

    Try it somewhere else first.

    Good luck with this.
     
  3. megafiddle

    megafiddle

    May 25, 2011
    As Bassamatic said, hiss comes from the amp.

    The hiss also seems to be there with a high impedance input condition (passive input,
    passive bass), and absent with a low impedance input condition (active input, active
    bass). So it certainly sounds like amp input noise.

    I can't offer any explanation as to why it is only occuring now though.

    Have you always used pedals before, or something that gave you low impedance, maybe?

    -
     
  4. pbwalker30

    pbwalker30

    Oct 29, 2013
    Thanks guys,

    I was being a bit generic describing the noise. Its more of a buzz really. I would have suspected the input too but the fact that its happening on both my combo and my stack suddenly suggests that its an external problem and the fact that its varies in strength significantly across all my basses from really bad (vintage p-bass) to bearable (jazzes) to non-existent (active sting-ray) probably bears that out.

    There is a television station with a massive dish - less than a km away - could that be it?

    thanks again guys
     
  5. Bowe

    Bowe

    Apr 1, 2013
    Italy
    The dish won't be the source of the buzz, but the broadcast antenna on a tower could cause your buzz. If your gear is picking up the transmission, which is very wide, it could sound like a buzz through an instrument, assuming you are near a digital transmission facility, it will change with the picture if it is analogue. The passive single-coil would be the worst, humbuckers would help a bit and actives will usually fare the best.

    Now for the real bad news;
    If the station engineer is a musician he/she could be a resource of assistance in mitigating it, but the best solution, if indeed it is the transmitter site, would be to relocate to a 'cooler' location (less RF).
     
  6. I live in Australia and recently moved house and in this new place I'm getting a lot more 50hz hum on single coil passive basses... My three actives are dead silent too... The worst is the SCPB which although it is well shielded, picks up hum that changes in intensity depending on the direction you are holding it... If I hold it up towards the ceiling I can almost work out the path of the wiring to the lights, and as they are down-lights with a transformer for each, there are four spots in the ceiling that are effectively hum generators... Very annoying. The pbass I have with barts is also quiet.
    I think you are suffering a similar issue, any down-lights in your place or dimmers ?
     
  7. pbwalker30

    pbwalker30

    Oct 29, 2013
    thanks again guys - you lot are awesome!

    I'd say conservatively there are 50 down lighters in this house (its brand new, big and kind of fancy) could that be the issue?

    I plugged in my pedal board and that lowered the buzz again. Though its still slightly there especially on my P.

    I may just be being picky - I am used to my gear only giving off the slightest of hums.

    I'm almost convinced its the wiring at this stage. I'm going to take the combo out of the house tomorrow and see what happens.

    Thanks again guys
     
  8. I'm guessing it is the down-lights... The four I mentioned are in one room I practice in, and also the rest of the house, I notice the hum in all rooms to varying degrees. Last house I didn't get hum nearly as bad (next to none). Each down-light usually has a step down transformer for the lower voltage down lights, and guess what ? They are also usually cheap and not shielded, so they pour out 50hz EM flux from the ceiling like a waterfall ;)

    Edit: after I moved, I also thought something was wrong with my gear until I thought about it, and did some testing, it was my active basses that also got me thinking...
     
  9. JellinWellen

    JellinWellen

    Oct 18, 2012
    Texas
    I'm having a very similar issue, holding the bass different directions and ESPECIALLY with the pickups facing the ceiling, light switches, or being close to my amplifier.
     
  10. abarson

    abarson

    Nov 6, 2003
    Santa Cruz
  11. The socket tester is a good idea as is trying the amp in a different room. If you stand too close to an amp with a regular power supply you will get interaction. Max both pickup volumes - the quietest position for a Jazz, and see if that helps any.

    May I wish you good fortune in your new land. I brought my family to Canada in '73. It was hard at first but we did succeed. :D
     
  12. JellinWellen

    JellinWellen

    Oct 18, 2012
    Texas
    I forgot to mention its a precision bass :cool:
     

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