Eden toroidal transformer buzz

Discussion in 'Amps and Cabs [BG]' started by slareman, Dec 28, 2007.


  1. slareman

    slareman

    Nov 7, 2007
    There was a thread on this about a year ago, but the issue was never resolved. I have a buzz coming from my Eden WT300 (upgraded to WT400 specs) that I can hear through speakers and also without anything (except the power cable) plugged into the amp. It seems to come directly from the toroidal transformer. The previous thread suggested loosening the bolt holding the transformer down and rotating it, but I have tried this and it has made the buzz coming through the speakers unbearably loud! Is it time for a new transformer? I was told that they are rather costly...

    Thanks!
     
  2. A9X

    A9X

    Dec 27, 2003
    Australia
    With no signal, ie the amp just turned on, the the buzz mainly mechanical, ie a vibration and/or does it also make sound through a speaker if connected? Does the buzz change in level if you adjust the volume control? Does the buzz change if you try the amp somewhere else?
     
  3. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Transformer windings can 'sing' if they aren't properly potted, but that's a mechanical vibration that normally cannot make its way into the signal path and can't be heard through the speakers. I'd look at other causes.
     
  4. seamonkey

    seamonkey

    Aug 6, 2004
    If it's coming through the speaker, has the tube become microphonic? If the transformer is humming, microphonics can pick this up.

    From the manual:

    "Tube Replacement – Tube life varies
    greatly depending upon use, vibration, and
    tube quality. It is uncommon for a tube to
    last less than a year in our circuits. Tube life
    of several years is not at all uncommon.
    Symptoms of tube failure include signal loss,
    distortion, and increased noise. The tube is
    easily replaced by removing the unit’s cover.
    Always disconnect the power cord from
    the back of the unit prior to removing the
    cover. Gently remove the tube and replace
    with a 7025 or high quality 12AX7 or
    equivalent tube."
     
  5. Maybe your filter caps are failing. Some guys use the lowest bidder on those. With that said, I have an 1,100 watt amp with a Toroid (Brand and shape) transformer in it. Noiseless after you throw the switch.

    If the amp has shielded cables on the inside, make sure they are grounded.

    Maybe your rectifier has had it?

    Those transformers are ALL noisy *dirty* power. It is the job of the amplifiers rectifier and caps to change the dirty AC into clean DC.

    Try this- Unplug the transformer from the main board. Look on the sticker on the trans and find the hot and ground wires (it will have multiple taps) Click it on and check the voltages with a volt meter and compare them to the spec sheet (on the trans). If it is vastly over or under, replace the transformer. Also make sure the input voltage is within the transformers spec (115v-120v)??
     
  6. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Good idea. I'd pull the pre tube, see if the power amp still transmits the hum.
     
  7. slareman

    slareman

    Nov 7, 2007
    Thanks for the tips guys. For the record, none of the knobs affect the buzz in any way, and it also happens plugged into different outlets.

    I replaced the preamp tube a few months ago, so I'm guessing that's not it either.

    bassmodder, thanks for the suggestion...I'll try checking the transformer input/output voltages.
     
  8. joegeezer

    joegeezer

    Mar 9, 2005
    Northern Wisconsin
    Avatar Club#12 Eden Club Lucky# 13--USA Peavey Club#37 Carvin Club#5
    This is why this is the greatest site going. Great information from intelligent, nice people, priceless. baby!! You guys all rock!
     
  9. A9X

    A9X

    Dec 27, 2003
    Australia
    I was wondering if it did it in different locations, such as rehearsal space or gigs. toroids get their efficiency increase by running very close to max flux density, so I've found some toroids will buzz in some locations due to a small amount of VLF hash often from industrial facilities on the same mains phase. If it doesn't do it in other locations, that might be a solution. Also check the wall voltage is correct; if it's high that'll have a similar effect.

    Otherwise, get it to a tech. If it's in the signal path it should be easy enough to trace.
     
  10. slareman

    slareman

    Nov 7, 2007
    The transformer doesn't say on it what the input/output voltages should be. It just has a tag that says "Talema" on it. Outlet is at 121.8 +/- 1.4 Volts (I have a cheap multimeter).

    I recorded a small sample of the buzz in case that would help the diagnosis:

    http://www.zshare.net/audio/604538366235c7/
     
  11. Wow. Sounds just like some ground loops I have had before... By any chance has the washer around your input jack rotted out?

