PRRI 68 Sounds Muffled

Discussion in 'Amp Central Station' started by pagedr, Feb 26, 2020.

  1. pagedr

    pagedr TDPRI Member

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    Just bought a new PRRI 68 online and it sounds really muffled unless I have the treble cranked up. With my Teles and Strat the treble can be around 6-7 or so and it sounds ok, but I have an ES-125 with P90s and it has to be set to 10 or else it doesn’t sound good, and I can’t even get a serviceable tone for my 335.

    I’ve played these amps before, although only with Teles, and never noticed this issue. I also pretty much only buy used amps, is this just part of the speaker break in process? Or is something else going on?
     
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  2. Dacious

    Dacious Poster Extraordinaire

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    Where is your volume and bass set? Humbucker and possibly P90 guitars you're often better with a PR putting them in input 2.
     
  3. pagedr

    pagedr TDPRI Member

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    V
    Yeah I’ve been mainly sticking with input 2 so far. Volume is around 5-6, bass around 3-4 but I’ve been messing with a few different settings as well.
     
  4. Axegrinder77

    Axegrinder77 Tele-Holic

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    Your ears will adjust, then everything else will sound thin.

    Get an eq pedal. That will get you by.

    Oh, and these amps are worthy of a speaker upgrade.

    I threw a g10v in mine. Then, even better, got a 1x12 cab.
     
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  5. Dacious

    Dacious Poster Extraordinaire

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    Two tips: one is that the FMV tone stack the treble acts like a second volume control for all frequency bands. Mids are fixed by a resistor, but as volume goes over 5 treble is usually 6 max. Depending on guitar, you can otherwise find that you start getting trebly harshness and flubby bass.

    On the Princeton, a factor is the dinky output transformer, and what is basically a Champ power supply. The split tail.phase inverter which is a throwback to Tweeds also makes it sensitive to eqs. If your guitars are always at 10 on volume this bears remembering.

    Also the 68 Custom PRRI has reduced global negative feedback and the changed Celestion speaker also impacts the tone - some like the greater mids, some don't. If you want more clarity and headroom I'd look at the 65 PRRI if you have a return opportunity.

    I had a SF PR I ran my 335 through and dropping bass slightly over Strat or Tele was necessary to clean it up.
     
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  6. jsnwhite619

    jsnwhite619 Friend of Leo's

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    It comes with a Celestion I think? I've never heard a Celestion/Fender combo that I thought sounded like a Fender should. The '68 has reduced Negative Feedback and the Celestion to try to take them more into rocker territory. The NFB isn't a bad choice, but a $25 Chinese Celestion - regardless of what they charge for it - just isn't going to have the Princeton tone you were expecting.

    Probably needs some break-in time, but I'd list the Celestion and get a Legend 1058 for it.
     
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  7. noname_dragon

    noname_dragon Tele-Meister

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    The EMI GA10-SC64 is fantastic for an authentic PR tone
     
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  8. MilwMark

    MilwMark Doctor of Teleocity Ad Free Member

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    Input 2 is muffled. Use input 1.

    Put the Bass on 0.

    Treble on 10.

    Adjust from there with your ears, not your eyes.
     
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  9. jsnwhite619

    jsnwhite619 Friend of Leo's

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    Do those amps have a bias pot? If so, I've always thought that a cooler bias clears up and brightens up a Fender.
     
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  10. tah1962

    tah1962 Tele-Holic

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    Here are some easy mods I did on my 68 Custom Princeton Reverb that really cleaned up the tone.
    • Look online for the bass mod. You basically run a jumper wire to take the R34 18k resistor out of the circuit. Note: If you’ve never worked on a tube amp take it to a tech. There is deadly voltage in the filter capacitors. You must drain them before you ever start poking around in the chassis.
    • Put a 12AY7 preamp tube in V3
    • Change your speaker to an Eminence Alessandro GA10SC64.
    You will actually be able to reduce treble and increase bass. Prior to the mod, I always had the bass knob no higher than 1, and the treble knob around 8-9. After the mod, I run treble around 6-7, and bass around 4-5. These mods really open up the eq on the amp. Hope this helps.
     
