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Minor Buzz In A 65 PRRI

Discussion in 'Glowing Bottle Tube Amp Forum' started by mom_said_im_cool, May 6, 2017.

  1. mom_said_im_cool

    mom_said_im_cool TDPRI Member

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    I've noticed on my new PRRI there is a weird buzz when I play very bassy pedals (EQD Bellows, Big Muff Pi, ETC) where I hear this sort of buzzing sound if I hold the note on certain frets. I notice it most on the 7th fret E, gets worse as I turn up the volume. It definitely sounds like something is vibrating in the amp.

    I've tried different rooms, putting it on something soft, etc. I've also tightened all 8 bolts inside the cab, the 4 nuts that hold on the speaker as well as the 4 bolts that support the chassis. They are all snug. For good measure I checked that all the tubes were seated and nothing else was loose.

    Seems like some sort of perfect pitch sets it off, it does happen on a few other frets too.

    Any ideas?
     
    Last edited: May 6, 2017
  2. brucerbc

    brucerbc TDPRI Member

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    I experienced the same thing with my PRRI a few years back. Check out this page: http://billmaudio.com/wp/?page_id=438 for some discussion and fix ideas. I think the newer PRRIs come with a reinforced baffle. A quick look should tell you yes or no. I ended up putting the "TO20 Low-Profile Output Transformer" in my PRRI as well (available from the same supplier - no affiliation): http://billmaudio.com/wp/?page_id=545. It tightened up the bottom end as promised. Best of luck. I think the PRRI is a great little amp.
     
  3. sockgtr

    sockgtr Tele-Meister

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    I leave the back panels off my PRRI. Helps clear up all sorts of rattles. Course, you have to exercise a bit additional caution moving it around as the tubes are exposed.
     
  4. Mistercharlie

    Mistercharlie Tele-Holic

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    Mine does that sometimes, but I always thought it was causing sideboard it sits on to rattle.
     
  5. mom_said_im_cool

    mom_said_im_cool TDPRI Member

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    Thanks! I must have been typing in the wrong keywords because I searched the issue before posting and then again after and found some of the resources referenced. TBH I'm not recording so if it's just a "charm" of the amp, I can live with it.

    Would make sense that it's in the baffle, I know this cabinet was tagged as completed in summer of 2016 IIRC and it does have the wood reinforcement bar up top.

    I'm definitely not going to go in and go through all the trouble of routing it and putting bars of aluminum in it. Would it be recommended to unscrew those 8 screws holding the baffle in and removing it carefully to inspect and re-seat it? Any risks to that?
     
  6. DennisM

    DennisM Tele-Meister

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    I have a FSR 65 PRRI Bordeaux with the 12" P12Q. I had a rattle/buzz problem with the low E on my LP. I too tightened things up but it still did it. I isolated it down to the metal tube protector cage. I tightened it down good but it still rattled. I removed the tube protector altogether and it went away. No more rattles and it sounds glorious.
     
  7. koko1

    koko1 TDPRI Member

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    Mine (PRRI65) had the rattle problem with the low F and the octave. Removing back panels helped. I was thinking of replacing the original back panels with thicker plywood. But I ended with a speaker replacement -> Celestion G10 Greenback. No more rattle at all and the slight mid hole of the stock Jensen is gone. There was a FSR-Version in mint-green with this speaker.
    This video was the trigger for changing ..



    I also put the stock Jensen in a stiffer constructed DIY-cab, just a little square box (in the size of a 12" speaker) with half open back and this combination gives very great clean sound due to a little less bass reproduction.
     
    Last edited: May 8, 2017
  8. mom_said_im_cool

    mom_said_im_cool TDPRI Member

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    Last night I was playing it and I found the offending note to be "C". I also noticed that when the buzz started, if I took my foot and put it against the top of the grille cloth and tilted the amp back, letting it rest it's weight on my foot the buzz stopped. This tells me that the issue is in the baffle.

    Oh well, I'm not recording. I may try and pull the baffle out if it becomes a bigger issue at volumes higher than 3. Rarely get to play it above 3.
     
  9. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    Do not pull ANYTHING apart if it's new! You might void the warranty. Take it in for service - it's nothing you'll haver to pay for. Do not do anything yourself unless you know exactly what you are going to "fix" and which parts you can remove without voiding the warranty.
     
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