    Take your meter, plug in a guitar cord and touch one lead to the sleeve of the guitar cord and the other end to the metal face plate of the amp. There should not be continuity. I had this happen on an amp once and it did the same thing yours is doing. Different brand though. Do you have any FX plugged into it? - I have had back feed through DI and preamp outs before-

    It should be totally silent with no guitar cord plugged into it as the preamp will short to ground- hence the muting with no cord.

    What happened when you removed the tube and powered the amp on?

    Can you try unplugging the preamp from the power amp board? -- High voltage from that tube-- Do not try messing with it with the amp plugged in--

    Is there any gooze leaking from around the filter cap area?
     
  12. I don't have specs for your amp either, but I would think you should have about 60 or so volts post rectifier. One will be + 60 and one will be - 60. Each one will be 1/2 of the AC sine wave. If you get that, I would think the trans and rectifier is ok.

    I am starting to run thin on suggestions for you without actually seeing the amp and its guts.

    Tech time might be getting close.
     
  13. slareman

    slareman

    Nov 7, 2007
    Oh! I powered on without the tube installed and the buzzing became a little deeper in pitch. But, when I unplug the preamp board, the sound pretty much disappears! So what does that mean? Thanks so much, I feel like this is some progress!

    BTW, I have no effects plugged in, no leaky caps, input washer is good, and there is no continuity between instrument cable jacket and amp front face.
     
  14. bassman639

    bassman639

    Dec 23, 2006
    northeast ,pa
    i had the wt550,brand new,had a hum ,loud loud loud,they said change the tube,did ok for awhile then started again, i went through three tubes, i sent it back, they said it was fixed ,when i got it, it was worse,so i sent it back again,well about 2 1/2 weeks later i got it back, wow works better than ever, they said the pre-amp board had to be replaced,you might want to check that too
     
  15. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    You've got a fault in the preamp, probably a bad ground. The liklihood that mechanical noise caused by a singing tranny could end up in the signal path is very slight, and it would take a component capable of turning a mechanical vibration into an electrical signal, like a microphonic tube, to do so. Having ruled that out you can now look around to find the bad ground.
     
  16. Considering the preamp is powerless when unplugged and the power amp is still hot (you should hear an ever so slight hiss from your speaker) The caps, rectifier, and tranney appear to be ok. With no tube where will be no preamplification so that rules out any possible tube combination causing your problems.

    So lets try this: Remove the preamp from the amp. Even the controller with the knobs on it. Lay a towel over the amp and lay the preamp on it. Plug it in and click it on. Does it buzz? If not, then something is shorting to chassis ground (which is dirty) in the signal path. If It still buzzes, and you see no bad components it will probably more worth your time to replace the preamp. I have fixed preamps like that but the time involved bacause I lack the tools and the training outweighs the money you will save fixing the board.

    Make sure no little chip "boobies" from your mod are not contacting anything odd on the back side of your board.
     
  17. I am sorry, should have been more clear: The "Ground" side of the 1/4" cable. Not the rubber sleeve.

    Please check the "long" part of the instrument cable for a short to chassis ground.

    Following the above advice in my last post will break any connection to ground on the preamp except for what is wired in by the manufacturer.
     
  18. slareman

    slareman

    Nov 7, 2007
    Sorry, I should have been more clear also...by "cable jacket" what I really meant was "cable barrel." I am aware that putting the probe on the rubber sleeve would not test anything!
     
  19. slareman

    slareman

    Nov 7, 2007
  20. You very well may have two problems going on in there or it is just the power amp input "floating" and picking up noise.

    I have also seen "cascade failure" where one component takes out another which takes out another. Happened in a very nice Crown amp of mine. I don't think this is the case with yours though.

    Maybe needs to have mosfet bias adjusted and the gains of the amplifiers adjusted. (There are atleast 3 amplifiers in your "amp") That will require an O scope and a tech who knows the test points along with a signal generator.

    Not exactly in the tools of the average guy. It would cost you more to acquire the tools and the knowledge rather than having a tech do it for you. If you do have a tech look at it, request that you be able to sit-in on the repair. It is almost a science (like body work on your car) and you WILL learn allot just by observing his process and how his tools work.

    I would not think you would really have to take it to an EDEN dealer, but rather a local electronics repair facility.

    It would REALLY help him or her if you could get:

    Service manual
    Parts Lists
    Diagrams of the Boards
    (Have this in paper form and clearly readable)
    A FULL description of what you were doing when the problem occurred and what you have done to it to try and remedy the problem.
     
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    Aug 1, 2021

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