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  11. tah1962

    tah1962 Tele-Holic

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    Yes, there is a bias pot on these amps. I recently put new 6v6 power tubes in mine and re-biased. I ended up setting bias a little over 19 mA. That has the tubes running around 70% dissipation. Running colder than that made the amp sound sterile.
     
  12. noname_dragon

    noname_dragon Tele-Meister

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    Not sure how this relates... I found the true voice of any bass/treble BF/SF Fender amp is found by turning both tone controls all the way down, and turning the volume up. Then add treble and bass as needed.
    Let the disagreements begin
     
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  13. Marc Morfei

    Marc Morfei Tele-Afflicted

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    Yup. That's what it sounds like. I ended up swapping mine for a 65.
     
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  14. chris302

    chris302 TDPRI Member

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    I liked the Princeton 68 as it was, but I was curious to try the resistor mod. The tonal difference is quite significant and the bass control now offers a wider range of bass.

    This is maybe the cheapest way for OP to solve its issue.
     
    Last edited: Feb 27, 2020
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  15. muchxs

    muchxs Doctor of Teleocity

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    I've worked on a ton of original Princeton Reverbs. The '68 Customs are getting old enough I'm starting to see those.

    "Dull sounding"?


    It's a used amp. What does it have for a speaker?

    Maybe imported Celestion speakers come with socks stuffed in the speaker motor.

    If Axegrinder wasn't a moped rider he'd be my new customer service representative. "Your ears will adjust."



    I'd go for tubes first. Make sure the amp is right and the right tubes are in the right slots. Seems something isn't right.

    It might be worthwhile to see if there aren't internal production errors.

    I use the low input for clean tones, high input for overdrive. But... all my Princeton Reverbs are modified, the real "'69 Customs".

    Turn the bass up by feel. There a spot low on the dial where the tone fattens up. That's where you want to be.

    Turning the treble all the way up makes as much sense as turning the treble all the way up on a Twin. If you're not in a Johnny Cash tribute band... don't do that.

    My Princeton Reverb plays clear, tight and clean with a 12AX7 in V3.
    Reissues have bias pots. Originals don't.
     
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  16. MilwMark

    MilwMark Doctor of Teleocity Ad Free Member

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    Normally with a BF/SF Fender I’d agree with you. But the ‘68 CPR is voiced darker to my ear. So when I used one live I set the Bass on 0 or 1, maybe 2. And the Treble in 7-8 (unheard of for me).

    I wouldn’t expect the OP to end up at 10 but starting there rather than “noon” might be helpful in this case.
     
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  17. pagedr

    pagedr TDPRI Member

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    Appreciate all of the insights, everyone! As mentioned it is a brand new amp so I'm gonna give the speaker some more time to open up and myself some more time to get used to it/figure out how to get the sound I want. Worst case, I got a really good deal on it from a shop that was closing so I'm sure I could trade it in to a local shop for a '65 and more or less get my money back on it.
     
  18. 8trackmind

    8trackmind Tele-Holic

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    I've done the bass mod and a speaker swap on my 68 PR custom. Sounds great with Tele's and Strats. Mine sounds a bit dull with hot P90 equipped semi- hollows but gets along with les pauls. It really is voiced to compensate for the lack of mids. I run the bass about 2 and the treble on 6 or 7 with a Telecaster/stratocaster.
     
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  19. ce24

    ce24 Poster Extraordinaire

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    Send it to muchxs!:D
     
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  20. Bluey

    Bluey Tele-Meister

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    Someone somewhere mentioned their brand new 68 Custom PRRI had some tubes in the wrong position so it may pay to check. Never liked the original celestion 10/30 I think it was and finally settled on a 10" Gold messed about with tubes a bit also and settled on a nos GE 5751in V1the rest back to stock. Wouldnt mind a 3 way NFB switch mod but maybe one day. The 65 Princeton did nothing for me so I went with the 68 Custom and now glad I did.
     
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