Decoupling (Tube) Amp from Speaker

Discussion in 'Amps and Cabs [BG]' started by beate_r, May 11, 2012.


  1. beate_r

    beate_r

    Jan 25, 2012
    Germany
    Hi people,

    this is mainly on my ancient small gig amplifier, but possibly also true for more or less all tube heads:

    [​IMG]

    This amplifier scratches due to the vibrations of the speaker. It sounds really well if placed on a separate desk. This of course restricts its usability in gigs, except for its original purpose (PA). For the curious: it is an Echolette M40 from 1963 running 4 EL84 at 32/40 Watts. In order to use it as a bass amp i am using a ECC81 in two of the input stages and (reversibly) removed the cathode capacitors of these stages in order to obtain more headroom.

    I have already cleaned the sockets and tightened their contacts - but this only improved the situation but did not entirely cure it. (Actually at least the master treble control is another potential source of buzz).

    In addition to slowly fixing the amp i think of decoupling it from the speaker - i actually belive it will need to decoupled even ifrom the stage.

    So my question to the others: Do You protect Your highly beloved vintage tops from the vibrations of the cabinet, which in any case may become strong?

    THX

    Beate
     
  2. I don't have those issues w/my mid 60s Fender Showman rig (2-15s) but if you are then you might consider putting a piece of foam between the head and the cabinet and see if that helps w/decoupling.
     
  3. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    If the cab vibrates that much it indicates inadequate bracing; rubber feet between it and the amp should be all the isolation you need. Inadequate bracing also causes lowered output, as energy that vibrates the cab doesn't end up coming out as sound. I'd fix the cause rather than the symptom.
     
  4. beate_r

    beate_r

    Jan 25, 2012
    Germany
    The real cause - contact problems in the amp - is something i am working to fix, but meanwhile i have almost given up the hope to obtain a complete fix, at least on short terms; so i am seeking a workaround i BTW: these 50 year old rubber feet have lost a lot of their elasticity...

    You are right - the internal bracing of that cabinet has a large potential to be improved and that will be done some day. But the problem also occurs with other, less vibrating speakers.

    Beate
     
  5. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    There are two types of speakers: those that don't vibrate and those that are defective. No speaker should vibrate so much that it causes the amp to rattle. I know many do, but they shouldn't.
    Replace them.
     
  6. Muziekschuur

    Muziekschuur

    May 25, 2009
    Stavenisse
    Those feet for the echolette can be found new I'm sure... Replace those and you'll have half a solution. Does the echolette have good tube restrainers? Maybe this will fix it. & some new tubes... If you open up the echolette. And tick against the glass of all the tubes. Do you hear a rinkel in the speaker? (For this the amplifier needs to be turned on and connected to the cabinet.... (so watch out with those voltages...)

    [​IMG]
     
  7. Stumbo

    Stumbo Guest

    Feb 11, 2008
    Bracing the cab is a pretty straight forward task and should not take much time. Glue and a few 1x2's should do it.
     
  8. Korladis

    Korladis Inactive

    Pretty much. I put my old (not as old as the OP's, but still 30 years old) tube amp on top of my cab when I play. So far I've not had any issues related to vibration, even at very high volumes.
     
  9. Primary

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    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.

     
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