Strange Metallic Whistle in Rivera (sample)

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by rbuono, Jan 31, 2006.

  1. rbuono

    rbuono Member

    Messages:
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    Sep 30, 2005
    Hi,

    I know it's probably a long shot but I was hoping for some advice on this.

    I've had this problem with a Rivera 55 12 for a while now and it hasn't really been too much trouble since it doesn't always make itself audible. I was messing with the amp today and decided to see if I could capture it so someone else could hear. Please take a listen (Metallic Whistle) and let me know if you have any ideas. It is worse with the master cranked. It seems to be sensitive to certain note frequencies. Other than this the amp works great. I just want to make this problem go away. At first I thought it was filament rattle but I changed tubes out and it stayed. I think it is somehow connected with a vibration on the power tube socket board. It seems like when I put pressure on the power tubes or socket it diminishes. It's not usually too audible at my regular settings but still shouldn't be there. Oh also, it goes completely away when using an extension cab so it's not in the electronics per se. Thanks for any suggestions or advice. If anyone knows a Rivera tech in the NYC area please let me know.
    THANKS

    http://www.soundclick.com/bands/pagemusic.cfm?bandID=415528
     
  2. Shea

    Shea Member

    Messages:
    540
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    Sep 7, 2004
    I agree it's probably a vibration. From what you've said, it sounds like the vibration is happening around the power tubes. Do they feel tight in their sockets? If not, then maybe retensioning the contacts in the sockets would help. Also, if the sockets are PCB mounted, then see if the PCB is a little loose, and check for bad solder joints where the sockets are mounted to the PCB. Discharge the filter caps first, of course.

    Shea
     
  3. rbuono

    rbuono Member

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    Sep 30, 2005
    Thanks Shea. The contacts are tight - a little too tight which might have caused the other possible situation of broken joints. The tubes take a bit of back and forth to get them out - they are in there very tight. The sockets are PCB mounted and I will tighten the board.

    I am going to have a tech check it out since I don't know how to do any of that testing or repair. I can bias the amp but I'm not comfortable doing anything else.
     
  4. sixstringslut

    sixstringslut Member

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    529
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    Dec 22, 2005
    You might want to take a look at the physical placement of some components, like two caps touching. Or wire placement. Gently moving suspect parts away from each other.
     
  5. Shea

    Shea Member

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    540
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    Sep 7, 2004
    Yeah, don't risk doing anything yourself that don't feel comfortable doing.

    I couldn't listen to your clip very loudly at work, but from what I could make out, it sounded similar to a problem I had with a Twin Reverb, where some parts were vibrating sympathetically and their vibrations were getting amplified by microphonic parts. There were a few things I had to fix to get rid of it.

    Shea
     

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